HEAT EXCHANGE SYSTEM AND HEAT EXCHANGE METHOD

Description

FOREIGN PRIORITY

This application claims the benefit of Chinese Patent Application No. 202410114501.6, filed Jan. 26, 2024, and all the benefits accruing therefrom under 35 U.S.C. § 119, the contents of which in its entirety are herein incorporated by reference.

TECHNICAL FIELD

The disclosure relates to the technical field of refrigeration, in particular to a heat exchange system and a heat exchange method for the heat exchange system.

BACKGROUND

In a refrigeration system, a refrigerant flows through a compressor, is compressed in the compressor to be in a high-temperature and high-pressure condition, and is then discharged out of the compressor at a high velocity and a high temperature, and under the action of a high temperature, lubricating oil in the compressor will be discharged in the form of oil vapor or particles mixed with a refrigerant gas. In the prior art, an oil separator was arranged on the outlet side of the compressor to separate lubricating oil from the refrigerant gas.

However, in the prior art, when the discharge superheat of the refrigerant is less than 4-5 K, the performance of the oil separator will become extremely poor, the separation effect will be affected, and a large quantity of the refrigerant will be dissolved in lubricating oil, reducing the viscosity of the lubricating oil. Moreover, in some refrigeration systems, the temperature of an outlet of the oil separator may reach 90° C. or over. Such a high temperature will reduce the viscosity of lubricating oil returning into the compressor, possibly aggravating abrasion of components in the compressor, shortening the service life of the compressor, and even causing damage to components in the compressor such as the bearing.

SUMMARY OF THE INVENTION

In view of the above problems, the disclosure provides a heat exchange system and a heat exchange method. The heat exchange system can increase suction superheat of a refrigerant and decrease the temperature of lubricating oil, thus improving the cooling effect on a bearing, improving the viscosity and lubrication performance of the lubricating oil, improving the performance of a compressor, and prolonging the service life of the compressor.

In one aspect, the technical solution of the disclosure provides a heat exchange system, comprising a compressor, an evaporator, a heat exchanger, an inlet line, a first regulating device and an outlet line. A refrigerant circulates in the evaporator, a heat exchange line is arranged in the heat exchanger, the inlet line is connected to the evaporator and the heat exchange line, the first regulating device is arranged on the inlet line and used for pumping the refrigerant from the evaporator into the heat exchange line, and the outlet line is connected to a suction inlet of the compressor and the heat exchange line.

Optionally, in the technical solution of the disclosure, the heat exchange system further comprises a second regulating device arranged on the outlet line.

Optionally, in the technical solution of the disclosure, the heat exchange line comprises a primary-side line and a secondary-side line, the heat exchange system further comprises an oil separator, and an oil and refrigerant mixture from the oil separator flows through the primary-side line; and the refrigerant from the inlet line flows through the secondary-side line.

Optionally, in the technical solution of the disclosure, a temperature difference between the refrigerant in the inlet line and the refrigerant in the outlet line is within 20-40° C., and a temperature difference of the oil and refrigerant mixture before and after flowing through the heat exchange line is within 20-50° C.

Optionally, in the technical solution of the disclosure, the first regulating device and/or the second regulating device is configured as an air pump or a flow control valve.

In another aspect, the technical solution of the disclosure further provides a heat exchange method applied to the heat exchange system. The heat exchange method comprises: a step of heat exchange: pumping the refrigerant from the inlet line into the heat exchange line to exchange heat with the oil and refrigerant mixture in the heat exchange line; and a step of discharging: discharging the refrigerant subjected to heat exchange to the suction inlet of the compressor by means of the outlet line.

Optionally, in the technical solution of the disclosure, the heat exchange method further comprises a step of regulation: regulating a pressure of the refrigerant or a flow rate of the refrigerant in the inlet line and/or in the outlet line respectively by means of the first regulating device arranged on the inlet line and/or the second regulating device arranged on the outlet line.

Optionally, in the technical solution of the disclosure, a temperature of the refrigerant in the outlet line is increased by 20° C.-40° C., compared with a temperature of the refrigerant in the inlet line.

Optionally, in the technical solution of the disclosure, a temperature difference of the oil and refrigerant mixture before and after flowing through the heat exchange line is within 20-50° C.

