HEAT EXCHANGER

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of International Patent Application No. PCT/JP2024/009848 filed on Mar. 13, 2024, which designated the U.S. and claims the benefit of priority from Japanese Patent Application No. 2023-041658 filed on Mar. 16, 2023. The entire disclosures of all of the above applications are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a heat exchanger.

BACKGROUND

A previously proposed heat exchanger includes a plurality of tubes, a first header tank and a second header tank. The tubes conduct a refrigerant and are arranged in a first row and a second row. The tubes in the first row and the tubes in the second row are exposed in the first header tank and the second header tank. A longitudinal partition is provided in the first header tank to divide the first header tank along a longitudinal direction into a refrigerant inlet chamber, in which the tubes in the first row are exposed, and a refrigerant outlet chamber, in which the tubes in the second row are exposed.

SUMMARY

According to the present disclosure, there is provided a heat exchanger that may include a primary header tank, a plurality of primary tubes, a primary turn tank, a secondary turn tank, a plurality of secondary tubes and a secondary header tank. The primary header tank may be configured to receive a refrigerant in a superheated gas state from an upstream-side flow passage located on an upstream side of the heat exchanger in a flow direction of the refrigerant. The plurality of primary tubes may be configured to receive the refrigerant distributed from the primary header tank. The primary turn tank may be configured to receive the refrigerant from the plurality of primary tubes. The secondary turn tank may be configured to receive the refrigerant from the primary turn tank. The plurality of secondary tubes may be configured to receive the refrigerant distributed from the secondary turn tank. The secondary header tank may be configured to receive the refrigerant in a subcooled liquid state from the plurality of secondary tubes and then output the refrigerant into a downstream-side flow passage located on a downstream side of the heat exchanger in the flow direction of the refrigerant. An internal flow path, which extends from the plurality of primary tubes to the plurality of secondary tubes via the primary turn tank and the secondary turn tank, may have a primary region and at least one secondary region that are arranged one after another in a stacking direction, in which the plurality of primary tubes are stacked and the plurality of secondary tubes are stacked. A pressure loss of the primary region and a pressure loss of the at least one secondary region may be different from each other when a flow rate of the refrigerant in the primary region is the same as a flow rate of the refrigerant in the at least one secondary region.

BRIEF DESCRIPTION OF DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is a perspective view showing an overall structure of a heat exchanger according to a first embodiment.

FIG. 2 is a perspective view showing the heat exchanger illustrated in FIG. 1 in an exploded state.

FIG. 3 is a plan view showing the heat exchanger illustrated in FIG. 2 in a developed state.

FIG. 4 is a view showing (A) a cross-section taken along line IVA-IVA of FIG. 3 and (B) a cross-section taken along line IVB-IVB in FIG. 3.

FIG. 5 is a p-h diagram in which a refrigeration cycle is illustrated.

FIG. 6 is a plan view showing a heat exchanger of a comparative example in a developed state.

FIG. 7 is a plan view showing the heat exchanger of the comparative example in the developed state.

FIG. 8 is a view showing (A) a cross-section of a structure of a secondary turn tank of the comparative example and (B) a cross-section of a structure of a primary turn tank of the comparative example.

FIG. 9 is a plan view showing a modification of the heat exchanger of the first embodiment in a developed state.

FIG. 10 is a plan view showing a heat exchanger of a second embodiment in a developed state.

FIG. 11 is a plan view showing a heat exchanger of a third embodiment in a developed state.

FIG. 12 is a view showing (A) a cross-section taken along line VIIIA-VIIIA of FIG. 11 and (B) a cross-section taken along line VIIIB-VIIIB in FIG. 11.

FIG. 13 is a plan view showing a heat exchanger of a fourth embodiment in a developed state.

FIG. 14 is a view showing (A) a cross-section taken along line XA-XA of FIG. 13 and (B) a cross-section taken along line XB-XB in FIG. 13.

FIG. 15 is a cross-sectional view showing a structure of a secondary turn tank of the heat exchanger of the fourth embodiment.

FIG. 16 is a plan view showing a heat exchanger of a fifth embodiment in a developed state.

FIG. 17 is a diagram showing examples of a tube used in the heat exchanger illustrated in FIG. 16.

FIG. 18 is a plan view showing a heat exchanger of a sixth embodiment in a developed state.

FIG. 19 is a perspective view showing an overall structure of a heat exchanger of a seventh embodiment.

FIG. 20 is a cross-sectional perspective view of a turn tank illustrated in FIG. 19.

FIG. 21 is a view showing (A) a cross-section taken along line XVIA-XVIA in FIG. 20 and (B) a cross-section taken along line XVIB-XVIB in FIG. 20.

FIG. 22 is a cross-sectional view showing a modification of FIG. 21.

FIG. 23 is a graph showing a relationship between Nsc/Nall and a left-right temperature difference ΔT of air blown out from the heat exchanger.

FIG. 24 is a graph showing a relationship between a total opening cross-sectional area AS of communication holes and a pressure loss PL of the refrigerant.

DETAILED DESCRIPTION

A previously proposed heat exchanger includes a plurality of tubes, a first header tank and a second header tank. The tubes conduct a refrigerant and are arranged in a first row and a second row. The tubes in the first row and the tubes in the second row are exposed in the first header tank and the second header tank. A longitudinal partition is provided in the first header tank to divide the first header tank along a longitudinal direction into a refrigerant inlet chamber, in which the tubes in the first row are exposed, and a refrigerant outlet chamber, in which the tubes in the second row are exposed.

When the heat exchanger is used as a condenser in a refrigeration cycle, a superheated gas refrigerant flowing into the heat exchanger undergoes heat exchange, goes through a gas-liquid two-phase state, and flows out as a subcooled liquid refrigerant. When the above-described heat exchanger is used as the condenser, the superheated gas refrigerant flows into the refrigerant inlet chamber and is subjected to heat exchange while passing through the tubes in the first row, thereby becoming the refrigerant in the gas-liquid two-phase state. Thereafter, the refrigerant is further subjected to heat exchange while passing through the tubes in the second row via the second header tank, and then the refrigerant reaches the refrigerant outlet chamber as the subcooled liquid refrigerant. The tubes in the first row and the tubes in the second row are arranged on the upstream side and the downstream side, respectively, with respect to a flow direction of the airflow. Therefore, for example, in a case where the condenser is used in a heating apparatus for heating a vehicle cabin, the tubes in the second row, through which the subcooled liquid refrigerant having the low temperature flows, and the tubes in the first row, through which the superheated gas refrigerant having the high temperature flows, are arranged to overlap in the flow direction of the airflow so that the temperature of the air discharged from the condenser is adjusted to become uniform along the condenser.

In the above-described heat exchanger, the superheated gas refrigerant, which flows into the refrigerant inlet chamber, is passively distributed along the longitudinal direction of the refrigerant inlet chamber and flows into the tubes in the first row. Therefore, when the longitudinal length of the refrigerant inlet chamber is increased, a pressure loss in the refrigerant inlet chamber increases, and a flow rate of a shortcut flow of the refrigerant near the inlet, where the superheated gas refrigerant flows into the refrigerant inlet chamber, is increased. As a result, the amount of the superheated gas refrigerant, which reaches the side opposite to the inlet of the refrigerant inlet chamber, is decreased, and deterioration in the temperature distribution in a tube stacking direction, in which the tubes are stacked, is expected.

According to one aspect of the present disclosure, there is provided a heat exchanger that includes: a primary header tank that is configured to receive a refrigerant in a superheated gas state from an upstream-side flow passage located on an upstream side of the heat exchanger in a flow direction of the refrigerant; a plurality of primary tubes that are configured to receive the refrigerant distributed from the primary header tank; a primary turn tank that is configured to receive the refrigerant from the plurality of primary tubes; a secondary turn tank that is configured to receive the refrigerant from the primary turn tank; a plurality of secondary tubes that are configured to receive the refrigerant distributed from the secondary turn tank; and a secondary header tank that is configured to receive the refrigerant in a subcooled liquid state from the plurality of secondary tubes and then output the refrigerant into a downstream-side flow passage located on a downstream side of the heat exchanger in the flow direction of the refrigerant. An internal flow path, which extends from the plurality of primary tubes to the plurality of secondary tubes via the primary turn tank and the secondary turn tank, has a primary region and at least one secondary region that are arranged one after another in a stacking direction, in which the plurality of primary tubes are stacked and the plurality of secondary tubes are stacked. A pressure loss of the primary region and a pressure loss of the at least one secondary region are different from each other when a flow rate of the refrigerant in the primary region is the same as a flow rate of the refrigerant in the at least one secondary region.

Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components are indicated by the same reference signs as much as possible in each drawing, and redundant descriptions are omitted.

As shown in FIG. 1, a heat exchanger 2 includes a primary header tank 21, a primary core 22, a primary turn tank 23, a secondary turn tank 24, a secondary core 25 and a secondary header tank 26. The heat exchanger 2 is configured to perform heat exchange between air, which serves as a first fluid, and a refrigerant, which serves as a second fluid. The heat exchanger 2 is used, for example, as a condenser for heating a cabin of a vehicle. The heat exchanger 2, serving as the condenser, is incorporated into a refrigeration cycle (not shown). The heat exchanger 2, which is incorporated into the refrigeration cycle, is connected to an upstream-side flow passage, which is located on an upstream side of the heat exchanger 2 in a flow direction of the refrigerant, and a downstream-side flow passage of the refrigeration cycle, which is located on downstream side of the heat exchanger 2 in the flow direction of the refrigerant.

The primary header tank 21 has a flow inlet 211. The flow inlet 211 is configured to receive the refrigerant (serving as the second fluid) from the upstream-side flow passage of the refrigeration cycle. The refrigerant, which is supplied into the flow inlet 211, flows into the primary header tank 21. The refrigerant, which is supplied into the primary header tank 21, flows into the primary core 22. The refrigerant, which is supplied into the primary core 22, exchanges heat with the air (serving as the first fluid) and flows into the primary turn tank 23.

The refrigerant, which is supplied into the primary turn tank 23, flows into the secondary turn tank 24. The refrigerant, which is supplied into the secondary turn tank 24, flows into the secondary core 25. The refrigerant, which is supplied into the secondary core 25, exchanges heat with the air (serving as the first fluid) and flows into the secondary header tank 26.

The secondary header tank 26 has a flow outlet 261. The flow outlet 261 is configured to discharge the refrigerant into the downstream-side flow passage of the refrigeration cycle. The refrigerant, which is supplied into the secondary header tank 26, is discharged from the flow outlet 261 into the downstream-side flow passage.

