Microchannel Heat Exchanger with Varying Fin Density

This application is a continuation of U.S. application Ser. No. 17/311,256, entitled “MICROCHANNEL HEAT EXCHANGER WITH VARYING FIN DENSITY,” filed Jun. 4, 2021, which is a U.S. National Stage Application of PCT International Application No. PCT/US2019/064499, entitled “MICROCHANNEL HEAT EXCHANGER WITH VARYING FIN DENSITY,” filed Dec. 4, 2019, which claims the benefit of and priority from U.S. Provisional Patent Application No. 62/776,303, entitled “MICROCHANNEL HEAT EXCHANGER WITH VARYING FIN DENSITY,” filed Dec. 6, 2018, each of which is hereby incorporated by reference in its entirety for all purposes.

This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

Chiller systems, or vapor compression systems, utilize a working fluid, typically referred to as a refrigerant, which changes phases between vapor, liquid, and combinations thereof in response to exposure to different temperatures and pressures associated with operation of the vapor compression system. For example, an HVAC&R system may include a chiller, which is a type of vapor compression system, which circulates a refrigerant to remove heat from a flow of working fluid in a heat exchange relationship with the refrigerant in a chiller evaporator.

A vapor compression system may include a heat exchanger configured to transfer heat between the working fluid and a conditioned fluid. For example, the heat exchanger may be configured to cool the conditioned fluid by placing the conditioned fluid in thermal communication with the working fluid and enabling the working fluid to absorb heat from the conditioned fluid. The heat exchanger may also be configured to cool the working fluid by placing the working fluid in thermal communication with a cooling fluid, such as ambient air, where the cooling fluid absorbs heat from the working fluid. In some embodiments, the heat exchanger may be a microchannel heat exchanger that includes several microchannel tubes positioned adjacent to one another. A set of fins may be disposed between adjacent microchannel tubes to facilitate heat transfer between the working fluid and another fluid. In certain traditional microchannel heat exchangers, the orientation of each set of fins is the same between each set of adjacent microchannel tubes, which may cause an undesirable amount of heat transfer across a profile of the heat exchanger.

A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.

In one embodiment, a heat exchanger of a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system includes a plurality of microchannel tubes, where each microchannel tube of the plurality of microchannel tubes is configured to direct refrigerant therethrough, and a plurality of fin sets, where each fin set of the plurality of fin sets is disposed between corresponding adjacent microchannel tubes of the plurality of microchannel tubes. Additionally, each fin set of the plurality of fin sets includes a respective fin density based on a location of the respective fin set along a height of the heat exchanger.

In another embodiment, a heat exchanger of a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system includes a plurality of microchannel coils arranged along a height of the heat exchanger, where each microchannel coil of the plurality of microchannel coils extends along a length of the heat exchanger, and a plurality of fin sets, where each fin set of the plurality of fin sets is disposed between a corresponding pair of adjacent microchannel coils of the plurality of microchannel coils, wherein each fin set of the plurality of fin sets extends along the length of the heat exchanger. Additionally each fin set of the plurality of fin sets includes a fin density that is selected based at least in part on a respective location of the fin set along the height of the heat exchanger.

In another embodiment, a heat exchanger includes a first section and a second section. The first section includes a plurality of first microchannel tubes and a plurality of first fin sets disposed between corresponding adjacent first microchannel tubes of the plurality of first microchannel tubes, where each first fin set of the plurality of first fin sets includes a first number of fins. The second section includes a plurality of second microchannel tubes and a plurality of second fin sets disposed between corresponding adjacent second microchannel tubes of the plurality of second microchannel tubes, where each second fin set of the plurality of second fin sets includes a second number of fins, where the second number of fins is less than the first number of fins.

Embodiments of the present disclosure include a microchannel heat exchanger with varying fin densities at different sections of the microchannel heat exchanger, which may produce an improved velocity profile of fluid directed across the microchannel heat exchanger. For example, varying the fin density of the microchannel heat exchanger may enable a velocity of the fluid to vary throughout the microchannel heat exchanger and achieve target velocities at various positions of the microchannel heat exchanger. In general, as the refrigerant flows through the microchannel tubes, heat is transferred between the refrigerant and the microchannel tubes. Further, as the fluid is directed across the microchannel tubes, heat is transferred between the fluid and the microchannel tubes. As previously mentioned, a set of fins may be disposed between adjacent microchannel tubes to increase an amount of heat to transfer between the refrigerant and the fluid. Specifically, in addition to transferring heat between the refrigerant and the microchannel tubes, heat may be transferred between the refrigerant and the fins across and/or along a length of each microchannel tube. As the fluid is directed across the microchannel tubes, the fluid is placed in contact with the microchannel tubes and with the fins to absorb or transfer heat from the refrigerant with both the microchannel tubes and the fins. In this manner, the fins increase the surface area that the fluid contacts, to exchange heat with the refrigerant.

