Systems and Methods for Interlaced Microchannel Heat Exchanger Systems with Multiple Compressors of Different Sizes

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and benefit of U.S. provisional patent application no. 63/669,558 filed July 10, 2024, which is herein incorporated by reference.

TECHNICAL FIELD

The present disclosure is generally in the field of air systems. For example, systems and methods are provided herein for air systems with interlaced microchannel heat exchangers for use with multiple compressors having different sizes.

BACKGROUND

Commercial buildings, homes, or other structures can commonly be equipped with one or more air systems for heating and/or cooling, such as a heat pump system or an air conditioner system. These air systems can include an indoor heat exchanger unit and an outdoor heat exchanger unit in fluid communication via a refrigerant circuit. To improve efficiency and otherwise satisfy certain regulatory standards, multi-circuit air systems have been developed with more than one compressor. To achieve energy savings and improve efficiency, when demand is low, only one compressor is used, and when demand is high, both compressors are used. Due to limitations in heat exchanger design requiring symmetry in the microchannel heat exchangers, such air systems have been limited to compressors of the same size (e.g., energy output) and having the same charge quantity. As a result, such air systems are limited in their ability to reduce operation based on demand.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic view of an example refrigerant circuit.

FIG. 2illustrates a partial cross-sectional view of an example microchannel heat exchanger.

FIG. 3 illustrates a schematic view of an example air system having dual refrigerant circuits and multiple compressors with different sizes.

FIG. 4 illustrates a partial cross-sectional view of a microchannel heat exchanger connected to dual refrigerant circuits and having a disproportionate number of microchannel rows for the refrigerant circuits.

FIG. 5 illustrates a partial cross-sectional view of a microchannel heat exchanger connected to dual refrigerant circuits and having microchannel rows of different sizes.

FIGS. 6A-6B illustrates cross-sectional views of a microchannel heat exchanger connected to dual refrigerant circuits with a disproportionate number of passages with different sizes.

DETAILED DESCRIPTION

Multi-circuit vapor compression cycle systems include a plurality of fluidly separated refrigerant circuits. Each of the refrigerant circuits may flow through a single indoor heat exchanger (e.g., evaporator) and a single outdoor heat exchanger (e.g., condenser). As will be described more fully herein, refrigerant may be selectively and independently flowed through each individual refrigerant circuit. Each refrigerant circuit may include a compressor and the compressors may be different sizes. With compressors of different sizes, the vapor compression cycle system may achieve full-load efficiency while also selectively providing part-load efficiency (e.g., using only the smaller compressor). That is, at part-load, the air system may be configured to selectively operate fewer than the total number of refrigerant circuits. Each compressor may be a multi-stage and/or variable speed compressor, and the operation of each compressor may be selectively adjusted according to demand. The vapor compression cycle system may thus improve efficiency and permit operation at a lower cost.

A "vapor compression system" may broadly encompass any system that is configured to heat and/or cool a conditioned space, heat and/or cool a fluid that is provided to a load, and/or perform any other actions associated with a vapor compression cycle. Non-limiting examples of types of vapor compression systems can include air conditioners (e.g., no reversing valve, only provides cooling mode), heat pumps (e.g., air source or geothermal; has a reversing valve and operates in both heating and cooling modes), heat pump water heaters, integrated heat pump water heaters, split system heat pump water heaters, heat pump water heaters with a circulation pump and a brazed plate heat exchanger, split systems, packaged systems, mini-splits, PTACs, window units, vertical packaged systems, VRF systems, etc. Reference may be made herein to "air systems" (or the like), however, this is not intended to be limiting and any other type of vapor compression cycle system may be applicable.

For example, a vapor compression system may generally include components that combine to form a refrigerant loop that is used to produce conditioned air that is circulated throughout the conditioned space by the vapor compression system. For example, the refrigerant loop may include an indoor heat exchanger coil, an outdoor heat exchanger coil, a compressor, and an expansion valve (however, these components may vary, depending on the specific vapor compression system).