In FIG. 1, a direction, in which the air flows through the primary core 22 and the secondary core 25, is defined as an x-direction, and an x-axis is set along the x-direction. In addition, a direction, which is perpendicular to the x-direction and is a longitudinal direction of each of the primary header tank 21, the secondary header tank 26, the primary turn tank 23 and the secondary turn tank 24, is defined as a y-direction, and a y-axis is set along the y-direction. In addition, a direction, which is perpendicular to both the x-direction and the y-direction, is defined as a z-direction. The z-direction is directed from the lower side toward the upper side in FIG. 1 and is directed from the primary turn tank 23 toward the primary header tank 21 and is also directed from the secondary turn tank 24 toward the secondary header tank 26. Furthermore, a z-axis is set along the z-direction. In the following description, the x-direction, the y-direction and the z-direction defined above are used. It should be noted that the z-direction is a direction from the lower side toward the upper side in FIG. 1, and this direction does not necessarily correspond to the vertical direction in an actual installation. Accordingly, when the heat exchanger 2 is installed in a vehicle, the primary header tank 21 and the secondary header tank 26 may be disposed on the lower side in the vertical direction, and the primary turn tank 23 and the secondary turn tank 24 may be disposed on the upper side in the vertical direction.

FIG. 2 is a perspective view illustrating the inside of the heat exchanger 2 shown in FIG. 1 in an exploded manner. FIG. 2 illustrates a state in which the primary header tank 21, the primary core 22 and the primary turn tank 23 are separated from the secondary header tank 26, the secondary core 25 and the secondary turn tank 24, and are rotated 90 degrees about the Z-axis from the state shown in FIG. 1. The XYZ axes for the primary header tank 21, the primary core 22 and the primary turn tank 23 are shown in the vicinity of the primary header tank 21, the primary core 22 and the primary turn tank 23. The XYZ axes for the secondary header tank 26, the secondary core 25 and the secondary turn tank 24 are shown in the vicinity of the secondary header tank 26, the secondary core 25 and the secondary turn tank 24.

The primary core 22 includes a plurality of primary tubes 221, a plurality of primary fins 222 and a pair of side plates 223. Each of the primary tubes 221 is configured to conduct the second fluid, which is the refrigerant, through the inside thereof. One end of each of the primary tubes 221 is in communication with the inside of the primary header tank 21, and the other end of each of the primary tubes 221 is in communication with the inside of the primary turn tank 23. The primary tubes 221 and the primary fins 222 are alternately stacked. The pair of side plates 223 are provided to hold the primary tubes 221 and the primary fins 222, which are stacked in a stacking direction, between the pair of side plates 223 in the stacking direction.

The primary fins 222 are bent in a wavy shape. The primary fins 222 form air flow passages through which the air (the first fluid) flows. A refrigerant flow passage through which the refrigerant (the second fluid) flows is provided inside each primary tube 221. Each primary fin 222 is in contact with the adjacent primary tubes 221 and is configured to allow heat exchange therebetween. Accordingly, each primary fin 222 and the adjacent primary tubes 221 are configured to enable heat exchange between the air flowing along the primary fin 222 and the refrigerant flowing through the primary tubes 221.

The primary turn tank 23 includes a partition wall 23w. The partition wall 23w is a wall that contacts the secondary turn tank 24. The partition wall 23w has a plurality of communication holes 23f1, 23f2, 23c1, 23c2, 23c3, 23c4, 23r1, 23r2 which extend through the partition wall 23w. The communication holes 23f1, 23f2, 23c1, 23c2, 23c3, 23c4, 23r1, 23r2 are configured to conduct the refrigerant therethrough.

All of the communication holes 23f1, 23f2, 23c1, 23c2, 23c3, 23c4, 23r1, 23r2 have an identical circular shape. It should be noted that the communication holes 23f1, 23f2, 23c1, 23c2, 23c3, 23c4, 23r1, 23r2 are all illustrated as having the identical circular shape merely for the sake of explanation, and the shape of the communication holes is not particularly limited. For example, the communication holes may take various shapes, including semicircular or rectangular shapes.

The communication holes 23f1, 23f2 are included in a secondary region Tf. The communication holes 23c1, 23c2, 23c3, 23c4 are included in a primary region Tc. The communication holes 23r1, 23r2 are included in a secondary region Tr. The number of the communication holes 23f1, 23f2 formed in the secondary region Tf is smaller than the number of the communication holes 23c1, 23c2, 23c3, 23c4 formed in the primary region Tc. The number of the communication holes 23r1, 23r2 formed in the secondary region Tr is smaller than the number of the communication holes 23c1, 23c2, 23c3, 23c4 formed in the primary region Tc. In terms of a ratio of opening cross-sectional areas of the communication holes 23f1, 23f2, 23c1, 23c2, 23c3, 23c4, 23r1, 23r2 relative to a surface area of the partition wall 23w, an opening ratio of the primary region Tc is larger than an opening ratio of the secondary region Tf and is also larger than an opening ratio of the secondary region Tr. A pressure loss in each of the pair of secondary regions Tf, Tr is higher than a pressure loss in the primary region Tc, and the primary region Tc is interposed between the pair of secondary regions Tf, Tr.

The secondary turn tank 24 includes a partition wall 24w. The partition wall 24w is a wall that contacts the primary turn tank 23. The partition wall 24w has a plurality of communication holes 24f1, 24f2, 24c1, 24c2, 24c3, 24c4, 24r1, 24r2 which extend through the partition wall 24w. The communication holes 24f1, 24f2, 24c1, 24c2, 24c3, 24c4, 24r1, 24r2 are configured to conduct the refrigerant therethrough. All of the communication holes 24f1, 24f2, 24c1, 24c2, 24c3, 24c4, 24r1, 24r2 have an identical circular shape.

The communication holes 24f1, 24f2 are included in the secondary region Tf. The communication holes 24c1, 24c2, 24c3, 24c4 are included in the primary region Tc. The communication holes 24r1, 24r2 are included in the secondary region Tr. The number of the communication holes 24f1, 24f2 formed in the secondary region Tf is smaller than the number of the communication holes 24c1, 24c2, 24c3, 24c4 formed in the primary region Tc. Also, the number of the communication holes 24r1, 24r2 formed in the secondary region Tr is smaller than the number of the communication holes 24c1, 24c2, 24c3, 24c4 formed in the primary region Tc. In terms of a ratio of opening cross-sectional areas of the communication holes 24f1, 24f2, 24c1, 24c2, 24c3, 24c4, 24r1, 24r2 relative to a surface area of the partition wall 24w, an opening ratio of the primary region Tc is larger than an opening ratio of the secondary region Tf and is also larger than an opening ratio of the secondary region Tr. A pressure loss in each of the pair of secondary regions Tf, Tr is higher than a pressure loss in the primary region Tc, and the primary region Tc is interposed between the pair of secondary regions Tf, Tr.

In a state where the partition wall 23w is in contact with the partition wall 24w, the communication hole 23f1 in the secondary region Tf is in communication with the communication hole 24f1. Similarly, the communication hole 23f2 is in communication with the communication hole 24f2. In the primary region Tc, the communication hole 23c1 is in communication with the communication hole 24c1. Similarly, the communication hole 23c2 is in communication with the communication hole 24c2, the communication hole 23c3 is in communication with the communication hole 24c3, and the communication hole 23c4 is in communication with the communication hole 24c4. In the secondary region Tr, the communication hole 23r1 is in communication with the communication hole 24r1, and the communication hole 23r2 is in communication with the communication hole 24r2.

Hereinafter, as shown in FIG. 3, a region of the secondary region Tf, in which the communication holes 23f1, 23f2, 24f1, 24f2 are provided, is referred to as a secondary outer region Tf1, and a remaining region of the secondary region Tf, which is other than the secondary outer region Tf1, is referred to as a secondary inner region Tf2. Furthermore, a region of the secondary region Tr, in which the communication holes 23r1, 23r2, 24r1, 24r2 are provided, is referred to as a secondary outer region Tr1, and a remaining region of the secondary region Tr, which is other than the secondary outer region Tr1, is referred to as a secondary inner region Tr2. The secondary inner region Tf2 is interposed between the secondary outer region Tf1 and the primary region Tc, and the secondary inner region Tr2 is interposed between the secondary outer region Tr1 and the primary region Tc. The primary region Tc is interposed between the secondary region Tf and the secondary region Tr.

FIG. 3 is a plan view showing, in an unfolded planar form, the heat exchanger 2 that is shown in a perspective view in FIG. 2. Similar to FIG. 2, the XYZ axes for the primary header tank 21, the primary core 22, and the primary turn tank 23 are shown in the vicinity of the primary header tank 21, the primary core 22 and the primary turn tank 23. The XYZ axes for the secondary header tank 26, the secondary core 25 and the secondary turn tank 24 are shown in the vicinity of the secondary header tank 26, the secondary core 25 and the secondary turn tank 24.

(A) in FIG. 4 is a cross-sectional view showing a cross-sectional structure taken along line IVA-IVA in FIG. 3. (B) in FIG. 4 is a cross-sectional view showing a cross-sectional structure taken along line IVB-IVB in FIG. 3. As shown in (B) in FIG. 4, the entire interior of the primary turn tank 23 is continuous in the Y-direction, which is the longitudinal direction. As shown in (A) in FIG. 4, the entire interior of the secondary turn tank 24 is also continuous in the Y-direction, which is the longitudinal direction of the secondary turn tank 24.

The refrigeration cycle will be described with reference to FIG. 5. FIG. 5 is a p-h diagram in which pressure p is plotted on the vertical axis, and enthalpy h is plotted on the horizontal axis, and the refrigeration cycle is illustrated thereon. In FIG. 5, a section of a curve, which is located on the left side of a critical point P10, is referred to as a saturated liquid line M11, and another section of the curve, which is located on the right side of the critical point P10, is referred to as a saturated vapor line M12. As shown in FIG. 5, the refrigeration cycle includes a compression process, a condensation process, an expansion process and an evaporation process.

The compression process is a process where the refrigerant gas evaporated in the evaporation process is compressed to become the superheated gas refrigerant which has the high temperature and the high pressure. The condensation process is a process where heat is removed from the superheated gas refrigerant to convert it into a subcooled liquid refrigerant. The expansion process is a process where the pressure of the subcooled liquid refrigerant, which has the high pressure, is reduced. The evaporation process is a process where heat is applied to the liquid refrigerant to evaporate it.

For example, an evaporator is a heat exchanger used in the evaporation process of the refrigeration cycle shown in FIG. 5. The refrigerant in a gas-liquid two-phase state, which is generated in the expansion process, is supplied into the evaporator. In the evaporator, the refrigerant in the gas-liquid two-phase state exchanges heat with the air, whereby the state of the refrigerant changes as indicated by an arrow L11. That is, the refrigerant in the gas-liquid two-phase state absorbs heat from the air and changes into a gas-phase refrigerant, which remains at a low temperature and low pressure. An intersection point, at which the arrow L11 and the saturated vapor line M12 intersect, indicates a point where the state of the refrigerant changes from the gas-liquid two-phase state to the gas state. As described above, only two states of the refrigerant, namely the gas-liquid two-phase state and the gas state, basically exist in the evaporator. Therefore, when attempting to equalize the temperature distribution of the air blown from the evaporator, it is generally sufficient to equalize the refrigerant flow rate in the region of the evaporator where the refrigerant is in the gas state, that is, the so-called superheated gas region.