As should be understood, an improved or desired velocity profile of fluid directed across the microchannel heat exchanger may increase efficiency of heat transfer between refrigerant flowing within the microchannel tubes and a fluid (e.g., air) directed across the microchannel tubes. In general, the velocity of the fluid directed across the microchannel tubes may determine an amount of heat transferred between the refrigerant and the fluid. For example, directing the fluid at a higher velocity may increase the amount of heat transferred between the refrigerant and the fluid. Based on a design of the heat exchanger, it may be desirable to direct the fluid across the heat exchanger at particular velocities in certain areas or sections of the heat exchanger. For instance, the heat exchanger includes a first section where the refrigerant is initially supplied and has a greater capacity to exchange heat with the fluid. Furthermore, the heat exchanger includes a second section near an exit of the refrigerant where the refrigerant has a lower capacity to exchange heat with the fluid. Thus, it may be desirable to direct the fluid across the heat exchanger at a higher velocity at the first section as compared to the second section to enable a greater amount of thermal energy transfer between the fluid and the refrigerant. As an example, the improved velocity profile may be a substantially evenly distributed profile, a velocity profile that is a gradient relative to a length of the heat exchanger, a velocity profile that is symmetric relative to an axis of the heat exchanger, and/or any other suitable velocity profiles.

In some microchannel heat exchangers, the orientation of fins may be similar throughout the heat exchanger. Specifically, an angle of each fin with respect to the microchannel tube, a number of fins, a spacing of fins, a length of each fin, and/or other properties of the fins may be similar or the same throughout the heat exchanger. However, a uniform orientation of fins throughout the heat exchanger may cause an undesirable distribution of fluid passing across certain sections of the heat exchanger due to a position of a fan forcing the fluid across the heat exchanger with respect to the microchannel tubes and/or the fins. As a result, an efficiency of the heat exchanger and/or an amount of fluid directed across the heat exchanger may be reduced.

Accordingly, it is now recognized that varying the orientation of fins in different sections of the heat exchanger may increase a performance of the heat exchanger. For example, adjusting the number of fins in certain sections of the heat exchanger may produce an improved distribution of fluid flow throughout the heat exchanger. Enhancing the distribution of fluid flow may enable a greater amount of heat to transfer between the fluid and the refrigerant to increase the efficiency of the heat exchanger.

Turning now to the drawings,is a perspective view of an embodiment of a heating, ventilation, and air conditioning (HVAC) system for a buildingin a typical commercial setting. Such systems, in general, may be applied in a range of settings, both within the HVAC field and outside of the HVAC field. The HVAC systems may provide cooling to conditioned spaces of buildings, data centers, electrical devices, freezers, coolers, or other environments through vapor-compression refrigeration, absorption refrigeration, or thermoelectric cooling. In presently contemplated applications, HVAC systems may be used in residential, commercial, light industrial, industrial, and in any other application for heating or cooling a volume or enclosure, such as a residence, building, structure, and so forth. Moreover, the HVAC systems may be used in industrial applications, where appropriate, for cooling and heating of various fluids.

The HVAC system may include a chillerthat supplies a chilled liquid, which may be used to cool the building. The HVAC system may also include a boilerto supply warm liquid to heat the buildingand an air distribution system that circulates air through the building. As shown, the chilleris disposed on the roof of the building, and the boileris located in the basement; however, the chillerand boilermay be located in other equipment rooms or areas in or next to the building. The chillermay be an air cooled or water cooled device that implements a refrigeration cycle to cool water or other conditioning fluid. The chilleris housed within a structure that includes a refrigeration circuit, a free cooling system, and associated equipment such as pumps, valves, and piping. For example, the chillermay be single package rooftop unit that incorporates a free cooling system. The boileris a closed vessel in which water is heated. The water from the chillerand the boileris circulated through the buildingby water conduits. The water conduitsare routed to air handlerslocated on individual floors and within sections of the building.

The air handlersare coupled to ductworkthat is adapted to distribute air between the air handlersand may receive air from an outside intake (not shown). In some embodiments, the air handlersmay include a heat exchanger that is connected to the boilerand the chiller. The heat exchanger in the air handlermay receive either heated liquid from the boileror chilled liquid from the chiller, depending on the mode of operation of the HVAC system, to provide heated or cooled air to conditioned spaces within the building. Fans within the air handlersforce air across the heat exchangers and direct the conditioned air to environments within building, such as rooms, apartments, or offices, to maintain the environments at a designated temperature. A control device, shown here as including a thermostat, may be used to designate the temperature of the conditioned air. The control devicealso may be used to control the flow of air through and from the air handlers. Other devices may be included in the system, such as control valves that regulate the flow of water and pressure and/or temperature transducers or switches that sense the temperatures and pressures of the water, the air, and so forth. Moreover, control devices may include computer systems that are integrated with or separate from other building control or monitoring systems, and even systems that are remote from the building. The HVAC system is shown with a separate air handler on each floor of building, but in other embodiments, the HVAC system may include air handlersand/or other components that may be shared between or among floors.

is a schematic of an embodiment of an HVAC system, in accordance with the present techniques. For example, the HVAC systemmay be an air-cooled chiller. However, it should be appreciated that the disclosed techniques may be incorporated with a variety of other systems, such as water-cooled chillers, direct expansion HVAC systems, and so forth.