Continuing this example, during the operation of this exemplary vapor compression system in a cooling mode, warm indoor air is pulled (or pushed) over the indoor heat exchanger coil (which may be the evaporator coil of the vapor compression system) by a fan of the vapor compression system. As the liquid refrigerant inside the indoor heat exchanger coil converts to gas, heat is absorbed from the indoor air into the refrigerant, thus cooling the air that is pulled over the indoor heat exchanger coil. The fan is then operated to pull the cooled air into a conditioned space (such as a residential home or commercial establishment) that is being cooled by the air conditioning system. In some instances, this cooled air may be distributed throughout the conditioned space using ductwork installed within the conditioned space. The refrigerant gas then passes into the compressor. The compressor pressurizes the refrigerant gas and sends the refrigerant into the outdoor heat exchanger coil, which may operate as a condenser coil. A fan pulls outdoor air through the outdoor heat exchanger coil, allowing the air to absorb heating energy from the home and release it outside. During this process, the refrigerant is converted back to a liquid. The refrigerant then travels back to the indoor heat exchanger coil. The refrigerant passes through an expansion valve, which regulates the flow of refrigerant into the indoor heat exchanger coil. The cold refrigerant then absorbs more heat from the indoor air and the cycle repeats.

Likewise, in a standard heating mode, a reversing valve may be transitioned to direct refrigerant from the compressor to the indoor heat exchanger coil as opposed to directing it to the outdoor heat exchanger coil, as is done in the cooling mode. In a heating mode, the refrigerant absorbs heat from the outdoor air through the outdoor heat exchanger coil. The refrigerant then passes through the compressor, which compresses (and thus warms) the refrigerant. The heated refrigerant is transferred to the indoor heat exchanger coil. One or more fans push or pull air over the indoor heat exchanger coil, thereby transferring heat from the indoor heat exchanger coil to the conditioned space. Ductwork then directs the conditioned air throughout the conditioned space to heat the conditioned space. One or more supplemental heating sources, such as an electric heating kit, and/or a gas furnace with a heat exchanger in the indoor coil portion, may additionally be used. This description is merely exemplary and the specific operation of the vapor compression system may vary depending on the specific vapor compression system.

The disclosed technology will be described more fully hereinafter with reference to the accompanying drawings. This disclosed technology can, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein. The components described hereinafter as making up various elements of the disclosed technology are intended to be illustrative and not restrictive. Such other components not described herein may include, but are not limited to, for example, components developed after the development of the disclosed technology.

In the following description, numerous specific details are set forth. But it is to be understood that examples of the disclosed technology can be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail in order not to obscure an understanding of this description. References to "one embodiment," "an embodiment," "example embodiment," "some embodiments," "certain embodiments," "various embodiments," "one example,' "an example," "some examples," "certain examples," "various examples," etc., indicate that the embodiment(s) and/or example(s) of the disclosed technology so described may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Further, repeated use of the phrase "in one embodiment" or the like does not necessarily refer to the same embodiment, example, or implementation, although it may.

Throughout the specification and the claims, the following terms take at least the meanings explicitly associated herein, unless the context clearly dictates otherwise. The term "or" is intended to mean an inclusive "or." Further, the terms "a," "an," and "the" are intended to mean one or more unless specified otherwise or clear from the context to be directed to a singular form.

Unless otherwise specified, the use of the ordinal adjectives "first," "second," "third," etc., to describe a common object, merely indicate that different instances of like objects are being referenced and are not intended to imply that the objects so described should be in a given sequence, either temporally, spatially, in ranking, or in any other manner.

Throughout this disclosure, reference is made to the accompanying drawings in which like numerals represent like elements. Certain groups of elements and/or components are referenced generally using a common numeral, while specific instances of the element and/or component are referenced using the numeral followed by a corresponding alphanumeric reference. For example, this disclosure references refrigerant circuits generally using reference numeral 305, whereas reference to specific refrigerant circuits is made herein using reference numerals 305a and 305b.

Unless otherwise specified, all ranges disclosed herein are inclusive of stated end points, as well as all intermediate values. By way of example, a range described as being "between approximately 2 and approximately 4" includes the values 2 and 4 and all intermediate values within the range. Likewise, the expression that a property "can be in a range from approximately 2 to approximately 4" (or "can be in a range from 2 to 4") means that the property can be approximately 2, can be approximately 4, or can be any value therebetween.