With respect to this point, the heat exchanger 2 of the present embodiment shown in FIGS. 1 to 4 functions as the condenser that performs the condensation process. Accordingly, the refrigerant, which becomes the gas state through the compression process and thereby has the high temperature and the high pressure, flows into the heat exchanger 2. In the heat exchanger 2, the refrigerant in the gas state exchanges heat with the air, whereby the state of the refrigerant changes as indicated by an arrow L12. That is, as the refrigerant in the gas state releases the heat to the air, the state of the refrigerant sequentially changes from the gas state to the gas-liquid two-phase state and then to the liquid state. An intersection point, at which the arrow L12 and the saturated vapor line M12 intersect, indicates a point where the state of the refrigerant changes from the gas state to the gas-liquid two-phase state. An intersection point, at which the arrow L12 and the saturated vapor line M11 intersect, indicates a point where the state of the refrigerant changes from the gas-liquid two-phase state to the liquid state. Thus, three states of the refrigerant, namely the gas state, the gas-liquid two-phase state, and the liquid state, are present in the heat exchanger 2. Therefore, when attempting to equalize the temperature distribution of the air blown from the heat exchanger 2, it is necessary not only to equalize the refrigerant flow rate in the region of the heat exchanger 2 where the refrigerant is in the gas state, namely the so-called superheated gas region, but also to equalize the refrigerant flow rate in the region of the heat exchanger 2 where the refrigerant is in the liquid state, namely a subcooled liquid region. In other words, in the heat exchanger 2, the temperature distribution of the air, which is ultimately discharged from the heat exchanger 2, results from the superimposition of the temperature distribution of the air in the superheated gas region and the temperature distribution of the air in the subcooled liquid region. Therefore, in order to make the temperature distribution of the air discharged from the heat exchanger 2 uniform, it is important to adjust the positional relationship between the superheated gas region and the subcooled liquid region in the heat exchanger 2. Thus, the heat exchanger 2 of the present embodiment, which functions as the condenser, has a practical difficulty in making the temperature distribution of the air uniform, as compared with the evaporator.

It should be noted that, in the heat exchanger 2 functioning as the condenser, a superheated gas region is generated, for example, as indicated by a dotted line SH in FIG. 3. The refrigerant in the gas state, which has a high flow velocity, flows into this superheated gas region SH through the flow inlet 211. Therefore, in order to adjust the refrigerant flow rate in the superheated gas region, for example, by providing a throttle or the like in the primary header tank 21, there is a concern that the pressure loss of the refrigerant in the gas state may increase. Thus, the inability to employ the means such as the throttle or the like in the primary header tank 21 is also a factor that makes it difficult to achieve a uniform temperature distribution of the air in the heat exchanger 2.

Next, functions and advantages of the heat exchanger 2 of the present embodiment will be described while comparing its structure with that of a heat exchanger 200 of a comparative example shown in FIGS. 6 to 8.

The heat exchanger 200 of the comparative example shown in FIGS. 6 and 7 has the same structure as the heat exchanger 2 shown in FIGS. 1 to 4, except that a plurality of communication holes 231 are uniformly arranged along the partition wall 23w of the primary turn tank 23, and a plurality of communication holes 241 are uniformly arranged along the partition wall 24w of the secondary turn tank 24. It should be noted that, in the heat exchanger 200 shown in FIGS. 6 and 7, elements identical to those of the heat exchanger 2 shown in FIGS. 1 to 4 are denoted by the same reference signs, and redundant descriptions are omitted.

In the heat exchanger 200 shown in FIGS. 6 and 7, the temperature distribution of the secondary core 25, which is disposed on the upstream side of the primary core 22 in the x-direction that is the flow direction of the air, changes according to the flow rate of the refrigerant.

Specifically, in a case where a flow rate of the refrigerant is high, when a length of the primary header tank 21 of FIG. 6 in the y-direction is increased, a pressure loss of the refrigerant in the primary header tank 21 increases. Therefore, since a large amount of the refrigerant flows through a near-side region 224 of the primary core 22, which is located near the flow inlet 211, as a shortcut flow, the flow rate of the refrigerant in the near-side region 224 increases, whereas the flow rate of the refrigerant in a far-side region 225, which is located far from the flow inlet 211, decreases. As a result, in the secondary core 25 as well, the flow rate of the refrigerant, which flows through the near-side region 254, increases, whereas the flow rate of the refrigerant, which flows through the far-side region 255, decreases. Therefore, since a subcooled liquid region SC10 is formed in the far-side region 255 of the secondary core 25, a temperature distribution is formed in the secondary core 25 such that the temperature in the far-side region 255 is excessively lower than the temperature in the near-side region 254 and the temperature in an intermediate region 256.

On the other hand, when the flow rate of the refrigerant is low, the pressure loss of the refrigerant in the primary header tank 21 becomes small. Therefore, in the primary core 22 shown in FIG. 7, the amount of the refrigerant, which flows as the shortcut flow through the near-side region 224 located adjacent to the flow inlet 211, decreases, and in the primary header tank 21, the amount of the refrigerant, which flows to the far-side that is far from the flow inlet 221, increases due to inertia. Therefore, in the primary header tank 21, the flow rate of the refrigerant flowing through an intermediate region 226, which is located between the near-side region 224 and the far-side region 225, becomes smaller compared to the near-side region 224 and the far-side region 225. As a result, in the secondary core 25 as well, the flow rate of the refrigerant, which flows through the near-side region 254, and the flow rate of the refrigerant, which flows through the far-side region 255, increase, whereas the flow rate of the refrigerant, which flows through the intermediate region 256, decreases. Accordingly, since a subcooled liquid region SC20 is formed in the intermediate region 256 of the secondary core 25, a temperature distribution is formed in the secondary core 25 such that the temperature in the intermediate region 256 is excessively lower than the temperature in the near-side region 254 and the temperature in the far-side region 255.

As described above, in the secondary core 25 of the heat exchanger 200, the temperature distribution, which corresponds to the flow rate of the refrigerant, is formed.

In the heat exchanger 200 of the comparative example shown in FIGS. 6 and 7, as illustrated in (A) and (B) of FIG. 8, a plurality of partition walls 243 are formed inside the secondary turn tank 24 to partition each of the plurality of communication holes 241, and a plurality of partition walls 233 are also formed inside the primary turn tank 23 to partition each of the plurality of communication holes 231. In such a case, the refrigerant is not pressure-equalized inside each of the turn tanks 23, 24. Accordingly, variations in the flow rate distribution of the refrigerant, as shown in FIGS. 6 and 7, are more likely to become pronounced, and as a result, the temperature distribution in the secondary core 25 may further deteriorate.

In this regard, in the heat exchanger 2 of the present embodiment, as shown in FIG. 3, the superheated gas refrigerant, which flows into the primary header tank 21, is distributed to the plurality of primary tubes 221 and flows toward the primary turn tank 23. As a result of this flow, a superheated gas region SH is formed in a region of the primary core 22 located adjacent to the primary header tank 21. As shown in (A) and (B) in FIG. 4, the entire interior of each of the turn tanks 23, 24 is continuous in the Y-direction, which is the longitudinal direction of the turn tank 23, 24. Accordingly, when the refrigerant flows into the primary turn tank 23 from the plurality of primary tubes 221, the pressure of the refrigerant in the primary turn tank 23 tends to become equalized inside the primary turn tank 23.

Further, when the refrigerant, whose pressure has been equalized inside the primary turn tank 23, flows into the secondary turn tank 24 through the communication holes, the flow rate of the refrigerant is controlled based on the arrangement of the communication holes in the primary turn tank 23 and the arrangement of the communication holes in the secondary turn tank 24 However, in order to maintain the pressure-equalized state of the refrigerant inside the secondary turn tank 24 at the time of controlling the flow rate of the refrigerant in the secondary turn tank 24, a change in the state of the refrigerant occurs due to a change in its density.

Specifically, the heat exchanger 2 of the present embodiment is configured such that the pressure loss in the respective secondary regions Tf, Tr shown in FIG. 3 becomes higher than the pressure loss in the primary region Tc.

The refrigerant, which flows into the primary turn tank 23, flows into the secondary turn tank 24 through the communication holes 23f1, 23f2, 23c1, 23c2, 23c3, 23c4, 23r1, 23r2 and the communication holes 24f1, 24f2, 24c1, 24c2, 24c3, 24c4, 24r1, 24r2. Since the pressure loss in the secondary regions Tf, Tr becomes higher than the pressure loss in the primary region Tc, the flow rate of the refrigerant, which flows through each of the secondary regions Tf, Tr, decreases compared to the flow rate of the refrigerant, which flows through the primary region Tc, and a subcooled liquid region SC is formed in each of the secondary regions Tf, Tr. A pair of subcooled liquid regions SC are formed on two opposite sides of the primary region Tc.

More specifically, in the heat exchanger 2 of the present embodiment, the primary region Tc, which corresponds to the communication holes 23c1, 23c2, 23c3, 23c4, 24c1, 24c2, 24c3, 24c4, the secondary outer region Tf1, which corresponds to the communication holes 23f1, 23f2, 24f1, 24f2, and the secondary outer region Tr1, which corresponds to the communication holes 23r1, 23r2, 24r1, 24r2, have smaller pressure losses than the secondary inner regions Tf2, Tr2, in which no communication holes are formed. Therefore, the flow rate of the refrigerant in the respective secondary inner regions Tf2, Tr2 becomes smaller than the flow rate of the refrigerant in each of the primary region Tc, the secondary outer region Tf1 and the secondary outer region Tr1. As a result, the subcooled liquid regions SC are formed in the portions of the secondary core 25 that respectively correspond to the secondary inner regions Tf2, Tr2. Thus, in the present embodiment, the communication holes are formed in the turn tanks 23, 24 as shown in FIG. 3 to control the flow rate of the refrigerant in the secondary core 25, thereby intentionally forming the subcooled liquid regions SC in the secondary core 25 as illustrated in FIG. 3. According to this configuration, even when the flow rate of the refrigerant is either high or low, the subcooled liquid regions SC tend to be formed in the portions of the secondary core 25 that respectively correspond to the secondary inner regions Tf2, Tr2. That is, variations in the flow rate of the refrigerant are less likely to cause deviation in the location of the subcooled liquid region shown in FIGS. 6 and 7. Furthermore, in the heat exchanger 2 of the present embodiment, local deterioration in the temperature distribution, as shown in FIGS. 6 and 7, is suppressed, and therefore the temperature distribution of the secondary core 25 in the Y-direction tends to become more uniform. As a result, the temperature of the air blown out from the heat exchanger 2 tends to become more uniform.