The HVAC system(e.g., vapor compression system) includes a refrigerant circuitconfigured to circulate a working fluid, such as refrigerant, therethrough with a compressor(e.g., a screw compressor) disposed along the refrigerant circuit. The refrigerant circuitalso includes a flash tank, a condenser, expansion valves or devices, and a liquid chiller or an evaporator. The components of the refrigerant circuitenable heat transfer between the working fluid and other fluids (e.g., a conditioning fluid, air, water, etc.) in order to provide cooling to an environment, such as an interior of the building.

Some examples of fluids that may be used as refrigerants in the vapor compression systemare hydrofluorocarbon (HFC) based refrigerants, for example, R-410A, R-407, R-134a, hydrofluoro-olefin (HFO), “natural” refrigerants like ammonia (NH3), R-717, carbon dioxide (CO2), R-744, or hydrocarbon based refrigerants, water vapor, refrigerants with low global warming potential (GWP), or any other suitable refrigerant. In some embodiments, the vapor compression systemmay be configured to efficiently utilize refrigerants having a normal boiling point of about 19 degrees Celsius (66 degrees Fahrenheit or less) at one atmosphere of pressure, also referred to as low pressure refrigerants, versus a medium pressure refrigerant, such as R-134a. As used herein, “normal boiling point” may refer to a boiling point temperature measured at one atmosphere of pressure.

The HVAC systemmay further include a control panel(e.g., controller) that has an analog to digital (A/D) converter, a microprocessor, a non-volatile memory, and/or an interface board. In some embodiments, the HVAC systemmay use one or more of a variable speed drive (VSDs)and a motor. The motormay drive the compressorand may be powered by the VSD. The VSDreceives alternating current (AC) power having a particular fixed line voltage and fixed line frequency from an AC power source, and provides power having a variable voltage and frequency to the motor. In other embodiments, the motormay be powered directly from an AC or direct current (DC) power source. The motormay include any type of electric motor that can be powered by the VSDor directly from an AC or DC power source, such as a switched reluctance motor, an induction motor, an electronically commutated permanent magnet motor, or another suitable motor.

The compressorcompresses a refrigerant vapor and delivers the vapor to an oil separatorthat separates oil from the refrigerant vapor. The refrigerant vapor is then directed toward the condenserthrough a discharge passage, and the oil is returned to the compressor. In some embodiments, the compressormay be a centrifugal compressor. The refrigerant vapor delivered by the compressorto the condensermay transfer heat to a cooling fluid (e.g., water or air) in the condenser. For example, the cooling fluid may be ambient airforced across heat exchanger coils of the condenserby condenser fans. The refrigerant vapor may condense to a refrigerant liquid in the condenseras a result of thermal heat transfer with the cooling fluid (e.g., the ambient air).

The refrigerant liquid exits the condenserand may flow through a first expansion device(e.g., expansion device, electronic expansion valve, etc.). The first expansion devicemay be a flash tank feed valve configured to control flow of the liquid refrigerant to the flash tank. The first expansion deviceis also configured to lower the pressure of (e.g., expand) the liquid refrigerant received from the condenser. During the expansion process, a portion of the liquid may vaporize, and thus, the flash tankmay be used to separate the vapor from the liquid received from the first expansion device. Additionally, the flash tankmay provide for further expansion of the liquid refrigerant because of a pressure drop experienced by the liquid refrigerant when entering the flash tank(e.g., due to a rapid increase in volume experienced when entering the flash tank).

The vapor in the flash tankmay exit and flow to the compressor. For example, the vapor may be drawn to an intermediate stage or discharge stage of the compressor(e.g., not the suction stage). A valve(e.g., economizer valve, solenoid valve, etc.) may be included in the refrigerant circuitto control flow of the vapor refrigerant from the flash tankto the compressor. In some embodiments, when the valveis open (e.g., fully open) additional liquid refrigerant within the flash tankmay vaporize and provide additional subcooling of the liquid refrigerant within the flash tank. The liquid refrigerant that collects in the flash tankmay be at a lower enthalpy than the liquid refrigerant exiting the condenserbecause of the expansion in the first expansion deviceand/or the flash tank. The liquid refrigerant may flow from the flash tank, through a second expansion device(e.g., expansion device, an orifice, etc.), and to the evaporator. In some embodiments, the refrigerant circuitmay also include a valve(e.g., drain valve) configured to regulate flow of liquid refrigerant from the flash tankto the evaporator. For example, the valvemay be controlled (e.g., via the control board) based on an amount of suction superheat of the refrigerant.