According to the technical solution of the disclosure, part of the refrigerant in the evaporator flows through the secondary-side line of the heat exchange line in the heat exchanger to be heated by heat exchange, and at the suction inlet of the compressor (the outlet of the evaporator), the refrigerator heated by heat exchange is mixed with the refrigerant discharged from the outlet of the evaporator, such that the temperature of the refrigerant flowing into the suction inlet of the compressor is increased, and the difference between the temperature of the refrigerant flowing into the suction inlet of the compressor and the evaporating temperature of the refrigerant is increased, that is, the superheat of the refrigerant is increased, thus avoiding liquid slugging caused by part of the refrigerant entering the compressor in a liquid state in case of insufficient superheat, improving the discharge superheat of the compressor, and improving the oil separation efficiency of the oil separator.

In addition, the high-temperature and high-pressure oil and refrigerant mixture from the oil-gas separator flows through the primary-side line of the heat exchange line in the heat exchanger and exchanges heat with the refrigerant in the secondary-side line of the heat exchange line in the heat exchanger, such that the temperature of lubricating oil is decreased. The viscosity of the lubricating oil is increased, thus decreasing the temperature of a bearing, effectively improving the lubricating effect, reducing abrasion of the compressor in operation, and prolonging the service life of the compressor.

The technical solution of the disclosure fulfills the above technical effects by means of a simple design only by arranging the heat exchanger and corresponding lines, without adding special equipment.

DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a schematic diagram of a refrigeration system in the prior art.

FIG. 2 is a schematic diagram of a refrigeration system according to one or more embodiments of the disclosure.

FIG. 3 is a schematic diagram of a heat exchange system according to one or more embodiments of the disclosure.

FIG. 4 is a flow diagram of a heat exchange method according to one or more embodiments of the disclosure.

FIG. 5 is a schematic diagram of a heat exchanger according to one or more embodiments of the disclosure.

LIST OF REFERENCE NUMERALS

• • 100, refrigeration system; 101, compressor; 102, condenser; 103, expansion valve; 104, evaporator; 105, oil separator; 200, refrigeration system; 201, compressor; 202, condenser; 203, expansion valve; 204, evaporator; 205, oil separator; 1, heat exchange system; 2, heat exchanger; 3, inlet line; 4, first regulating device; 5, outlet line; 6, second regulating device; 7, primary-side of heat exchanger; 8, secondary-side of heat exchanger; 9, refrigerant inlet of heat exchanger; 10, refrigerant inlet of heat exchanger; 11, oil inlet of heat exchanger; 12, oil outlet of heat exchanger; A1, suction inlet of compressor; A2, outlet of compressor; A3, lubricating oil inlet of compressor; B1, inlet of evaporator; B2, outlet of evaporator; B3, heat-exchange outlet of evaporator; C1, inlet of oil separator; C2, refrigerant outlet of oil separator; C3, mixture outlet of oil separator.

DETAILED DESCRIPTION

First, it should be noted that the components, operating principle, features, and advantages of a refrigeration system according to the disclosure will be described by way of examples. However, it should be understood that all descriptions are provided merely for illustration and thus should not be construed as limitations of the disclosure.

In addition, for any technical features described or implied in the embodiments mentioned here or any technical features shown or implied in the drawings, the application allows for any combination or deletion of these technical features (or their equivalents) without any technical obstacles, so as to obtain more other embodiments, that are not directly mentioned here, of the disclosure.

FIG. 1 is a schematic diagram of a refrigeration system in the prior art.

As shown in FIG. 1, a refrigeration system 100 comprises a compressor 101, a condenser 102, an expansion valve 103 and an evaporator 104 which are connected in sequence.

In a refrigeration/heating cycle of the refrigeration system 100, first, a step of compression is performed: the compressor 101 sucks a refrigerant gas from the evaporator 104 and compresses the refrigerant gas to increase the pressure of the refrigerant gas so as to obtain a high-temperature and high-pressure refrigerant gas.

Then, a step of condensation is performed: the high-temperature and high-pressure refrigerant gas discharged from the compressor 101 exchanges heat with cooling water in the condenser 102, such that temperature of the cooling water in the condenser 102 is increased, and the refrigerant gas is condensed into a refrigerant liquid.