On the other hand, in such a heat exchanger 2, the refrigeration cycle is controlled so that the temperature of the refrigerant discharged from the flow outlet 261 reaches a target temperature. When such control is performed, the temperature distribution of the air blown out from, for example, the heat exchanger 200 of the comparative example shown in FIG. 7 tends to deteriorate. For example, in the heat exchanger 200 of the comparative example shown in FIG. 7, if the structures of the turn tanks 23, 24 are configured as shown in (A) and (B) of FIG. 8, the temperature of the intermediate region 256 may become excessively low compared to the temperatures of the near-side region 254 and the far-side region 255. Furthermore, the flows of the refrigerant that have passed through the near-side region 254, the far-side region 255 and the intermediate region 256, respectively, of the secondary core 25 are mixed in the secondary header tank 26, and the mixed flow of the refrigerant is discharged from the flow outlet 261. Accordingly, the temperature of the mixed flow of the refrigerant discharged from the flow outlet 261 becomes the average temperature of the flows of the refrigerant that have passed through the near-side region 254, the far-side region 255 and the intermediate region 256, respectively, of the secondary core 25. Therefore, even in a case where the target temperature of the refrigerant discharged from the flow outlet 261 is controlled to 40° C., the temperature of the intermediate region 256 in the secondary core 25 of the heat exchanger 200 of the comparative example shown in FIG. 7 may reach approximately 30° C. when the temperature of the near-side region 254 and the temperature of the far-side region 255 are approximately 50° C. In such a heat exchanger 200 of the comparative example, when the temperature of the refrigerant discharged from the flow outlet 261 is controlled to a target temperature, there is a concern that a temperature difference between the near-side region 254 and the far-side region 255, which have higher temperatures, and the intermediate region 256, which has a lower temperature, in the secondary core 25 may become more pronounced. Since the temperature distribution of the secondary core 25 is reflected in the temperature distribution of the air blown from the heat exchanger 200, the temperature distribution of the air tends to deteriorate in the heat exchanger 200 as a result. A similar issue may also occur in the heat exchanger 200 of the comparative example shown in FIG. 6.

In contrast, in the heat exchanger 2 of the present embodiment, as described above, the temperature distribution in the secondary core 25 tends to be more uniform compared to the heat exchanger 200 of the comparative examples shown in FIGS. 6 and 7. Accordingly, even when the temperature of the refrigerant discharged from the flow outlet 261 is controlled to the target temperature, it is unlikely that regions exhibiting a large temperature difference will occur in the secondary core 25. For example, in the heat exchanger 2 of the present embodiment, in the case where the target temperature of the refrigerant discharged from the flow outlet 261 is controlled to 40° C., the temperature of each of the subcooled liquid regions SC shown in FIG. 3 is approximately 38° C., while the temperatures of the other regions are approximately 40° C. Thus, in the heat exchanger 2 of the present embodiment, since the temperature distribution in the secondary core 25 tends to be more uniform, the temperature distribution of the air blown out from the heat exchanger 200 also tends to be more uniform as a result.

On the other hand, as indicated by a dot-dot-dash line in FIG. 3, in a case where the flow inlet 211 is formed at a center portion of the primary header tank 21, the flow inlet 211 is formed to extend in the z-direction from the center portion of the primary header tank 21. Similarly, in a case where the flow outlet 261 is formed at a center portion of the secondary header tank 26, the flow outlet 261 is formed to extend in the z-direction from the center portion of the secondary header tank 26. In such a structure, since pipes need to be connected to the flow inlet 211 and the flow outlet 261 in the z-direction, that is, in the vertical direction, the pipe routing may become more complicated.

In contrast, in the heat exchanger 2 of the present embodiment, as indicated by solid lines in FIG. 3, the flow inlet 211 is formed on a side surface (end surface) of the primary header tank 21, and the flow outlet 261 is formed on a side surface (end surface) of the secondary header tank 26. With such a configuration, since pipes can be connected to the flow inlet 211 and the flow outlet 261 in the y-direction, that is, in the horizontal direction, the pipe routing becomes easier. Further, by adopting a structure like that of the heat exchanger 2 of the present embodiment, the refrigerant can be made to flow in a downflow manner.

Furthermore, the heat exchanger 2 of the present embodiment has a one-pass structure with a 1-1 turn configuration, in which the refrigerant flows in a single direction through the primary core 22 and the secondary core 25. With the heat exchanger 2 having such a one-pass structure, a flow passage cross-sectional area can be increased compared to, for example, a heat exchanger in which the refrigerant flows back and forth multiple times in the primary core 22 and the secondary core 25, thereby reducing the pressure loss of the refrigerant. As another method that does not require consideration of the refrigerant pressure loss, a bypass branch, which bypasses the heat exchanger 2 during battery cooling, can be employed. However, such a method is difficult to adopt because it increases the cost.

FIG. 9 shows a modification of the heat exchanger 2. In the modification shown in FIG. 9, only the communication holes 23f1, 24f1 are formed in the secondary region Tf. In a primary turn tank 23V and a secondary turn tank 24V, the number of the communication holes in the secondary region Tf is smaller than the number of the communication holes in the secondary region Tr. The number of the communication holes in the secondary region Tr is smaller than the number of the communication holes in the primary region Tc.

Next, a heat exchanger 2A of a second embodiment will be described. FIG. 10 is a plan view corresponding to FIG. 3, showing the heat exchanger 2A. The heat exchanger 2A is a modified version of the heat exchanger 2, in which the primary turn tank 23 and the secondary turn tank 24 are replaced with a primary turn tank 23A and a secondary turn tank 24A.

The primary turn tank 23A includes a partition wall 23wA. The partition wall 23wA is a wall that contacts the secondary turn tank 24A. The partition wall 23wA has a plurality of communication holes 23f1A, 23f2A, 23f3A, 23f4A, 23c1A, 23c2A, 23r1A, 23r2A, 23r3A, 23r4A. The communication holes 23f1A, 23f2A, 23f3A, 23f4A, 23c1A, 23c2A, 23r1A, 23r2A, 23r3A, 23r4A are configured to conduct the refrigerant therethrough.

The communication holes 23f1A, 23f2A, 23f3A, 23f4A, 23r1A, 23r2A, 23r3A, 23r4A respectively have an identical circular shape. The communication holes 23c1A, 23c2A are openings, each of which has a larger cross-sectional area than the communication holes 23f1A, 23f2A, 23f3A, 23f4A, 23r1A, 23r2A, 23r3A, 23r4A, and the communication holes 23c1A, 23c2A respectively have, for example, an elliptical shape. It should be noted that all of the communication holes 23f1A, 23f2A, 23f3A, 23f4A, 23r1A, 23r2A, 23r3A, 23r4A are illustrated as having the identical circular shape for the sake of explanation, and the shape of the communication holes is not particularly limited. Various shapes may be adopted, including, for example, semicircular or rectangular shapes. Furthermore, each of the communication holes 23c1A, 23c2A only needs to be an opening having a larger cross-sectional area than the communication holes 23f1A, 23f2A, 23f3A, 23f4A, 23r1A, 23r2A, 23r3A, 23r4A. The elliptical shape of the communication holes 23c1A, 23c2A is merely an example, and various shapes may be adopted, including, for example, a semi-elliptical shape or a rectangular shape.

The communication holes 23f1A, 23f2A, 23f3A, 23f4A are included in the secondary region Tf. The communication holes 23c1A, 23c2A are included in the primary region Tc. The communication holes 23r1A, 23r2A, 23r3A, 23r4A are included in the secondary region Tr. A total opening cross-sectional area of the communication holes 23f1A, 23f2A, 23f3A, 23f4A formed in the secondary region Tf is smaller than a total opening cross-sectional area of the communication holes 23c1A, 23c2A formed in the primary region Tc. Similarly, a total opening cross-sectional area of the communication holes 23r1A, 23r2A, 23r3A, 23r4A formed in the secondary region Tr is smaller than the total opening cross-sectional area of the communication holes 23c1A, 23c2A formed in the primary region Tc. In terms of a ratio of opening cross-sectional areas of the communication holes 23f1A, 23f2A, 23f3A, 23f4A, 23c1A, 23c2A, 23r1A, 23r2A, 23r3A, 23r4A relative to a surface area of the partition wall 23wA, an opening ratio of the primary region Tc is larger than an opening ratio of the secondary region Tf and is also larger than an opening ratio of the secondary region Tr. A pressure loss in each of the pair of secondary regions Tf, Tr is higher than a pressure loss in the primary region Tc, and the primary region Tc is interposed between the pair of secondary regions Tf, Tr.

The secondary turn tank 24A includes a partition wall 24wA. The partition wall 24wA is a wall that contacts the primary turn tank 23A. The partition wall 24wA has a plurality of communication holes 24f1A, 24f2A, 24f3A, 24f4A, 24c1A, 24c2A, 24r1A, 24r2A, 24r3A, 24r4A. The communication holes 24f1A, 24f2A, 24f3A, 24f4A, 24c1A, 24c2A, 24r1A, 24r2A, 24r3A, 24r4A are configured to conduct the refrigerant therethrough. The communication holes 24f1A, 24f2A, 24f3A, 24f4A, 24r1A, 24r2A, 24r3A, 24r4A respectively have an identical circular shape. The communication holes 24c1A, 24c2A are openings, each of which has a larger cross-sectional area than the communication holes 24f1A, 24f2A, 24f3A, 24f4A, 24r1A, 24r2A, 24r3A, 24r4A, and have, for example, an elliptical shape.

The communication holes 24f1A, 24f2A, 24f3A, 24f4A are included in the secondary region Tf. The communication holes 24c1A, 24c2A are included in the primary region Tc. The communication holes 24r1A, 24r2A, 24r3A, 24r4A are included in the secondary region Tr. A total opening cross-sectional area of the communication holes 24f1A, 24f2A, 24f3A, 24f4A formed in the secondary region Tf is smaller than a total opening cross-sectional area of the communication holes 24c1A, 24c2A formed in the primary region Tc. Similarly, a total opening cross-sectional area of the communication holes 24r1A, 24r2A, 24r3A, 24r4A formed in the secondary region Tr is smaller than the total opening cross-sectional area of the communication holes 24c1A, 24c2A formed in the primary region Tc. In terms of a ratio of opening cross-sectional areas of the communication holes 24f1A, 24f2A, 24f3A, 24f4A, 24c1A, 24c2A, 24r1A, 24r2A, 24r3A, 24r4A relative to a surface area of the partition wall 24wA, an opening ratio of the primary region Tc is larger than an opening ratio of the secondary region Tf and is also larger than an opening ratio of the secondary region Tr. A pressure loss in each of the pair of secondary regions Tf, Tr is higher than a pressure loss in the primary region Tc, and the primary region Tc is interposed between the pair of secondary regions Tf, Tr.