The refrigerant liquid delivered to the evaporatormay absorb heat from another cooling fluid, which may or may not be the same cooling fluid used in the condenser. The refrigerant liquid in the evaporatormay undergo a phase change from the refrigerant liquid to a refrigerant vapor. As shown in the illustrated embodiment of, the evaporatormay include a tube bundle fluidly coupled to a supply lineand a return lineconnected to a cooling load. The cooling fluid of the evaporator(e.g., water, ethylene glycol, calcium chloride brine, sodium chloride brine, or any other suitable fluid) enters the evaporatorvia return lineand exits the evaporatorvia supply line. The evaporatormay reduce the temperature of the cooling fluid in the tube bundle via thermal heat transfer with the refrigerant so that the cooling fluid may be utilized to provide cooling for a conditioned environment. The tube bundle in the evaporatorcan include a plurality of tubes and/or a plurality of tube bundles. In any case, the refrigerant vapor exits the evaporatorand returns to the compressorby a suction line to complete the cycle.

is a perspective view of an embodiment of the chillerthat may be utilized in the HVAC systemof. The chillermay include both a mechanical cooling system (e.g., a vapor-compression refrigeration cycle) and a free cooling system to enhance an efficiency of the chiller. In certain embodiments, the mechanical cooling system of the chillermay be an air-cooled variable-speed screw chiller and may use include the condenser, which may include multiple slabsthrough which refrigerant directed. As an example, the mechanical cooling system may be a two-circuit, variable-speed screw chiller with variable speed condenser fans(e.g., fans that may be used with one or more air-cooled heat exchangers) configured to direct the ambient airacross the slabs. Additionally, the chillermay include a free-cooling system that may be utilized alone, or in combination with, the mechanical cooling system (e.g., a vapor-compression refrigeration cycle).

In certain embodiments, the chillermay include a control system (e.g., the control board) configured to determine whether (and how) to operate the mechanical cooling system and/or the free cooling system based on a temperature of the ambient air(e.g., air in a surrounding environment of the chiller) and/or a cooling load demand (e.g., an amount of cooling demanded by a load). Accordingly, the chillermay operate the mechanical cooling system only (e.g., mechanical cooling mode), the free cooling system only (e.g., free cooling mode), or the mechanical cooling system and the free cooling system simultaneously (e.g., hybrid cooling mode) to meet the cooling load demand.

In some embodiments, the condenserand/or the evaporatormay be a microchannel type heat exchanger. In microchannel heat exchangers, an improved distribution of fluid passing across the heat exchanger may be desired to increase an amount of heat transfer between the fluid and the refrigerant. Accordingly, fins of the microchannel heat exchangers may be oriented or arranged to produce an improved distribution of fluid relative to certain traditional microchannel heat exchangers.

is a partial perspective view of a section of an embodiment of a microchannel heat exchanger, which is illustrated as being employed by one of the slabsof the condenser. Accordingly, the ambient airmay be directed across the microchannel heat exchangerto cool refrigerant flowing within the microchannel heat exchanger. Thus, the microchannel heat exchangermay be utilized in an air-cooled chiller. However, in additional or alternative embodiments, the microchannel heat exchangermay be utilized in any suitable chiller, such as a water-cooled chiller, a residential chiller, and so forth. In further embodiments, the microchannel heat exchangermay be utilized in another type of heat exchanger, such as the evaporator.

The microchannel heat exchangerincludes a headerconfigured to direct the refrigerant to a first microchannel tubeand a second microchannel tube, adjacent to the first microchannel tube. As illustrated in, the headeris oriented to direct the refrigerant in a generally vertical direction through an openingof the header. The first and second microchannel tubes,may be fluidly coupled to the headerto direct the refrigerant through the first and second microchannel tubes,at an angle relative to the flow through the header. For example, a lengthof the first and second microchannel tubes,may extend generally perpendicularly to a length or heightof the header, such that the flow of refrigerant through the first and second microchannel tubes,is substantially perpendicular to the flow of refrigerant through the header. In other embodiments, the first and second microchannel tubes,may be oriented at other suitable angles relative to the heightof the header. Each of the first and second microchannel tubes,may include a set of portsspanning the lengthof the first and second microchannel tubes,, where the refrigerant is configured to flow through each port. Additionally, a set of finsmay be disposed between the first microchannel tubeand the second microchannel tube. In some embodiments, the set of finsincludes individual fins connected to both the first microchannel tubeand the second microchannel tubeand oriented in a zigzag formation. That is, moving in a directionalong the lengthof the first and second microchannel tubes,, the set of finsmay alternate between first finsand second fins. Specifically, each first finmay extend from the second microchannel tubeat least partially in the directiontoward the first microchannel tube. Additionally, each second finmay extend from the first microchannel tubeat least partially in the directiontoward the second microchannel tube.