Referring to FIG. 1, air conditioner systems can include a refrigerant circuit that includes a compressor, a condenser, an expansion valve, and an evaporator, which can operate to provide a cooling effect in an indoor space by transferring heat from the indoor space to the refrigerant via the evaporator and transferring heat from the refrigerant to an outdoor space via the condenser. As another example, heat pump systems can include a refrigerant circuit similar to the one shown in FIG. 1, but also including a reversing valve or another component or system configured to selectively change the direction of refrigerant flow through the refrigerant circuit. Thus, the heat pump system can have a cooling mode in which the indoor heat exchanger operates as an evaporator and the outdoor unit operates as a condenser (i.e., operating as an air conditioner system), and the heat pump system can have a heating mode in which the indoor heat exchanger operators as a condenser and the outdoor heat exchanger operates as an evaporator (i.e., operating as a heating system).

To improve the efficiency and performance of air systems, microchannel heat exchangers can be used. Referring to the partial cross-sectional view shown in FIG. 2, microchannel heat exchangers are heat exchangers that direct the flow of refrigerant through ports (e.g., passages) that are smaller in internal diameter than conventional finned heat exchanger tubes (e.g., less than or equal to approximately 1 mm in diameter). Microchannel heat exchangers can provide a variety of advantages over conventional finned heat exchanger tubes including higher heat transfer ratios, reduced refrigerant charge, smaller and more compact design, lower weight, and higher energy efficiency of the overall system.

Referring now to FIG. 3, a schematic view of an example air system having compressors with different sizes is depicted, in accordance with the disclosed technology. Air system 300 may be a heat pump system, air conditioning system, and/or any other system for heating and/or cooling air and/or water using a refrigerant (for example, any type of vapor compression cycle system mentioned above or otherwise). Air system 300 may have multiple stages and may adjust operation for a desired full load capacity or one or more part load capacities. For example, air system 300 may have three or more stages. In another example, air system 300 may have four, five, six, or more stages. Embodiments may include compressors with multiple stages (e.g., one compressor single stage and the other a 2-stage compressor, etc.) and/or combinations of compressors with different numbers of stages.

As shown in FIG. 3, air system 300 may include refrigerant circuits 305. Specifically, air system 300 may include refrigerant circuit 305a and refrigerant circuit 305 b, which may be fluidly separated refrigerant circuits. While two refrigerant circuits are illustrated in FIG. 3, more than two refrigerant circuits may be included in air system 300 (e.g., three circuits, four circuits, etc.).

Each of the refrigerant circuits 305 may be configured to pass through an indoor heat exchanger 302, which may be a single interlaced microchannel heat exchanger (iMCHX). Alternatively, indoor heat exchanger 302 may be any suitable interlaced (e.g., intertwined) heat exchanger (e.g., with channels larger than 1 mm). Air system 300 may further include blower 314, which may be any suitable blower or fan configured to direct airflow across indoor heat exchanger 302. Similarly, refrigerant circuits 305 may be configured to pass through outdoor unit 304, which may be a single interlaced microchannel heat exchanger (iMCHX). Alternatively, indoor heat exchanger 302 may be any suitable interlaced (e.g., intertwined) heat exchanger. Blower 315 may be any suitable blower or fan configured to direct airflow across outdoor heat exchanger 304. The interlaced heat changers may include alternating rows connected to the different refrigerant circuits to efficiently exchange thermal energy across the entire heat exchanger.

As will be appreciated by those having skill in the art, the interlaced (e.g., intertwined) aspect of the iMCHXs enables air system 300 to connect multiple, fluidly separated refrigerant circuits though a single indoor heat exchanger (e.g., acting as an evaporator) and a single outdoor heat exchanger (e.g., acting as a condenser). This configuration provides a high part-load efficiency compared to traditional microchannel heat exchangers by increasing the available surface area and airflow for heat transfer. One or both of the indoor iMCHX and outdoor iMCHX can have a counter-flow circuit configuration, and/or one or both of the indoor iMCHX and outdoor iMCHX can have a parallel-flow circuit configuration.

Refrigerant circuits 305 may each contain different volumes of refrigerant (e.g., different charge quantities). Each of the refrigerant circuits 305 may include the same type of refrigerant (e.g., R-410A, R-454B, etc.). Conversely, one, some, or all of the refrigerant circuits 305 can include a different type of refrigerant. It will be understood by one skilled in the art that air system 300 may further include a reversing valve or similar mechanism to reverse refrigerant flow such that the evaporator may operate as a condenser and the condenser as an evaporator.