In a state where the partition wall 23wA is in contact with the partition wall 24wA, the communication hole 23f1A in the secondary region Tf is in communication with the communication hole 24f1A. Similarly, the communication hole 23f2A is in communication with the communication hole 24f2A, the communication hole 23f3A is in communication with the communication hole 24f3A, and the communication hole 23f4A is in communication with the communication hole 24f4A. In the primary region Tc, the communication hole 23c1A is in communication with the communication hole 24c1A. Similarly, the communication hole 23c2A is in communication with the communication hole 24c2A. In the secondary region Tr, the communication hole 23r1A is in communication with the communication hole 24r1A, the communication hole 23r2A is in communication with the communication hole 24r2A, the communication hole 23r3A is in communication with the communication hole 24r3A, and the communication hole 23r4A is in communication with the communication hole 24r4A.

The superheated gas refrigerant, which flows into the primary header tank 21, is distributed to the plurality of primary tubes 221 and flows toward the primary turn tank 23A. As a result of this flow, a superheated gas region SH is formed in a region of the primary core 22 located adjacent to the primary header tank 21.

The refrigerant, which flows into the primary turn tank 23A, flows into the secondary turn tank 24A via the communication holes 23f1A, 23f2A, 23f3A, 23f4A, 23c1A, 23c2A, 23r1A, 23r2A, 23r3A, 23r4A and the communication holes 24f1A, 24f2A, 24f3A, 24f4A, 24c1A, 24c2A, 24r1A, 24r2A, 24r3A, 24r4A. Since the pressure loss in the secondary regions Tf, Tr becomes higher than the pressure loss in the primary region Tc, the flow rate of the refrigerant, which flows through each of the secondary regions Tf, Tr, decreases compared to the flow rate of the refrigerant, which flows through the primary region Tc, and a subcooled liquid region SC is formed in each of the secondary regions Tf, Tr. A pair of subcooled liquid regions SC are formed on two opposite sides of the primary region Tc.

Next, a heat exchanger 2B of a third embodiment will be described. FIG. 11 is a plan view corresponding to FIG. 3, showing the heat exchanger 2B. The heat exchanger 2B is a modified version of the heat exchanger 2, in which the primary turn tank 23 and the secondary turn tank 24 are replaced with a primary turn tank 23B and a secondary turn tank 24B.

The primary turn tank 23B includes a partition wall 23wB. The partition wall 23wB is a wall that contacts the secondary turn tank 24B. The partition wall 23wB has a plurality of communication holes 231 which extend through the partition wall 23wB. The number of the communication holes 231 is, for example, fourteen. The communication holes 231 are configured to conduct the refrigerant therethrough. All of the communication holes 231 have an identical circular shape. It should be noted that the communication holes 231 are all illustrated as having the identical circular shape merely for the sake of explanation, and the shape of the communication holes is not particularly limited. For example, the communication holes may take various shapes, including semicircular or rectangular shapes. In terms of a ratio of opening cross-sectional areas of the communication holes 231 relative to a surface area of the partition wall 23wB, an opening ratio of the primary region Tc is the same as an opening ratio of the secondary region Tf and is also the same as an opening ratio of the secondary region Tr.

The primary turn tank 23B includes a projection 232a and a projection 232b. The projection 232a is formed in the secondary region Tf. The projection 232b is formed in the secondary region Tr.

The secondary turn tank 24B includes a partition wall 24wB. The partition wall 24wB is a wall that contacts the primary turn tank 23B. The partition wall 24wB has a plurality of communication holes 241 which extend through the partition wall 24wB. The number of the communication holes 241 is, for example, fourteen. The communication holes 241 are configured to conduct the refrigerant therethrough. All of the communication holes 241 have an identical circular shape. In terms of a ratio of opening cross-sectional areas of the communication holes 241 relative to a surface area of the partition wall 24wB, an opening ratio of the primary region Tc is the same as an opening ratio of the secondary region Tf and is also the same as an opening ratio of the secondary region Tr.

The secondary turn tank 24B includes a projection 242a and a projection 242b. The projection 242a is formed in the secondary region Tf. The projection 242b is formed in the secondary region Tr.

Here, (A) of FIG. 12 is a cross-sectional view taken along line VIIIA-VIIIA of the secondary turn tank 24B in FIG. 11. Furthermore, (B) of FIG. 12 is a cross-sectional view taken along line VIIIB-VIIIB of the secondary turn tank 24B in FIG. 11. As shown in (A) and (B) of FIG. 12, the projection 242a locally reduces the internal volume of the secondary turn tank 24B. A pressure loss in each of the pair of secondary regions Tf, Tr is higher than a pressure loss in the primary region Tc, and the primary region Tc is interposed between the pair of secondary regions Tf, Tr.

The description is continued with reference again to FIG. 11. In a state where the partition wall 23wB is in contact with the partition wall 24wB, the communication holes 231 are in communication with the communication holes 241, respectively. The superheated gas refrigerant, which flows into the primary header tank 21, is distributed to the plurality of primary tubes 221 and flows toward the primary turn tank 23B. As a result of this flow, a superheated gas region SH is formed in a region of the primary core 22 located adjacent to the primary header tank 21.

The refrigerant, which flows into the primary turn tank 23B, flows into the secondary turn tank 24B via the communication holes 231 and the communication holes 241. Since a pressure loss in each of the secondary regions Tf, Tr, in which the projections 232a, 232b, 242a, 242b are formed, becomes higher than a pressure loss in the primary region Tc, the flow rate of the refrigerant, which flows through each of the secondary regions Tf, Tr, decreases compared to the flow rate of the refrigerant, which flows through the primary region Tc, and a subcooled liquid region SC is formed in each of the secondary regions Tf, Tr. A pair of subcooled liquid regions SC are formed on two opposite sides of the primary region Tc.

Next, a heat exchanger 2C of a fourth embodiment will be described. FIG. 13 is a plan view corresponding to FIG. 3, showing the heat exchanger 2C. The heat exchanger 2C is a modified version of the heat exchanger 2, in which the primary turn tank 23 and the secondary turn tank 24 are replaced with a primary turn tank 23C and a secondary turn tank 24C.

The primary turn tank 23C includes a flow restrictor 232C instead of the projections 232a, 232b of the primary turn tank 23B described with reference to FIG. 11. The secondary turn tank 24C includes a flow restrictor 242C instead of the projections 242a, 242b of the secondary turn tank 24B described with reference to FIG. 11.

Here, (A) of FIG. 14 is a cross-sectional view taken along line XA-XA of the secondary turn tank 24C in FIG. 13. Furthermore, (B) of FIG. 14 is a cross-sectional view taken along line XB-XB of the secondary turn tank 24C in FIG. 13. As shown in (A) of FIG. 14, the flow restrictor 242C is a member shaped in a flat plate form that is perpendicular to the Y-direction, and the flow restrictor 242C has a through-hole 242Ca at its center. As shown in (A) and (B) of FIG. 14, the flow restrictor 242C locally reduces the internal volume of the secondary turn tank 24B.

The description is continued with reference again to FIG. 13. The superheated gas refrigerant, which flows into the primary header tank 21, is distributed to the plurality of primary tubes 221 and flows toward the primary turn tank 23C. As a result of this flow, a superheated gas region SH is formed in a region of the primary core 22 located adjacent to the primary header tank 21.

The refrigerant, which flows into the primary turn tank 23C, flows into the secondary turn tank 24C via the communication holes 231 and the communication holes 241. Since the flow restrictors 232C, 242C are provided, the flow rate of the refrigerant, which flows through each of the secondary regions Tf, Tr, decreases relative to the flow rate of the refrigerant, which flows through the primary region Tc, and a subcooled liquid region SC is formed in each of the secondary regions Tf, Tr. A pair of subcooled liquid regions SC are formed on two opposite sides of the primary region Tc.

It is also possible that the secondary turn tank 24C of the heat exchanger 2C according to the fourth embodiment adopts a structure shown in FIG. 15. As shown in FIG. 15, a plurality of flow restrictors 244C, 245C, 246C, 247C are formed in the secondary turn tank 24C. The flow restrictor 244C is formed between the secondary outer region Tf1 and the secondary inner region Tf2. The flow restrictor 245C is formed between the secondary inner region Tf2 and the primary region Tc. The flow restrictor 246C is formed between the primary region Tc and the secondary inner region Tr2. The flow restrictor 247C is formed between the secondary inner region Tr2 and the secondary outer region Tr1. According to such a configuration, since flow resistance is generated in the longitudinal direction (Y-direction) in the secondary turn tank 24C, the entire interior of which is continuous in the Y-direction through the flow restrictors 244C, 245C, 246C, 247C, it is possible to reduce the flow velocity of the refrigerant in the secondary turn tank 24C. As a result, it is possible to enhance the effect of intentionally forming the subcooled liquid region SC having the reduced flow rate between the secondary outer region Tf1 and the primary region Tc, and the subcooled liquid region SC having the reduced flow rate between the secondary outer region Tr1 and the primary region Tc.

Next, a heat exchanger 2D of a fifth embodiment will be described. FIG. 16 is a plan view corresponding to FIG. 3, showing the heat exchanger 2D. The heat exchanger 2D is a modified version of the heat exchanger 2, in which the primary turn tank 23 and the secondary turn tank 24 are replaced with a primary turn tank 23D and a secondary turn tank 24D. The heat exchanger 2D is the modified version of the heat exchanger 2, in which the primary tubes 221 are replaced with a plurality of types of primary tubes 221Df, 221Dc, 221Dr. The heat exchanger 2D is the modified version of the heat exchanger 2, in which the secondary tubes 251 are replaced with a plurality of types of secondary tubes 251Df, 251Dc, 251Dr.

The primary turn tank 23D is obtained by removing the projections 232a, 232b from the primary turn tank 23B described with reference to FIG. 11. The secondary turn tank 24D is obtained by removing the projections 242a, 242b from the secondary turn tank 24B described with reference to FIG. 11.

The primary tubes 221Df and the secondary tubes 251Df are provided in the secondary region Tf. The primary tubes 221Dc and the secondary tubes 251Dc are provided in the primary region Tc. The primary tubes 221Dr and the secondary tubes 251Dr are provided in the secondary region Tr.

An internal flow passage of each of the primary tubes 221Df is narrower (i.e., with a smaller cross-sectional area) than an internal flow passage of each of the primary tubes 221Dc. An internal flow passage of each of the primary tubes 221Dr is narrower (i.e., with a smaller cross-sectional area) than the internal flow passage of each of the primary tubes 221Dc. An internal flow passage of each of the secondary tubes 251Df is narrower (i.e., with a smaller cross-sectional area) than an internal flow passage of each of the secondary tubes 251Dc. An internal flow passage of each of the secondary tubes 251Dr is narrower (i.e., with a smaller cross-sectional area) than the internal flow passage of each of the secondary tubes 251Dc.

FIG. 17 illustrates four examples of the internal flow passage configurations of the primary tubes 221Df, 221Dc, 221Dr and of the secondary tubes 251Df, 251Dc, 251Dr. Examples 1 and 2 are examples in which the tubes are formed by extrusion molding.