In some embodiments, the first finsmay be separate from the second fins, and each first finmay be in contact with or substantially proximate to an adjacent second fin. For example, each first finmay contact the first microchannel tubeat a pointof the first microchannel tube, and each second finmay extend from the pointtoward the second microchannel tubein the direction. Additionally, each second finmay contact the second microchannel tubeat a pointof the second microchannel tube, and each first finmay extend from the second microchannel tubeat the pointtoward the first microchannel tubein the direction. In additional or alternative embodiments, the first finsmay be connected to the second fins, such that the set of finsis continuous along the lengthand in contact with the first and second microchannel tubes,. In certain embodiments, each first finmay form an anglebetween each first finand the first microchannel tubeand/or second microchannel tube. Moreover, each second finmay form an anglebetween each second finand the first microchannel tubeand/or second microchannel tube. In some embodiments, the angleis approximately equal to the angle.

Additionally, the set of finsseparate the first and second microchannel tubes,by a distance. That is, each first finand each second finextends across the distanceto connect to the first and second microchannel tubes,. The distancemay enable a suitable number of microchannel tubes to be positioned along the heightof the headerwhile still permitting effective heat transfer between the set of finsand each microchannel tube,. That is, if the distanceis too small, fluid may not be directed across the set of finsand/or the microchannel tubes,at a desired rate to enable a sufficient rate of heat transfer between the fluid and the set of finsand/or the microchannel tubes,. However, increasing the distancemay reduce an available number of microchannel tubes,that may be disposed along the heightof the headerto achieve a desirable heat rate between the refrigerant and the fluid. Thus, the distancemay be selected, such as at 8 millimeters, to enable a desired amount of heat transfer between the refrigerant and the fluid in the heat exchanger.

While the refrigerant is directed through the first and second microchannel tubes,, a fluid (e.g., the ambient air) may be directed across the heat exchangerin a direction. For example, the fluid may be forced across the first and second microchannel tubes,and across the set of fins, placing the fluid in thermal communication with the refrigerant. When the refrigerant flows through the ports, heat may be exchanged between the refrigerant and an outer surfaceof the respective first and second microchannel tubes,and/or the set of fins. For example, if the microchannel heat exchangeris a condenser configured to cool the refrigerant, heat may transfer from the refrigerant to the outer surfaceand also from the refrigerant to the set of fins. As the fluid is directed across the heat exchangerto contact the first and second microchannel tubes,and the set of fins, heat transfers from the outer surfaceof the first and second microchannel tubes,and from the set of finsto the fluid. As such, heat is transferred from the refrigerant to the fluid to cool the refrigerant. If the microchannel heat exchangeris an evaporator configured to heat the refrigerant, heat may transfer from the fluid to the outer surfaceand to the set of fins. As the refrigerant is directed through the first and second microchannel tubes,, heat transfers from the outer surfaceof the first and second microchannel tubes,and from the set of finsto the refrigerant. Thus, heat is transferred from the fluid to the refrigerant to heat the refrigerant.

A pressure of the refrigerant may decrease as the refrigerant is directed through the lengthof the first and second microchannel tubes,. That is, the refrigerant may be pressurized to cause the refrigerant to enter the heat exchangerat a desired flow rate in a directioninto the openingof the header. A portion of the refrigerant may then be directed to flow through the first microchannel tubein the direction, and another portion of the refrigerant may be directed to flow through the second microchannel tubein the direction. When the refrigerant flows through the heat exchanger, the refrigerant may encounter resistance, such as from friction between the refrigerant and the inner surfaces of ports, which reduces the pressure of the refrigerant flowing through the heat exchanger. As a result, the flow rate of the refrigerant decreases as the refrigerant is directed through the lengthof the first and second microchannel tubes,.

In some embodiments, it may be desirable to reduce the pressure drop along the lengthof the first and second microchannel tubes,in order to increase a flow rate at which the refrigerant flows through the heat exchanger. For example, a geometry of the portsmay be selected to enable a reduction in the pressure drop of the refrigerant. In particular, a diameterof the portsmay be increased to reduce friction between the refrigerant and the port, thereby reducing the pressure drop of the refrigerant flowing through the ports. In additional or alternative embodiments, a shape of each portwithin each microchannel may also be selected to achieve a desired pressure drop. Thus, althoughillustrates each portas including a generally circular cross section, it should be understood that the portsmay be any other suitable shape, such as a rectangular or triangular shape. It should also be appreciated that different portsthroughout the heat exchangermay include different geometries from other portsof the heat exchanger. For example, a first portof the first microchannel tubemay include a first diameter and a first shape, a second portof the first microchannel tubemay include a second diameter and a second shape, and a third portof the second microchannel tubemay include a third diameter and a third shape.