Each of refrigerant circuits 305 may include its own compressor and expansion valve. For example, refrigerant circuit 305a may include compressor 306, which may be any suitable compressor for heating and cooling designed to compress the refrigerant, and expansion valve 312, which may be any suitable expansion valve designed to facilitate pressure reduction and expansion of the refrigerant. Similarly, refrigerant circuit 305b may include compressor 308, which may be any suitable compressor for heating and cooling designed to compress the refrigerant, and expansion valve 310, which may be any suitable expansion valve designed to facilitate pressure reduction and expansion of the refrigerant.

Refrigerant circuit 305a may guide refrigerant (e.g., via piping) from outdoor unit 304 to compressor 306, to indoor unit 302, to expansion valve 312, and back to outdoor unit 304. Refrigerant circuit 305b may guide a separate volume of refrigerant from output unit 304, to compressor 308, to indoor unit 302, to expansion valve 310, and back to outdoor unit 304. Compressor 306 may be larger in size (e.g., energy and/or volume output) than compressor 308. For example, compressor 308 may have a rating of 30k BTU and compressor 306 may have a rating of 60k BTU. However, different sized compressors may be used and/or compressors may have different size ratios or proportions.

Referring now to FIG. 4, a partial cross-sectional view of a microchannel heat exchanger connected to dual refrigerant circuits and having a disproportionate number of microchannel rows for the refrigerant circuits is illustrated. Specifically, heat exchanger 400 may include rows of microchannels separated by fins. Heat exchanger 400 may be heat exchanger 302 and/or heat exchanger 304 of FIG. 3. For example, heat exchanger 400 may be an outdoor unit.

The microchannels may be passages (e.g., ports) that extend the length of each row. For example, multiple channels (e.g., two, three, four, five, six, ten, twelve, etc.) may extend the length of the row. The microchannels may be connected to one another and/or to the refrigerant circuits via one or more manifolds 402. For example, manifolds may be positioned on either end of the rows of microchannels. It will be understood by one of skill in the art that the rows may alternatively have larger channels or passages than microchannels (e.g., larger than 1 mm in diameter and/or width). Fins 408 may be designed to exchange thermal energy with the rows of microchannels and the air in the exterior environment.

As shown in close up view 405, rows 406 having passages 412 may be coupled to, be in fluid communication with, and/or otherwise correspond to a primary refrigerant circuit with a large compressor and rows 404 having passages 410 may be coupled to, be in fluid communication with, and/or otherwise correspond to a secondary refrigerant circuit with smaller compressor, smaller than the large compressor of the primary refrigerant circuit. Alternatively, passages 412 may be coupled to, be in fluid communication with, and/or otherwise correspond to the second refrigerant circuit and passages 410 to the primary refrigerant circuit.

To accommodate a larger charge quantity in the primary refrigerant circuit with the larger compressor, a greater number of rows 406 connected to the primary refrigerant circuit may be included in heat exchangers 400. As shown in FIG. 4, rows 404 may be interspersed between every two rows of rows 406. As a result, the ratio of rows 406 to rows 404 may be 2-to-1. However, any other ratios of numbers of rows may be used to account for the different charge quantities and/or different compressor sizes in the primary and secondary refrigerant circuits.

As shown in shown in FIG. 4, each of rows 406 and rows 404 may include the same number of passages (e.g., ports) and/or the passages may be the same size. Alternatively, rows 406 and rows 404 may include a different number of passages and/or the passages of each of rows 406 may have a different size. Passage size refers to the cross-sectional area of a passage, for example.

Referring now to FIG. 5, a partial cross-sectional view of a microchannel heat exchanger connected to dual refrigerant circuits and having microchannel rows for the refrigerant circuits of different sizes is illustrated. Similar to heat exchanger 500 of FIG. 4, heat exchanger 500 may include rows of microchannels separated by fins. Heat exchanger 500 may be heat exchanger 302 and/or heat exchanger 304 of FIG. 3. For example, heat exchanger 500 may be an outdoor unit.

The microchannels may be passages (e.g., ports) that extend the length of each row a. The microchannels may be connected to one another and/or to the refrigerant circuits via one or more manifolds 502. For example, manifolds may be positioned on either end of the rows of microchannels of heat exchanger 500. It will be understood to one of skill in the art that the rows may alternatively have larger channels or passages than microchannels. Fins 508 may be designed to exchange thermal energy with the rows of microchannels and the air in the exterior environment.