Next, a step of expansion is performed: the high-temperature and high-pressure refrigerant liquid from the condenser 102 flows through the expansion valve 103 for throttling expansion, such that the pressure and temperature of the refrigerant liquid are decreased to obtain a low-temperature and low-pressure refrigerant liquid.

Finally, a step of evaporation is performed: the low-temperature and low-pressure refrigerant liquid absorb heat from a heat exchange medium in the evaporator 104 to be evaporated into a gas, and the temperature of the heat exchange medium in the evaporator 104 is decreased at the same time. The refrigerant gas discharged from an outlet of the evaporator 104 is sucked again into the compressor 101 to be compressed, and the step of compression, the step of condensation, the step of throttling and the step of evaporation cycle are repeated.

In the evaporation process, when the gas evaporated from the refrigerant liquid is sucked again into compressor 101, the suction temperature of the refrigerant should be slightly higher than the evaporating temperature. That is, certain suction superheat of the refrigerant should be maintained to ensure that the refrigerant sucked into the compressor 101 can be in a gaseous state to prevent liquid slugging, which may otherwise affect normal operation of the compressor 101.

In addition, the compressor 101 in the refrigeration system 100 is configured as a screw compressor. When the screw compressor operates, lubricating oil needs to be sprayed between a screw and other components of the screw compressor, and an oil film is formed between rotors by the lubricating oil to fulfill sealing, lubricating and cooling effects. Referring to FIG. 1, the oil separator 105 is arranged on an outlet side of compressor 101 and used for separating lubricating oil from the refrigerant gas. The refrigerant gas separated out by the oil separator 105 flows to the condenser 102, the expansion valve 103 and the evaporator 104 to continue the refrigeration cycle of the refrigeration system 100. The lubricating oil separated out by the oil separator 105 returns into the compressor 101 to be used for lubrication. In FIG. 1, the flow path of the refrigerant is indicated by the solid line, and the flow path of an oil and refrigerant mixture/the lubricating oil is indicated by the dashed line.

However, in the above technical solution, the lubricating oil separated out by the oil separator 105 has a high temperature, the viscosity of the lubricating oil decreases with the increase of temperature, and an excessively low viscosity of the lubricating oil will lead to insufficient lubrication, aggravating the friction between the screw, the bearing and other components in the compressor 101 and affecting normal operation of the compressor 101.

In view of the problems in the operating principle and refrigeration cycle of the refrigeration system 100, one or more embodiments of the disclosure provides a refrigeration system 200.

FIG. 2 is a schematic diagram of a refrigeration system according to one or more embodiments of the disclosure.

FIG. 3 is a schematic diagram of a heat exchange system according to one or more embodiments of the disclosure.

As shown in FIG. 2, the refrigeration system 200 in some embodiments comprises a heat exchange system 1, and a compressor 201, an oil separator 205 and an evaporator 204 in the refrigeration system 200 belong to the heat exchange system 1.

The compressor 201 is provided with a suction inlet A1 and an outlet A2, the evaporator 204 is provided with an inlet B1 and an outlet B2, and the oil separator 205 is provided with an inlet C1, a refrigerant outlet C2 and a mixture outlet C3.

The suction inlet A1 of compressor 201 is connected to outlet B2 of evaporator 204, and outlet A2 of compressor 201 is connected to the inlet C1 of oil separator 205. The inlet B1 of the evaporator 204 is indirectly connected to the refrigerant outlet C2 of the oil separator 205, and the outlet B2 of the evaporator 204 is connected to the suction inlet A1 of the compressor 101.

The inlet C1 of the oil separator 205 is connected to the outlet A2 of the compressor 201, and the oil separator 205 receives a high-temperature and high-pressure refrigerant gas mixed with lubricating oil from the compressor 201 and separates the high-temperature and high-pressure refrigerant gas from the lubricating oil. The refrigerant gas separated out by the oil separator 205 returns into a cycle of the refrigeration system 200 from the refrigerant outlet C2 of the oil separator 205, and sequentially flows through a condenser 202, an expansion valve 203 and the evaporator 204. The mixture outlet C3 of the oil separator 205 is used for discharging an oil and refrigerant mixture obtained by separation.

As shown in FIGS. 3 and 5, in some embodiments of the disclosure, the heat exchange system 1 further comprises a heat exchanger 2, an inlet line 3, a first regulating device 4 and an outlet line 5.