Further, a position of the portswithin each microchannel tube,, such as a distancebetween adjacent ports, and/or a number of portsin a microchannel tube may also be selected to achieve a target performance of the heat exchanger. In particular, increasing the number of portsin a microchannel tube,may increase an amount of refrigerant directed through the heat exchangerand thus, may increase the amount of heat exchanged between the refrigerant and the fluid. Additionally, it should be understood that each microchannel tube,may include a different number of ports. Thus, althoughdepicts both the first and second microchannel tubes,as including four ports, the first microchannel tubemay include a different number of portsthan the second microchannel tube. To accommodate for the geometry of and number of ports, each microchannel tube,may include a particular length, tube height, and/or tube width. In some embodiments, increasing the length, the tube height, and/or the tube widthincreases an amount of heat exchanged between the refrigerant and the fluid by increasing a surface area of contact between the refrigerant and the fluid.

In certain embodiments, the set of finsmay also be configured to achieve a target performance of the heat exchanger. For example, certain first finsand/or second finsmay be positioned such that the set of finsincludes different anglesand/or angles. Additionally, althoughillustrates the set of finsas including a generally triangular profile, the set of finsmay include a different shape, such as a rectangular or arcuate shape. The geometry of the set of finsmay be selected to place the fluid passing across the heat exchangerin contact with an increased surface area of the set of fins. In this manner, an increased amount of heat may be exchanged between the fluid and the set of finsand, thus, between the fluid and the refrigerant.

It should also be understood that characteristics of the headermay also be selected to achieve a target performance of the heat exchanger. For example, the heightof the headermay be selected to accommodate a suitable number of microchannel tubes,disposed along the heightof the header. In this manner, a target amount of refrigerant and/or fluid may be directed through and/or across the heat exchanger. Additionally, a position of the header, a shape of the opening, and/or a size of the openingmay be selected to direct the refrigerant through the headerand/or through the first and second microchannel tubes,at a desired rate, pressure, velocity, temperature, and so forth. For example, the position of the header, the shape of the opening, and/or the size of the openingmay be selected to direct a target amount of refrigerant through the heat exchanger.

As described above, certain components of the heat exchangermay be modified to achieve a target performance of the heat exchanger. It should be appreciated that in addition to adjusting an amount of refrigerant and/or fluid that may be directed through and/or across the heat exchanger, modifying components of the heat exchangermay also adjust a cost of manufacturing the heat exchanger. For example, although increasing a surface area of contact between the fluid and the microchannel tubes,increases an amount of heat exchanged between the fluid and the refrigerant, increasing the surface area of contact may also increase manufacturing costs as a result of a greater amount of material used to create the heat exchanger. Thus, the size of components of the heat exchangermay be selected to balance performance of the heat exchangerwith a cost of manufacturing the heat exchanger.

In certain embodiments, the amount of heat exchanged between the fluid and the refrigerant is based on a distribution of a velocity of the fluid as the fluid is directed across the microchannel tubes,of the heat exchanger. For example, a speed at which the fluid is directed across each microchannel tube,may determine the amount of heat exchanged between the fluid and the refrigerant. In some embodiments, it may be desirable to have an improved distributed velocity profile of the fluid directed across the heat exchanger. That is, the heat exchangermay be designed such that the velocity of the fluid across each microchannel tube,along the respective lengthsis approximately the same (e.g., uniform) to enable the amount of heat transferred between the fluid and the refrigerant to be approximately the same across each respective length. In heat exchangersthat include a plurality of microchannel tubes,, the velocity profile of the fluid at certain portions of the heat exchangermay not be desirable due to an orientation of the microchannel tubes,and/or the set of finsrelative to a flow of the fluid. However, selecting a particular position of certain fins may produce an improved distributed velocity profile of the fluid across the heat exchangerto improve heat transfer efficiency of the heat exchanger.