As shown in close up view 505, rows 506 having passages 512 may be coupled to, may be in fluid communication with, and/or otherwise correspond to a primary refrigerant circuit with a small compressor and rows 504 having passages 510 may be coupled to, be in fluid communication with, and/or otherwise correspond to a secondary refrigerant circuit with large compressor, larger than the small compressor of the primary refrigerant circuit. Alternatively, passages 512 may be coupled to, be in fluid communication with, and/or otherwise correspond to the secondary refrigerant circuit and passages 410 the primary refrigerant circuit.

To accommodate a larger charge quantity of the secondary refrigerant circuit with the larger compressor, passages 510 may be larger than passages 512 of rows 506. For example, passages 510 may be twice as large as passages 512. In one example, passages 512 may optionally have a diameter larger than 1 mm. However, any other sizes and/or ratios of passage size may be used to account for the different charge quantities and/or different compressor sizes in the primary and secondary refrigerant circuits. As shown in FIG. 5, row 504 and 506 may alternate in heat exchanger 500, which may include the same number of rows 504 and rows 506. Alternatively, heat exchanger 500 may include a different number of rows 504 and 506. Heat transfer capacities and corresponding heat distribution across a coil may change based on the different relative sizing of the passages and/or dimensions of the passages.

As shown in shown in FIG. 5, each of rows 506 and rows 504 may include a different number of passages (e.g., four passages in row 504 and six passages in row 506) and/or the passages may be a different size. However, a different number of passages may be positioned within rows 504 and/or 506. Alternatively, rows 506 and rows 504 may include a passages having the same size, but rows 504 may include more passages than row 506. Passage size refers to the cross-sectional area of a passage, for example.

Referring now to FIGS. 6A-6B, cross-sectional views of a microchannel heat exchanger connected to dual refrigerant circuits with a disproportionate number of passages and disproportionately sized passages in the same row of a heat exchanger are illustrated. For example, the heat exchanger may be similar to heat exchangers 400 and 500 of FIGS. 4 and 5, respectively, and may include manifolds, rows with passages therein, and fins between each row.

Referring now to FIG. 6A, a cross-sectional view of a row of a heat exchanger, such as the heat exchanger illustrated in FIGS. 2 or 4, but with rows connected to multiple charge circuits, is illustrated. For example, row 604 may be microchannel row having passages (e.g., ports) extending the length of the row. As shown in FIG. 6A, row 604 may include alternating passages from different circuits. Specifically, passages 604 and 605 may correspond to a primary charge circuit including a large compressor (e.g., refrigerant charge circuit 305a of FIG. 3) and passage 606 may correspond to a secondary charge circuit including a small compressor (e.g., refrigerant charge circuit 305b of FIG. 3). The larger charge quantity in the primary circuit as compared to the secondary circuit may be accounted for in row 604 having more passages connected to (e.g., in fluid communication with) the primary circuit than the secondary circuit. As shown in FIG. 6A, all passages may be the same size (e.g., correspond to the same cross- sectional area).

Referring now to FIG. 6B, a cross-sectional view of a row of a heat exchanger, such as the heat exchanger illustrated in FIGS. 2 or 4, but with channels having multiple charge circuits in the same row, is illustrated. For example, row 622 may be microchannel row having passages (e.g., ports) extending the length of the row. As shown in FIG. 6B, row 622 may include alternating passages from different circuits. Specifically, passage 624 may correspond to a primary charge circuit including a large compressor (e.g., refrigerant charge circuit 305a of FIG. 3) and passage 626 may correspond to a secondary charge circuit including a small compressor (e.g., refrigerant charge circuit 305b of FIG. 3). The larger charge quantity in the primary circuit as compared to the secondary circuit may be accounted for in row 622 having larger passages (e.g., corresponding to a greater cross-sectional area) connected to (e.g., in fluid communication with) the primary circuit and smaller passages connected to the secondary circuit. As shown in FIG. 6A, row 622 may include the same number of passages connected primary circuit as connected to the secondary circuit.

Although embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as illustrative forms of implementing the embodiments. Conditional language, such as, among others, "can," "could," "might," or "may," unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments could include, while other embodiments do not include, certain features, elements, and/or steps. Thus, such conditional language is not generally intended to imply that features, elements, and/or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements, and/or steps are included or are to be performed in any particular embodiment.