In Example 1, the internal flow passage of the primary tube 221Dc and the internal flow passage of the secondary tube 251Dc respectively have an identical shape. The internal flow passage of the primary tube 221Df and the internal flow passage of the secondary tube 251Df also respectively have an identical shape and are narrower (i.e., with a smaller cross-sectional area) than those of the primary tube 221Dc and the secondary tube 251Dc. The internal flow passage of the primary tube 221Dr and the internal flow passage of the secondary tube 251Dr also respectively have an identical shape, and are narrower (i.e., with a smaller cross-sectional area) than those of the primary tube 221Dc and the secondary tube 251Dc.

In Example 2 as well, the internal flow passage of the primary tube 221Dc and the internal flow passage of the secondary tube 251Dc respectively have an identical shape. In Example 2, among a plurality of sub-passages of the internal flow passage of each of the primary tube 221Df and the secondary tube 251Df, some sub-passages, which have the same shape as those of the primary tube 221Dc and the secondary tube 251Dc, are arranged at a center region, and the other sub-passages that are narrower than those in the center region are arranged on both sides of the center region. Also, among a plurality of sub-passages of the internal flow passage of each of the primary tube 221Dr and the secondary tube 251Dr, some sub-passages, which have the same shape as those of the primary tube 221Dc and the secondary tube 251Dc, are arranged at a center region, and the other sub-passages that are narrower than those in the center region are arranged on both sides of the center region.

Examples 3 and 4 are examples of tubes of an inner-fin type. In Example 3, a plurality of wavy fin segments of the inner fin of each of the primary tube 221Dc and the secondary tube 251Dc are arranged at an equal pitch. A plurality of wavy fin segments of the inner fin of each of the primary tube 221Df and the secondary tube 251Df are also arranged at an equal pitch, and this pitch is smaller than that of the primary tube 221Dc and the secondary tube 251Dc. The internal flow passages of the primary tube 221Df and the secondary tube 251Df are narrower (i.e., with a smaller cross-sectional area) than those of the primary tube 221Dc and the secondary tube 251Dc. The internal flow passages of the primary tube 221Dr and the secondary tube 251Dr are also narrower (i.e., with a smaller cross-sectional area) than those of the primary tube 221Dc and the secondary tube 251Dc.

In Example 4, a plurality of wavy fin segments of the inner fin of each of the primary tube 221Dc and the secondary tube 251Dc are arranged at an equal pitch. In Example 4, among a plurality of wavy fin segments of the inner fin of each of the primary tube 221Df and the secondary tube 251Df, some wavy fin segments having the same shape as those of the wavy fin segments of the primary tube 221Dc and the secondary tube 251Dc are arranged in a center region, and the other fin segments having a smaller pitch than the pitch in the center region are arranged on two opposite sides of the center region. The internal flow passages of the primary tube 221Df and the secondary tube 251Df are narrower (i.e., with a smaller cross-sectional area) than those of the primary tube 221Dc and the secondary tube 251Dc. The internal flow passages of the primary tube 221Dr and the secondary tube 251Dr are also narrower (i.e., with a smaller cross-sectional area) than those of the primary tube 221Dc and the secondary tube 251Dc.

The superheated gas refrigerant, which flows into the primary header tank 21, is distributed to the plurality of primary tubes 221Df, 221Dc, 221Dr and flows toward the primary turn tank 23D. As a result of this flow, a superheated gas region SH is formed in a region of the primary core 22 located adjacent to the primary header tank 21.

The refrigerant, which flows into the primary turn tank 23D, flows into the secondary turn tank 24D via the communication holes 231 and the communication holes 241. The refrigerant, which flows into the secondary turn tank 24D, is distributed to the secondary tubes 251Df, 251Dc, 251Dr and flows toward the secondary header tank 26.

The internal flow passage of each of the primary tubes 221Df, 221Dr is narrower than that of the primary tube 221Dc, and the internal flow passage of each of the secondary tubes 251Df, 251Dr is narrower than that of the secondary tube 251Dc. Therefore, the flow rate of the refrigerant, which flows through each of the secondary regions Tf, Tr, decreases relative to the flow rate of the refrigerant, which flows through the primary region Tc, and a subcooled liquid region SC is formed in each of the secondary regions Tf, Tr. A pair of subcooled liquid regions SC are formed on two opposite sides of the primary region Tc.

Next, a heat exchanger 2E of a sixth embodiment will be described. FIG. 18 is a plan view corresponding to FIG. 3, showing the heat exchanger 2E. The heat exchanger 2E is a modified version of the heat exchanger 2, in which the primary turn tank 23 and the secondary turn tank 24 are replaced with the primary turn tank 23D and the secondary turn tank 24D. Since the primary turn tank 23D and the secondary turn tank 24D are previously described with reference to FIG. 16, the description of the primary turn tank 23D and the secondary turn tank 24D is omitted.

The heat exchanger 2E differs from the heat exchanger 2 in that the intervals of the primary tubes 221 and the secondary tubes 251 are changed. The intervals of the primary tubes 221 and the secondary tubes 251, which are disposed in the primary region Tc, are reduced compared to the intervals of the primary tubes 221 and the secondary tubes 251, which are disposed in the secondary regions Tf, Tr. In other words, the intervals of the primary tubes 221 and the secondary tubes 251, which are disposed in the secondary regions Tf, Tr, are increased compared to the intervals of the primary tubes 221 and the secondary tubes 251, which are disposed in the primary region Tc.

The primary fins 222Ec and the secondary fins 252Ec, which are disposed in the primary region Tc, have smaller widths in the axial direction of the Y-axis than the primary fins 222Ef, 222Er and the secondary fins 252Ef, 252Er, which are disposed in the secondary regions Tf, Tr.

The superheated gas refrigerant, which flows into the primary header tank 21, is distributed to the plurality of primary tubes 221 and flows toward the primary turn tank 23D. As a result of this flow, a superheated gas region SH is formed in a region of the primary core 22 located adjacent to the primary header tank 21.

The refrigerant, which flows into the primary turn tank 23D, flows into the secondary turn tank 24D via the communication holes 231 and the communication holes 241. The refrigerant, which flows into the secondary turn tank 24D, is distributed to the secondary tubes 251 and flows toward the secondary header tank 26.

The intervals of the primary tubes 221, which are disposed in the secondary regions Tf, Tr, are increased compared to the intervals of the primary tubes 221, which are disposed in the primary region Tc, and the intervals of the secondary tubes 251, which are disposed in the secondary regions Tf, Tr, are increased compared to the intervals of the secondary tubes 251, which are disposed in the primary region Tc. Therefore, the flow rate of the refrigerant, which flows through each of the secondary regions Tf, Tr, decreases relative to the flow rate of the refrigerant, which flows through the primary region Tc, and a subcooled liquid region SC is formed in each of the secondary regions Tf, Tr. A pair of subcooled liquid regions SC are formed on two opposite sides of the primary region Tc.

Next, a heat exchanger 2F of a seventh embodiment will be described. FIG. 19 is a perspective view corresponding to FIG. 1, showing the heat exchanger 2F. The heat exchanger 2F differs from the heat exchanger 2 in that the primary turn tank 23 and the secondary turn tank 24 are replaced with a single turn tank 23F. The turn tank 23F includes a primary turn tank portion (a primary turn tank) 23Ff and a secondary turn tank portion (a secondary turn tank) 23Fs. The primary turn tank portion 23Ff corresponds to the primary turn tank 23. The secondary turn tank portion 23Fs corresponds to the secondary turn tank 24. The turn tank 23F is a unitary turn tank in which the primary turn tank portion 23Ff and the secondary turn tank portion 23Fs are integrated.

The turn tank 23F includes a plurality of communicating portions that connect between the primary turn tank portion 23Ff and the secondary turn tank portion 23Fs and are configured to conduct the refrigerant between the primary turn tank portion 23Ff and the secondary turn tank portion 23Fs. FIG. 20 is a perspective cross-sectional view showing a cross section where the communicating portions 231F are not provided.

As shown in FIG. 20, the turn tank 23F is formed by combining a first portion 23Fa and a second portion 23Fb together. The first portion 23Fa includes a coupling portion 23Fa1, a wall portion 23Fa2, a wall portion 23Fa3, a wall portion 23Fa4 and a wall portion 23Fa5.

The coupling portion 23Fa1 and the wall portions 23Fa2, 23Fa3 are respectively shaped in a flat plate form that extends in the y-direction and are arranged to have an x-y plane. The coupling portion 23Fa1 is held between the wall portion 23Fa2 and the wall portion 23Fa3 in the x-direction. The wall portion 23Fa2 and the wall portion 23Fa3 are displaced from the coupling portion 23Fa1 toward a minus side in the z-direction.

The wall portions 23Fa4, 23Fa5 are respectively shaped in a flat plate form that extends in the y-direction and are arranged to have a y-z plane. The wall portion 23Fa4 is joined to and is located on a side of the wall portion 23Fa2, which is opposite to the coupling portion 23Fa1. The wall portion 23Fa5 is joined to and is located on a side of the wall portion 23Fa3, which is opposite to the coupling portion 23Fa1.

The second portion 23Fb includes a coupling portion 23Fb1, a wall portion 23Fb2, a wall portion 23Fb3, a wall portion 23Fb4 and a wall portion 23Fb5.

The coupling portion 23Fb1 and the wall portions 23Fb2, 23Fb3 are respectively shaped in a flat plate form that extends in the y-direction and are arranged to have the x-y plane. The coupling portion 23Fb1 is held between the wall portion 23Fb2 and the wall portion 23Fb3 in the x-direction. The wall portion 23Fb2 and the wall portion 23Fb3 are displaced from the coupling portion 23Fb1 toward a positive side in the z-direction.

The wall portions 23Fb4, 23Fb5 are respectively shaped in a flat plate form that extends in the y-direction and are arranged to have the y-z plane. The wall portion 23Fb4 is joined to and is located on a side of the wall portion 23Fb2, which is opposite to the coupling portion 23Fb1. The wall portion 23Fb5 is joined to and is located on a side of the wall portion 23Fb3, which is opposite to the coupling portion 23Fb1.

When the first portion 23Fa and the second portion 23Fb are joined together such that the coupling portion 23Fa1 comes into contact with the coupling portion 23Fb1, the turn tank 23F is formed. The primary turn tank portion 23Ff is mainly formed by the wall portions 23Fa3, 23Fa5, 23Fb3, 23Fb5. The secondary turn tank portion 23Fs is mainly formed by the wall portions 23Fa2, 23Fa4, 23Fb2, 23Fb4. A plurality of communicating portions 231F are provided so as to connect and communicate between the primary turn tank portion 23Ff and the secondary turn tank portion 23Fs.

Here, (A) of FIG. 21 shows a cross-section taken along line XVIA-XVIA in FIG. 20, showing the communicating portion 231F. This cross-section is a cross-section taken along line XVIA-XVIA in a z-x plane in FIG. 20. Furthermore, (B) of FIG. 21 shows a XVIB-XVIB cross-section of the communicating portion 231F in FIG. 20. The XVIB-XVIB cross-section is a cross-section taken along line XVIB-XVIB in the y-z plane.