is a side view of an embodiment of the heat exchanger, which may enable and generate an improved distributed velocity profile of fluid flowing across the heat exchanger. For instance, the heat exchangerincludes a first section, a second section, and a third sectionthat may cooperatively span the heightof the header. As shown in, refrigerant is directed into an inletof the header(e.g., a first header) of the heat exchangerin a direction, such as via tubing fluidly coupled to the inlet. A portion of the refrigerant may then be directed through a first set of coils(e.g., microchannel coils) of the first sectionin a direction, and a remaining portion of the refrigerant may be directed through a second set of coils(e.g., microchannel coils) of the second sectionin the direction. In both the first sectionand the second section, the refrigerant may flow through the first set of coilsand the second set of coils, respectively, along the lengthin the directionuntil the refrigerant reaches another header(e.g., a second header) of the heat exchanger. In the header, the refrigerant from both the first and second sections,may be combined and directed in a directionto the third section, where the refrigerant may be directed through a third set of coils(e.g., microchannel coils) in a directionopposite the direction. After flowing through the third set of coils, the refrigerant may exit the heat exchangerthrough an outletof the headerin the direction. Meanwhile, the fluid (e.g., the ambient airdirected by a fan) may be directed across the heat exchangerin the directionto flow across the first section, the second section, and the third sectionand therefore across the first, second, and third sets of coils,, and, respectively. In this manner, the heat exchangerfunctions as a two pass heat exchanger configured to direct the refrigerant flow through the third set of coilsto further exchange heat between the refrigerant and the fluid after directing the refrigerant through the first set of coilsand the second set of coils.

For clarity and discussion purposes, the first, second, and third sections,,are each depicted as including two coils of the respective first, second, and third sets of coils,, and. It should be understood that, as described herein, each set of coils includes a plurality of microchannel tubes, where adjacent tubes in each set include a set of fins (e.g., set of fins) disposed therebetween. In some embodiments, the first set of coilsincludes a first set of fins, the second set of coilsincludes a second set of fins, and the third set of coilsincludes a third set of fins. It should be appreciated that the first, second, and third sections,,may each include any suitable number of coils and, thus, may include any suitable number of microchannel tubes and corresponding sets of fins.

Additionally, each set of fins,,may include a fin density, or a number of fins within a certain length of the corresponding set of coils, such as the length. In certain embodiments, the selected fin density may impact an amount of heat exchanged between the refrigerant and the fluid (e.g., within the respective section). For example, a higher fin density increases an amount of surface area that the fluid contacts as it crosses the corresponding set of coils, and thus, may result in a greater amount of heat exchanged between the fluid and the refrigerant. Additionally, a higher fin density may decrease an amount of spacebetween the set of fins through which the fluid may flow. In some embodiments, the distancebetween each microchannel tube of the respective sets of coils,, andmay still remain the same. Thus, increasing the fin density while maintaining the same distancemay result in an increase of the angleand/or the angle, and decreasing the fin density while maintaining the same distancemay result in a decrease of the angleand/or the angle. As such, increasing the fin density while maintaining the same distancebetween adjacent microchannel tubes may decrease the amount of space, and decreasing the fin density while maintaining the same distancebetween adjacent microchannel tubes may increase the amount of space.

In some cases, the velocity of the fluid increases as a size of the spacedecreases, which may also affect the amount of heat exchanged between the refrigerant and the fluid. In some embodiments, the resulting velocity of the fluid may not be desirable across the heightof heat exchanger. Particularly, if each set of fins,,of each set of coils,, andincludes a similar fin density, the velocity of the fluid may be concentrated near a middle portionof the lengthof the heat exchanger. In other words, a velocity of the fluid proximate to the headerand/or the headermay be lower than a velocity of the fluid at the middle portionbetween the headerand the header.

In certain embodiments, it may be desirable for the fluid to have a particular velocity profile along the lengthof the heat exchanger. To create the desired velocity profile and flow of fluid across the heat exchanger, the fin density of each respective set of coils,, andmay be different from one another. By adjusting the fin density of the respective sets of coils,, and, the flow of fluid through the different sections,,of the heat exchangermay be improved.

It should be appreciated that the respective fin densities of the first, second, and third sections,,may be based at least in part on the respective locations of the sections,,along the heightand/or based at least in part on the respective heights of the sections,,. For example, the first sectionmay be positioned above the second sectionwith respect to the heightand may include a first length or heightthat is greater than a second length or heightof the second section. The second sectionmay be positioned above the third sectionwith respect to the height, and the second heightof the second sectionmay be greater than a third length or heightof the third section. As an example, the first heightof the first sectionmay be 50-55 centimeters (e.g., 19-22 inches), the second heightof the second sectionmay be 48-52 centimeters (e.g., 18-21 inches), and the third heightof the third sectionmay be 33-37 centimeters (e.g., 13-15 inches). In certain embodiments, the heights,,of the respective sections,,may be a percentage of one another. For example, the third heightof the third sectionmay be 65%-75% of the second heightof the second section, and the second sectionmay be 90-95% of the first heightof the first section.