A refrigerant circulates in the evaporator 204. The refrigerant flows into the evaporator 204 via the inlet B1 of the evaporator 204, absorbs heat in the evaporator 204, then flows out of the evaporator 204 via the outlet B2 of the evaporator 204, and finally flows to the inlet A1 of the compressor 101. The superheat of the refrigerant is a difference between the temperature of the refrigerant flowing into the suction inlet A1 of compressor 101 and the evaporating temperature of the refrigerant.

The heat exchanger 2 comprises a primary-side 7 and a secondary-side 8. A heat exchange line comprising a primary-side line between an oil inlet 11 and outlet 12 of the heat exchanger and a secondary-side line between a refrigerant inlet 9 and outlet 10 of the heat exchanger are arranged in the heat exchanger 2, and the inlet line 3 is connected to a heat-exchange outlet B3 of the evaporator 204 and the secondary-side line of the heat exchange line and is used for guiding part of the refrigerant into the secondary-side line of the heat exchange line in the heat exchanger 2 from the evaporator 204. The first regulating device 4 is arranged on the inlet line 3 and used for increasing the pressure of the refrigerant from the evaporator 204 and pumping the refrigerant into the secondary-side line of the heat exchange line in the heat exchanger 2 for heat exchange. The outlet line 5 is connected to the suction inlet A1 of the compressor 201 (the outlet B2 of the evaporator 104) and the secondary-side line of the heat exchange line in the heat exchanger 2 and used for returning the refrigerant, that is heated by heat exchange in the heat exchanger 2, into the compressor 201.

In some embodiments, the first regulating device 4 is configured as an air pump, preferably a low-lift pump. In addition, in actual use of the disclosure, the first regulating device 4 may be one or a combination of multiple of a gear pump, a centrifugal pump, a piston pump, a hydraulic plunger pump, a pneumatic diaphragm pump, a booster pump, a steam-jet pump. The disclosure has no limitation in this aspect as long as the first regulating device 4 can increase the pressure of the refrigerant from the outlet of the evaporator 204 to ensure that the refrigerant can overcome the resistance in the inlet line 3, the heat exchanger 2 and the outlet line 5 to be pumped into the heat exchanger 2 for heat exchange and then flow to the suction inlet A1 of the compressor 201.

At the suction inlet A1 of the compressor 201, part of the refrigerant, that is heated by heat exchange in the heat exchanger 2, is mixed with part of the refrigerant discharged from the outlet B2 of the evaporator 204, such that the temperature of the refrigerant flowing into the suction inlet A1 of the compressor 201 is increased. The difference between the temperature of the refrigerant flowing into the suction inlet A1 of the compressor 201 and the evaporating temperature of the refrigerant is increased, that is, the superheat of the refrigerant is increased, thus avoiding liquid slugging caused by the refrigerant entering the compressor 201 in a liquid state in case of insufficient superheat.

Moreover, in some embodiments of the disclosure, the high-temperature and high-pressure oil and refrigerant mixture from the oil separator 205 flows to the heat exchanger 2 via the mixture outlet C3 of the oil separator 205, wherein the oil and refrigerant mixture is lubricating oil containing a small quantity of refrigerant gas. The lubricating oil flows through the primary-side line of the heat exchange line in the heat exchanger 2, and the temperature of the lubricating oil in the oil separator 205 is higher than the temperature of the refrigerant at the outlet of the evaporator 204. In this way, in the heat exchanger 2, the lubricating oil flowing through the primary-side line of the heat exchange line in the heat exchanger 2 exchanges heat with the refrigerant flowing through the secondary-side line of the heat exchange line in the heat exchanger 2, such that the temperature of the refrigerant is increased, and the temperature of the high-temperature lubricating oil is decreased, thus increasing the viscosity of the lubricating oil. The high-viscosity lubricating oil returns into the compressor 201 via a lubricating oil inlet A3 of the compressor 201 to be used for lubrication in the compression process, thus effectively improving the lubrication effect, reducing abrasion of the compressor 101 in operation, and prolonging the service life of the compressor 201.