As shown in (A) and (B) of FIG. 21, each of the communicating portions 231F has an outer shell 231Fa. The outer shell 231Fa is shaped in a semicylindrical form. A communication hole 231Fb is formed between the outer shell 231Fa and the coupling portion 23Fa1. Each of the communication holes 231Fb is formed to communicate between the primary turn tank portion 23Ff and the secondary turn tank portion 23Fs.

The arrangement of the communication holes 231Fb may be the same as the arrangement of the communication holes described in the first to sixth embodiments. By the arrangement of the communication holes 231Fb, the primary region Tc and the secondary regions Tf, Tr can be formed in a manner similar to any one of the first to sixth embodiments.

The flow passage cross-sectional area of the communication hole 231Fb can be reduced by a method such as partially compressing the inside of the outer shell 231Fa. Examples of how to reduce the flow passage cross-sectional area will be described with reference to FIG. 22. In the example shown in (A) of FIG. 22, the outer shell 231Fa is compressed from above to form an outer shell 231FAa, which defines a communication hole 231FAb having a reduced cross-sectional area. In the example shown in (B) of FIG. 22, the outer shell 231Fa is further compressed from above and from both lateral sides to form an outer shell 231FBa, which defines a communication hole 231FBb having a further reduced cross-sectional area.

[Aspects] The following aspects 1 to 12 may be combined in any manner, as long as no technical inconsistency arises.

(Aspect 1)

According to aspect 1, there is provided a heat exchanger 2, 2A, 2B, 2C, 2D, 2E comprising:

• • a primary header tank 21 that is configured to receive a refrigerant in a superheated gas state from an upstream-side flow passage located on an upstream side of the heat exchanger in a flow direction of the refrigerant;
  • a plurality of primary tubes 221, 221Df, 221Dc, 221Dr that are configured to receive the refrigerant distributed from the primary header tank 21;
  • a primary turn tank 23, 23A, 23B, 23C, 23D, 23F that is configured to receive the refrigerant from the plurality of primary tubes 221, 221Df, 221Dc, 221D;
  • a secondary turn tank 24, 24A, 24B, 24C, 24D, 23F that is configured to receive the refrigerant from the primary turn tank 23, 23A, 23B, 23C, 23D, 23F;
  • a plurality of secondary tubes 251, 251Df, 251Dc, 251Dr that are configured to receive the refrigerant distributed from the secondary turn tank 24, 24A, 24B, 24C, 24D, 23F; and
  • a secondary header tank 26 that is configured to receive the refrigerant in a subcooled liquid state from the plurality of secondary tubes 251, 251Df, 251Dc, 251D and then output the refrigerant into a downstream-side flow passage located on a downstream side of the heat exchanger in the flow direction of the refrigerant, wherein:
  • an internal flow path, which extends from the plurality of primary tubes 221, 221Df, 221Dc, 221D to the plurality of secondary tubes 251, 251Df, 251Dc, 251Dr via the primary turn tank 23, 23A, 23B, 23C, 23D, 23F and the secondary turn tank 24, 24A, 24B, 24C, 24D, 23F, has a primary region Tc and at least one secondary region Tf, Tr that are arranged one after another in a stacking direction y, in which the plurality of primary tubes 221, 221Df, 221Dc, 221Dr are stacked and the plurality of secondary tubes 251, 251Df, 251Dc, 251Dr are stacked, wherein a pressure loss of the primary region Tc and a pressure loss of the at least one secondary region Tf, Tr are different from each other when a flow rate of the refrigerant in the primary region Tc is the same as a flow rate of the refrigerant in the at least one secondary region Tf, Tr.

According to aspect 1, since the primary region Tc and the at least one secondary region Tf, Tr, which are different in pressure loss when the refrigerant flows at the same flow rate in the primary region Tc and the at least one secondary region Tf, Tr, are provided, it is possible to adjust the flow rate of the refrigerant flowing through the primary region Tc and the flow rate of the refrigerant flowing through the at least one secondary region Tf, Tr. Since the primary region Tc and the at least one secondary region Tf, Tr are arranged one after another in the axial direction of the y-axis, i.e., the stacking direction, in which the plurality of primary tubes 221, 221Df, 221Dc, 221Dr are stacked and the plurality of secondary tubes 251, 251Df, 251Dc, 251Dr are stacked, it is possible to adjust the flow rate of the refrigerant in a direction that intersects a direction in which air flows. For example, by suppressing the flow rate of the refrigerant to promote heat exchange of the refrigerant, it is possible to form a subcooled liquid region at a desired location, thereby maintaining a favorable temperature distribution. For example, even in a case where the heat exchanger 2, 2A, 2B, 2C, 2D, 2E is used for heating a vehicle interior and the air flow rates differ between the left and right sides in the y-axis direction, the subcooled liquid region can be formed on each side, thereby maintaining the favorable temperature distribution between the left and right sides.

(Aspect 2)

According to aspect 2, there is provided the heat exchanger 2, 2A, 2B, 2C, 2D, 2E according to aspect 1, wherein:

• • the pressure loss in the at least one secondary region Tf, Tr is higher than the pressure loss in the primary region Tc; and
  • the at least one secondary region Tf, Tr includes a pair of secondary regions Tf, Tr between which the primary region Tc is interposed.

According to aspect 2, the flow rate of the refrigerant, which flows through each of the secondary regions Tf, Tr, decreases relative to the flow rate of the refrigerant, which flows through the primary region Tc, and subcooled liquid regions SC are formed in the secondary regions Tf, Tr, respectively. Since the subcooled liquid regions SC are formed in correspondence with the secondary regions Tf, Tr, the pair of subcooled liquid regions Sc are formed on the two opposite sides, respectively, of the primary region Tc. For example, in a case where the secondary region Tf is located adjacent to a region where the refrigerant flows into the primary header tank 21, even when the flow rate of the refrigerant, which flows into the primary header tank 21, is low, it is possible to suppress an excessive flow of the refrigerant toward the secondary region Tf which flows as the shortcut flow. For example, in a case where the secondary region Tr is formed on the side opposite to the side where the refrigerant flows into the primary header tank 21, even when the flow rate of the refrigerant, which flows into the primary header tank 21, is high, it is possible to suppress an excessive flow of the refrigerant toward the secondary region Tr.

In a case where the flow velocity of the refrigerant, which flows in the primary header tank 21, is low, and the pressure loss is small, and the air flow is evenly applied to the plurality of primary tubes 221, 221Df, 221Dc, 221Dr and the plurality of secondary tubes 251, 251Df, 251Dc, 251Dr, the refrigerant is distributed uniformly to the respective tubes. However, in a case where a duct is provided on an upstream side of the heat exchanger 2, 2A, 2B, 2C, 2D, 2E, and the duct has a rectangular shape, the air tends to flow more strongly near the center of the heat exchanger 2, 2A, 2B, 2C, 2D, 2E. Therefore, the amount of heat exchange in the primary region Tc becomes larger than the amount of heat exchange in each of the secondary regions Tf, Tr, resulting in a subcooled state in the primary region Tc. When the primary region Tc is in the subcooled state, a pressure corresponding to ρgh is required to lift the heavier liquid in the primary region Tc. To ensure this, a certain pressure loss is needed. In view of this, the pressure loss in each of the secondary regions Tf, Tr is increased to allow the refrigerant to flow into the primary region Tc.

In a case where the flow velocity of the refrigerant, which flows in the primary header tank 21, is high, resulting in a large pressure loss, the flow rate of the refrigerant, which flows into the secondary region Tr, decreases. In view of this, it is necessary to increase the pressure loss in the primary region Tc and the secondary region Tf, excluding the secondary region Tr. As a result, compared to a low flow rate state, it is necessary to increase the pressure loss in the regions other than the primary region Tc, and it is also necessary to increase the pressure loss in the primary region Tc and the secondary region Tf due to the high flow rate. In order to equalize the temperature distribution in the longitudinal direction (left-right direction) of the primary header tank 21, the pressure loss in each of the secondary regions Tf, Tr, which are other than the primary region Tc, is similarly increased to provide the pair of supercooled liquid regions.

It should be noted that the configuration, in which the pair of secondary regions Tf, Tr are provided on the two opposite sides of the primary region Tc, is merely one example, and the secondary regions Tf, Tr may be provided in any manner as long as the secondary regions Tf, Tr are arranged alongside the primary region Tc in the axial direction of the Y-axis.

(Aspect 3)

According to aspect 3, there is provided the heat exchanger 2, 2A, 2B according to aspect 1 or 2, wherein the primary region Tc and the at least one secondary region Tf, Tr are formed in at least one of the primary turn tank 23, 23A, 23B or the secondary turn tank 24, 24A, 24B.

According to aspect 3, since the primary region Tc and the at least one secondary region Tf, Tr are provided in the at least one of the primary turn tank 23, 23A, 23B or the secondary turn tank 24, 24A, 24B, the primary region Tc and the at least one secondary region Tf, Tr can be formed easily without requiring any special tubes.

(Aspect 4)

According to aspect 4, there is provided the heat exchanger 2, 2A according to aspect 3, wherein:

• • a partition wall 23w, 23wA, 24w, 24wA is placed between the primary turn tank 23, 23A and the secondary turn tank 24, 24A; and
  • the primary region Tc and the at least one secondary region Tf, Tr are formed in the partition wall 23w, 23wA, 24w, 24wA.

According to aspect 4, since the primary region Tc and the at least one secondary region Tf, Tr are formed in the partition wall 23w, 23wA, 24w, 24wA, the primary region Tc and the at least one secondary region Tf, Tr can be easily formed by processing only the partition wall 23w, 23wA, 24w, 24wA.

(Aspect 5)

According to aspect 5, there is provided the heat exchanger 2 according to aspect 4, wherein:

• • the partition wall 23w, 24w has a plurality of communication holes which extend through the partition wall 23w, 24w and are configured to conduct the refrigerant;
  • among the plurality of communication holes, one or more communication holes 23f1, 23f2, 24f1, 24f2 are formed in the at least one secondary region Tf, and two or more communication holes 23c1, 23c2, 23c3, 23c4, 24c1, 24c2, 24c3, 24c4 are formed in the primary region Tc; and
  • a number of the one or more communication holes 23f1, 23f2, 24f1, 24f2 formed in the at least one secondary region Tf is smaller than a number of the two or more communication holes 23c1, 23c2, 23c3, 23c4, 24c1, 24c2, 24c3, 24c4 formed in the primary region Tc. Similarly, the number of the communication holes 23r1, 23r2, 24r1, 24r2 formed in the secondary region Tr is smaller than the number of the communication holes 23c1, 23c2, 23c3, 23c4, 24c1, 24c2, 24c3, 24c4 formed in the primary region Tc.