In some embodiments, the fin density of the first set of coilsmay be greater than the fin density of the second set of coils, and the fin density of the second set of coilsmay be greater than the fin density of the third set of coilsto produce an improved velocity profile of fluid across the heat exchanger. For example, the fin density of the first set of coilsmay be 8-10 fins/centimeter (e.g., 20-25 fins/inch), the fin density of the second set of coilsmay be 7-9 fins/centimeter (e.g., 17-23 fins/inch), and the fin density of the third set of coilsmay be 5-7 fins/centimeter (e.g., 14-18 fins/inch). The fin density of each set of coils,,may also be selected as a percentage of one another. In one instance, the fin density of the third set of coilsmay be 65-75% of the fin density of the second set of coils, and the fin density of the second set of coilsmay be 85%-90% of the fin density of the first set of coils. Moreover, the fin density of each set of coils,,may also be determined by a ratio of the respective height,,. That is, the ratio of the first heightof the first sectionand the fin density of the first set of coilsmay be 0.9-0.95, the ratio of the second heightof the second sectionand the fin density of the second set of coilsmay be 0.9-1, and the ratio of the third heightof the third sectionand the fin density of the third set of coilsmay be 0.85-0.9. In this manner, the fluid may be directed across the first sectionat a higher velocity than across the second section, and the fluid may be directed across the second sectionat a higher velocity than across the third section. In further embodiments, the fin density of each set of coils,,may additionally or alternatively be based on another parameter, such as a distance between the set of coils,,and/or parameters of the fanthat directs the fluid across the heat exchanger. For instance, the fin densities may be based on a flowrate of fluid directed across the respective sets of coils,,via the fan. In the illustrated embodiment, the fanis positioned proximate to the first sectionsuch that the first sectionmay receive a greater flow rate of air relative to that of the sections,. As such, the first set of coilsmay have a higher fin density that is selected based on the greater flow rate of air directed across the first set of coils.

In general, the fin densities of different sets of coils,,of the heat exchangermay be different from one another and may be determined based at least in part on the location of the set of coils,,along the heightof the heat exchanger, along the lengthof the set of coils,,, a desired velocity of the fluid across the set of coils,,, a desired distribution of velocity of the fluid across the heat exchanger, and/or any other property of the sets of coils and/or operation of the heat exchanger.

In some embodiments, in order to select or modify a fin density, a fin lengthmay be adjusted between the sections,,of the heat exchanger. For example, the fin lengthmay be increased to increase the distancebetween coils and expanding the spacebetween the fins. As such, the velocity of fluid across the coils having an increased fin lengthis increased. In additional or alternative embodiments, changing the angles,while maintaining the same distancebetween coils, also adjusts the fin length. That is, the angles,and the fin lengthare adjusted to maintain the same distancebetween the microchannel tubes.

In the illustrated embodiment, each set of coils,,has substantially the same distancebetween the respective coils. However, each set of coils,,may include respective sets of fins having different fin lengthsand oriented at different angles,such that the fin density of the first set of coilsis greater than the fin density of the second set of coils, and the fin density of the second set of coilsis greater than the fin density of the third set of coils. For instance, a first fin lengthA of each fin of the first set of finsmay be less than a second fin lengthB of each fin of the second set of fins. Additionally, the second fin lengthB of each fin of the second set of finsmay be less than a third fin lengthC of each fin of the third set of fins. Accordingly, first anglesA,A between the fins of the first set of finsmay be greater than second anglesB,B between the fins of the second set of fins. Furthermore, the second anglesB,B between the fins of the second set of finsmay be greater than third anglesC,C between the fins of the third set of fins. In additional or alternative embodiments, as described above, the distancesmay also be different for the different sets of coils,,to vary the fin densities of the sets of coils,,relative to one another. For example, a first distanceA of the first set of coilsmay be less than a second distanceB of the second set of coils, and the second distanceB of the second set of coilsmay be less than a third distanceC of the third set of coils.

While this disclosure primarily discusses modification and selection of the fin density between sets of coils of different sections,,of the heat exchanger, it should also be understood that the fin density may vary along the lengthof the same set of coils,,. For example, a fin density of the first set of coilsproximate to the headermay be different than a fin density of the first set of coilsproximate to the header. Further, different sets of coils of the same section may include different fin densities. Further still, any combination of the aforementioned orientation or arrangement of the fins may be implemented to adjust the distribution of the velocity of the fluid flowing across the heat exchanger.

It should be appreciated that, althoughillustrates the heat exchangerin a particular arrangement, other configurations of the heat exchangermay also be utilized. For example, the heat exchangermay include additional sections and/or additional headers to direct the refrigerant through additional sets of coils before exiting the heat exchanger. Moreover, the heat exchangermay be configured to change directions of the flow of refrigerant through any of the sets of coils and/or direct the refrigerant in different directions than depicted in. Additionally or alternatively, the heat exchangermay be modified to include a different shape than depicted in.