In some embodiments, the heat exchanger 2 is preferably a plate heat exchanger, rectangular thin channels (the primary-side line and the secondary-side line) are formed between multiple plates in the plate heat exchanger, high-temperature fluid flowing through the primary-side line is not in contact with low-temperature fluid flowing through the secondary-side line, and the high-temperature fluid exchanges heat with the low-temperature fluid by means of the plates. The plate heat exchanger has high heat-exchange efficiency and a compact structure and occupies a small space.

Optionally, in some embodiments of the disclosure, a temperature difference between the refrigerant in the inlet line 3 and the refrigerant in the outlet line 5 is within 20-40° C. If the temperature of the refrigerant at the outlet of the evaporator 204 is about 60° C., the temperature of the refrigerant in the outlet line 5 can be increased to, for example, about 90° C. (80° C.-100° C.) after heat exchange in the heat exchanger 2. Further, the refrigerant (for example, at a temperature of 90° C.) in the outlet line 5 and the refrigerant (for example, at a temperature of 60° C.) discharged from the outlet B2 of the evaporator 204 are mixed at the suction inlet A1 of the compressor 201, so the temperature of the refrigerant entering the compressor 201 is at least 60° C. or higher, for example, 61° C.-62° C. In this way, the temperature of the refrigerant entering the compressor 201 can be increased by 1-2° C., that is, the suction superheat of the refrigerant entering the compressor 201 is increased by 1-2° C., thus ensuring that the refrigerant enters the compressor 201 in a gaseous state.

Of course, 1-2° C. mentioned here is merely an example, and the actual temperature rise is not limited to this. By controlling the flow rate and temperature of the refrigerant in the inlet line 3, the temperature and flow rate of the oil and refrigerant mixture flowing through the heat exchanger 2 and other parameters, the suction superheat of the refrigerant can be regulated properly.

In some embodiments of the disclosure, the temperature difference of the oil and refrigerant mixture before and after flowing through the heat exchange line in the heat exchanger 2 is within 20-50° C. If the temperature of the lubricating oil flowing out of the mixture outlet C3 of the oil separator 205 is 110° C., the temperature of the lubricating oil flowing into the compressor 101 after heat exchange in the heat exchanger 2 can be decreased to, for example, about 85° C. (90° C.-60° C.).

Optionally, in some embodiments of the disclosure, the heat exchange system 1 further comprises a second regulating device 6, wherein the second regulating device 6 is arranged on the outlet line 5 and used for regulating the flow rate of the refrigerant gas in the outlet line 5. In other words, the second regulating device 6 may be used for controlling the flow ratio of the high-temperature refrigerant (for example, at a temperature of 90° C.), subjected to heat exchange in the heat exchanger 2, at the suction inlet A1 of the compressor 201. After the high-temperature refrigerant is mixed with the low-temperature refrigerant (for example, at a temperature of 60° C.) discharged from the outlet B2 of the evaporator 204, the mixing ratio of the high-temperature refrigerant (for example, at a temperature of 90° C.) subjected to heat exchange in the heat exchanger 2 and the low-temperature refrigerant (for example, at a temperature of 60° C.) discharged from the outlet B2 of the evaporator 204 can be controlled to control the temperature of the refrigerant entering the compressor 101 (the suction inlet A1 of the compressor 101), that is, the superheat of the refrigerant entering the compressor 101 is controlled.

Specifically, when the second regulating device 6 is controlled to increase the flow rate of the gas in the outlet line 5, the proportion of the high-temperature refrigerant (for example, at a temperature of 90° C.) at the suction inlet A1 of the compressor 201 will be increased, and the temperature of the refrigerant entering the compressor 201 will be increased accordingly. On the contrary, when the second regulating device 6 is controlled to control decrease the flow rate of the gas in the outlet line 5, the proportion of the high-temperature refrigerant (for example, at a temperature of 90° C.) at the suction inlet A1 of the compressor 201 will be decreased, and the temperature of the refrigerant entering the compressor 201 will be decreased accordingly. Of course, when the second regulating device 6 is controlled to decrease the flow rate of the gas in the outlet line 5, if the temperature and flow rate of the oil and refrigerant flowing through the heat exchanger 2 remain unchanged, the temperature of the refrigerant flowing out of the outlet line 5 will be higher, for example, higher than 90° C. After a small quantity of the refrigerant at a higher temperature is mixed with the refrigerant flowing out of outlet B2 of evaporator 204, the refrigerant entering compressor 201 can still be maintained at a suitable temperature (superheat).