According to aspect 5, the primary region Tc and the at least one secondary region Tf, Tr can be easily formed by setting different numbers of communication holes in the primary region Tc and in the at least one secondary region Tf, Tr in the partition wall 23w, 24w. Furthermore, by adjusting the numbers of the communication holes formed in the partition wall 23w, 24w, a difference in the flow rate of the refrigerant can also be adjusted, so that the formation position and the formation manner of the at least one secondary region Tf, Tr relative to the primary region Tc can be more easily adjusted.

(Aspect 6)

According to aspect 6, there is provided the heat exchanger 2 according to aspect 5, wherein:

• • the at least one secondary region Tf, Tr includes a pair of secondary regions Tf, Tr; and
  • assuming that Nall is a number of virtual communication holes that would be present when the virtual communication holes, each having an identical configuration as each of the plurality of communication holes, were uniformly arranged in the primary region Tc and the pair of secondary regions Tf, Tr, and that Nsc is a virtual number of missing communication holes that would be present when the virtual communication holes were uniformly arranged in the primary region Tc and the pair of secondary regions Tf, Tr, provided that the missing communication holes were counted between one of the plurality of communication holes located at an outer end of the primary region Tc and another one of the plurality of communication holes located at an inner end of one of the pair of secondary regions Tf, Tr, a ratio Nsc/Nall is equal to or larger than 0.12; and
  • a total opening cross-sectional area of the plurality of communication holes actually arranged in the primary region Tc and the pair of secondary regions Tf, Tr is equal to or larger than 21.18 mm².

In aspect 6, the case where the virtual communication holes are uniformly arranged in the primary region Tc and the pair of secondary regions Tf, Tr refers to, for example, a state similar to the arrangement of the communication holes 241 illustrated in FIG. 16. On the other hand, a state in which the communication holes are actually arranged in the primary region Tc and the pair of secondary regions Tf, Tr, and which also satisfies the condition of aspect 5, refers to, for example, a state similar to the state illustrated in FIG. 3. In the case, which is similar to the case exemplified in FIG. 16, Nall is 14. In the case similar to the case exemplified in FIG. 3, the one of the plurality of communication holes located at the outer end of the primary region Tc is the communication hole 23c1, 24c1 or the communication hole 23c4, 24c4. The another one of the plurality of communication holes located at the inner end of the one of the pair of secondary regions Tf, Tr is the communication hole 23f2, 24f2 or the communication hole 23r1, 24r1. If the communication holes were uniformly arranged between the communication hole 23c1 and the communication hole 23f2, the number of these communication holes would be two. Similarly, if the communication holes were uniformly arranged between the communication hole 23c4 and the communication hole 23r1, the number of these communication holes would be two. Similarly, if the communication holes were uniformly arranged between the communication hole 24c1 and the communication hole 24f2, the number of these communication holes would be two. Similarly, if the communication holes were uniformly arranged between the communication hole 24c4 and the communication hole 24r1, the number of these communication holes would be two. Therefore, in these examples, Nsc is 2. Therefore, the ratio Nsc/Nall=2/14=0.14, which satisfies the condition of Nsc/Nall≥0.12.

The outer end of the primary region Tc refers, in other words, to an end portion of the primary region Tc on the secondary region Tf side or an end portion of the primary region Tc on the secondary region Tr side. The inner end of the secondary region Tf refers, in other words, to an end portion of the secondary region Tf on the primary region Tc side, or an end portion of the secondary region Tr on the primary region Tc side.

FIGS. 23 and 24 are graphs respectively showing results of experiments conducted by the inventors of the present application. A graph shown in FIG. 23 illustrates a relationship between Nsc/Nall, which is plotted on the horizontal axis, and a left-right temperature difference ΔT of the air blown out from the heat exchanger 2, which is plotted on the vertical axis. Here, it is assumed that the direction indicated by arrow Y in FIG. 3 is defined as the right direction, and the opposite direction is the left direction. With this assumption, the left-right temperature difference ΔT of the air blown out from the heat exchanger 2 is defined as a difference between the temperature of the air blown out after exchanging heat with a portion of the heat exchanger 2 located on the left side of the center portion in the Y-axis direction, and the temperature of the air blown out after exchanging heat with a portion of the heat exchanger 2 located on the right side of the center portion in the Y-axis direction. In the graph shown in FIG. 23, a solid line L20 indicates a case where the height of the cores 22, 25 in the Z-direction is small, and a dot-dash line L21 indicates a case where the height of the cores 22, 25 in the Z-direction is large. As shown in the graph of FIG. 23, when the ratio Nsc/Nall is equal to or larger than 0.12, the left-right temperature difference ΔT of the heat exchanger 2 becomes equal to or less than a threshold value ΔTa. The threshold value ΔTa indicates an allowable value of a difference between the temperature of air blown toward a driver's seat side and the temperature of air blown toward a passenger's seat side, among air blown into a vehicle cabin through the heat exchanger 2. As shown in the graph of FIG. 23, when the ratio Nsc/Nall becomes equal to or larger than 0.12, the left-right temperature difference ΔT of the heat exchanger 2 rapidly decreases. In other words, the left-right temperature difference ΔT of the heat exchanger 2 is reduced, meaning that the thermal uniformity is improved.

The graph shown in FIG. 24 illustrates a relationship between a total opening cross-sectional area AS of the communication holes 241 actually provided in the primary region Tc and the secondary regions Tf, Tr, plotted on the horizontal axis, and the pressure loss PL of the refrigerant, plotted on the vertical axis. As shown in the graph of FIG. 24, when the total opening cross-sectional area AS of the communication holes 241 is equal to or larger than 21.18 mm², the pressure loss PL of the refrigerant can be made smaller than the threshold value PLa. The threshold value PLa is, for example, an allowable value of the pressure loss of the refrigerant that enables sufficient cooling performance in a case where a battery of an electric vehicle is cooled using a refrigeration cycle employing the heat exchanger 2 of the present embodiment.

(Aspect 7)

According to aspect 7, there is provided the heat exchanger 2A according to aspect 4, wherein:

• • the partition wall 23wA, 24wA has a plurality of communication holes which extend through the partition wall 23wA, 24wA and are configured to conduct the refrigerant;
  • among the plurality of communication holes, one or more communication holes 23f1A, 23f2A, 23f3A, 23f4A are formed in the at least one secondary region Tf, and one or more communication holes 23c1A, 23c2A are formed in the primary region Tc; and
  • a total cross-sectional area of the one or more communication holes 23f1A, 23f2A, 23f3A, 23f4A formed in the at least one secondary region Tf is smaller than a total cross-sectional area of the one or more communication holes 23c1A, 23c2A formed in the primary region Tc. Similarly, a total cross-sectional area of the one or more communication holes 23r1A, 23r2A, 23r3A, 23r4A formed in the secondary region Tr is smaller than the total cross-sectional area of the one or more communication holes 23c1A, 23c2A formed in the primary region Tc.

According to aspect 7, by making the total cross-sectional area of the communication holes provided in the partition wall 23wA, 24wA between the primary region Tc and the at least one secondary region Tf, Tr different from each other, the primary region Tc and the at least one secondary region Tf, Tr can be easily defined. Furthermore, by adjusting the total cross-sectional areas of the communication holes formed in the partition wall 23w, 24w, a difference in the flow rate of the refrigerant can also be adjusted, so that the formation position and the formation manner of the at least one secondary region Tf, Tr relative to the primary region Tc can be more easily adjusted. The total cross-sectional area of the communication holes refers to the sum of the opening cross-sectional areas of the communication holes formed in the region.

(Aspect 8)

According to aspect 8, there is provided the heat exchanger 2B, 2C according to aspect 3, wherein an internal cross-sectional area of the at least one of the primary turn tank 23B, 23C or the secondary turn tank 24B, 24C is formed to vary at least in part along the stacking direction (the axial direction of the Y-axis), and thereby the primary region Tc and the at least one secondary region Tf, Tr are formed accordingly.

According to aspect 8, by varying the internal cross-sectional area of the at least one of the primary turn tanks 23B, 23C or the secondary turn tank 24B, 24C in the axial direction of the Y-axis, a difference in pressure loss is created, thereby allowing the primary region Tc and the at least one secondary region Tf, Tr to be easily formed.

(Aspect 9)

According to aspect 9, there is provided the heat exchanger 2C according to aspect 8, wherein the internal cross-sectional area of the at least one of the primary turn tank 23C or the secondary turn tank 24C is varied by providing a flow restrictor 232C, 242C inside the at least one of the primary turn tank 23C or the secondary turn tank 24C.

(Aspect 10)

According to aspect 10, there is provided the heat exchanger according to aspect 8, wherein the internal cross-sectional area of the at least one of the primary turn tank 23B or the secondary turn tank 24B is varied by varying an inner wall shape of the at least one of the primary turn tank 23B or the secondary turn tank 24B. As one example, the inner wall shape can be varied by providing the projection 232a, 242a described with reference to FIGS. 11 and 12.

(Aspect 11)

According to aspect 11, there is provided the heat exchanger 2D, 2E according to aspect 1 or 2, wherein the primary region Tc and the at least one secondary region Tf, Tr are formed in the plurality of primary tubes and/or the plurality of secondary tubes.

(Aspect 12)

According to aspect 12, there is provided the heat exchanger according to aspect 11, wherein among the plurality of primary tubes and the plurality of secondary tubes, an internal flow passage of each of the primary tubes 221Df, 221Dr and/or an internal flow passage of each of the secondary tubes 251Df, 251Dr arranged in the at least one secondary region Tf, Tr is narrower than an internal flow passage of each of the primary tubes 221Dc and/or an internal flow passage of each of the secondary tubes (251Dc arranged in the primary region Tc.

According to aspect 12, a difference in pressure loss is formed by varying the internal flow passages of the tubes, so the primary region Tc and the at least one secondary region Tf, Tr can be formed by a simple means such as changing the tubes.

(Aspect 13)

According to aspect 13, there is provided the heat exchanger according to aspect 11, wherein among the plurality of primary tubes and the plurality of secondary tubes, a number of the primary tubes 221 and/or the secondary tubes 251 arranged in the at least one secondary region Tf, Tr is smaller than a number of the primary tubes 221 and/or the secondary tubes 251 arranged in the primary region Tc.

According to aspect 13, the primary region Tc and the at least one secondary region Tf, Tr can be formed by a simple means such as varying the number of tubes, while using ordinary tubes and making no modification to the turn tanks.

The present embodiment has been described above with reference to the specific examples. However, the present disclosure is not limited to the above specific examples. Appropriate design changes made by those skilled in the art to the above specific examples are also included in the scope of the present disclosure as long as they have the features of the present disclosure. Each element included in the specific examples described above, and its arrangement, conditions, shape, etc., are not limited to those illustrated and can be changed as appropriate. As long as there is no technical contradiction, the combination of the elements included in the specific examples described above can be changed as appropriate.