In the one or more embodiments of the disclosure, the heat exchange system 1 can increase the temperature of the refrigerant entering the compressor 201 and decrease the temperature of lubricating oil entering the compressor 201, thus increasing the suction superheat of the refrigerant in the compressor 201 and the viscosity of the lubricating oil in the compressor 201. In addition, the heat exchange system 1 performs heat exchange by means of heat generated in the circulation process of the refrigeration system 200, and no extra heating/refrigeration equipment is needed, such that the heat exchange system 1 has a low cost, a simple structure and a small size and is suitable for different types of refrigeration systems 200.

In actual use of the disclosure, the second regulating device 6 is a flow control valve. Specifically, the second regulating device 6 may be a capillary tube, a thermal expansion valve, an electronic expansion valve, or the like, and the disclosure has no limitation in this aspect.

FIG. 4 is a flow diagram of a heat exchange method according to some embodiments of the application.

Referring to FIG. 4, some embodiments of the application further provides a heat exchange method, which is applied to the heat exchange system 1. The heat exchange method comprises: a step S1 of heat exchange: pumping a refrigerant from the inlet line 3 into the secondary-side line of the heat exchange line in the heat exchanger 2 to exchange heat with an oil and refrigerant mixture flowing through the primary-side line of the heat exchange line in the heat exchanger 2; and a step S2 of discharging: discharging the refrigerant subjected to heat exchange to the suction inlet A1 of the compressor 201 by means of the outlet line 5.

By adopting the heat exchange method in some embodiments of the disclosure, the temperature of the refrigerant entering the compressor 201 can be increased, and the temperature of lubricating oil entering the compressor 201 can be decreased, thus increasing the suction superheat of the refrigerant in the compressor 201 and the viscosity of the lubricating oil in the compressor 201. In addition, the heat exchange method performs heat exchange by means of heat generated in the circulation process of the refrigeration system 200 and fulfills a good effect, and the steps of the heat exchange method can be performed easily and efficiently.

Optionally, in some embodiments of the application, the heat exchange method further comprises a step of regulation: regulating the pressure of the refrigerant and the flow rate of the refrigerant in the inlet line 3 and/or the outlet line 5 respectively by means of the first regulating device 4 arranged on the inlet line 3 and/or the second regulating device 6 arranged on the outlet line 5. In other words, the first regulating device 4 and the second regulating device 6 can respectively regulate the inlet pressure and output of the refrigerant in the heat exchanger 2, such that the temperature of the refrigerant flowing out of the heat exchanger 2 (the temperature of the refrigerant in the outlet line 5) can be controlled to a desired temperature by controlling the heat exchange amount of the refrigerant in the heat exchanger 2.

Specifically, when the first regulating device 4 and the second regulating device 6 are controlled to maintain a low flow rate of the refrigerant in the inlet line 3, a difference between the temperature of the refrigerant in the outlet line 5 and the temperature of the refrigerant in the inlet line 3 will be increased under the condition where the temperature and flow rate of the oil and refrigerant flowing through the heat exchanger 2 remain unchanged, and the superheat will be increased accordingly. On the contrary, when the first regulating device 4 and the second regulating device 6 are controlled to maintain a high flow rate of the refrigerant in the inlet line 3, the difference between the temperature of the refrigerant in the outlet line 5 and the temperature of the refrigerant in the inlet line 3 will be decreased under the condition where the temperature and flow rate of the oil and refrigerant flowing through the heat exchanger 2 remain unchanged, and the superheat will be decreased accordingly.

Optionally, in some embodiments of the disclosure, according to the heat exchange method, the temperature of the refrigerant in outlet line 5 is increased by 20-40° C., as compared with the temperature of the refrigerant in the inlet line 3.

Optionally, in some embodiments of the disclosure, according to the heat exchange method, the temperature difference of the oil and refrigerant mixture before and after flowing through the heat exchange line in the heat exchanger 2 is within 20-50° C.

Although the technical solution of the disclosure has been described above in conjunction with the accompanying drawings, those skilled in the art can easily understand that the protection scope of the disclosure is not limited to the above one or more embodiments. Equivalent modifications or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the disclosure, and all these modifications or substitutions should also fall within the protection scope of the disclosure.