WO2009076623A1

WO2009076623A1 - Hvac&r system with individualized flow control

Info

Publication number: WO2009076623A1
Application number: PCT/US2008/086652
Authority: WO
Inventors: Jeffrey Lee Tucker; Jeremiah Marshall Horn; Jeffrey Norris Nichols; Thomas John Martin; Gregory Ralph Harrod; Kenneth E. Hickman
Original assignee: Johnson Controls Technology Company
Priority date: 2007-12-13
Filing date: 2008-12-12
Publication date: 2009-06-18
Also published as: US20100251742A1; WO2009076628A2; WO2009076628A3

Abstract

An HVAC&R system is disclosed that utilizes energy-efficient valving. The valving controls the 'flow of refrigerant and may be adapted for evaporator or condenser applications, on both AC systems and heat pumps (as well as chillers and other refrigeration systems). In some configurations, the valving provides individualized control of flow through individual coils or groups of coils for improved control of evaporation, condensation, and so forth. A distributor (164) incorporating the valving (190) may be formed, and interfaced with sensors and a controller in a closed-loop manner. In other configurations, the valving may assist in improving operation of reversing valves, compressors, and so forth.

Description

HVAC&R SYSTEM WΓΓH INDIVIDUALIZED FLOW CONTROL

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from and the benefit of U.S. Provisional Application Serial No. 61/013,364, entitled "HVAC&R SYSTEM EMPLOYING UNIQUE VALVING," filed December 13, 2007, which is hereby incorporated by reference.

BACKGROUND

[0002] The present invention relates generally to heating, ventilating, air conditioning and refrigeration systems, and more particularly to techniques for controlling fluid flow in such systems.

[0003] A wide range of applications exist for heating, ventilating, air conditioning and refrigeration (HVAC&R) systems. For example, residential, light commercial, commercial and industrial systems are used to control temperatures and air quality in residences and buildings. Such systems often are dedicated to either heating or cooling, although systems are common that perform both of these functions. Very generally, these systems operate by implementing a thermal cycle in which fluids are heated and cooled to provide the desired temperature in a controlled space, typically the inside of a residence or building. Similar systems are used for vehicle heating and cooling, and as well as for general refrigeration.

[0004] Controlled fluids within such systems are typically confined with enclosed circuits and include various refrigerants. Refrigerants are specifically formulated to undergo phase changes within the normal operating temperatures and pressures of the systems so that considerable quantities of heat can be exchanged by virtue of the latent heat of vaporization of the circulated refrigerant. In most such systems, for example, the refrigerant is evaporated in one heat exchanger to draw heat from air circulating through the heat exchanger for cooling purposes. Conversely, the refrigerant is then condensed in a different heat exchanger to release heat from the refrigerant and thereby heat an air stream. Depending upon whether the evaporating heat exchanger and condensing heat exchanger are inside of the controlled space or outside of the controlled space, the system will function to heat or cool the air within the space.

[0005] A number of locations in such systems are subject to careful control of the flow of circulating refrigerant. For example, a distributor is commonly provided upstream of the evaporating heat exchanger to form separate paths for refrigerant flowing through that device. Commonly employed distributors are, however, quite simple and generally serve only for distribution purposes.

[0006] While such fluid control devices are useful and offer highly efficient and functional systems, further improvement is desired. For example, it would be desirable to allow for a higher degree of control of individual circuits, and control of existing circuits in a way that would use less energy or provide a more cost-effective solution.

SUMMARY

[0007] The present invention relates to a heating, ventilating, air conditioning, or refrigeration system with a plurality of heat exchanger flow paths configured to circulate a fluid through one or more heat exchanger tubes. The system includes control valving configured to simultaneously and independently regulate flow of the fluid through each of the heat exchanger flow paths.

[0008] The present invention also relates to a distributor with a plurality of flow passages configured to fluidly connect to flow paths of a heat exchanger. The distributor includes valves disposed in each of the plurality of flow passages that are configured to simultaneously regulate flow through each of the plurality of flow passages.

[0009] The present invention further relates to methods employing the system and/or the distributor. DRAWINGS

[0010] FIGURE 1 is an illustration of an exemplary residential air conditioning or heat pump system of the type that might employ valving arrangements for individualized flow control.

[0011] FIGURE 2 is a partially exploded view of the outside unit of the system of FIGURE 1, with an upper assembly lifted to expose certain components of the system.

[0012] FIGURE 3 is an illustration of an exemplary commercial or industrial HVAC&R system that employs a chiller and air handlers to cool a building and that also may employ valving arrangements for individualized flow control.

[0013] FIGURE 4 is a diagrammatical overview of an exemplary air conditioning system that may employ individualized flow control.

[0014] FIGURE 5 is a diagrammatical overview of an exemplary heat pump system that also may employ individualized flow control.

[0015] FIGURE 6 is a diagrammatical representation of an exemplary individualized, closed-loop control scheme for regulating the flow of refrigerant through parallel heat exchange paths.

[0016] FIGURE 7 is a somewhat more detailed view of an arrangement of the type shown in FIGURE 6.

[0017] FIGURE 8 is another diagrammatical representation of an individualized flow path heat exchanger system made based upon a modular design.

[0018] FIGURE 9 is a diagrammatical illustration of yet another individualized flow control technique. [0019] FIGURE 10 is a perspective diagrammatical view of an exemplary heat exchanger and distributor arrangement for providing individually controlled flow paths through the heat exchanger.

[0020] FIGURE 11 is a sectional view through an exemplary distributor of the type shown in FIGURE 10.

[0021] FIGURE 12 is an exploded sectional view of the distributor of FIGURE 11.

DETAILED DESCRIPTION

[0022] FIGURES 1 to 3 depict exemplary applications for circuiting configurations employing unique valving for individualized flow control. The systems may include heat exchangers fluidly coupled to valving and/or distributors that provide individualized flow control through heat exchanger tubes or groups of tubes. In certain embodiments, the valving may include a plurality of valves, each coupled to flow paths through one or more heat exchangers. Such systems, in general, may be applied in a wide range of settings, both within the HVAC&R field and outside of that field. In presently contemplated applications, however, the invention 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 invention may be used in industrial applications, where appropriate, for basic refrigeration and heating of various fluids.

[0023] FIGURE 1 illustrates a residential heating and cooling system. In general, a residence 10 will include refrigerant conduits 12 that operatively couple an indoor unit 14 to an outdoor unit 16. Indoor unit 14 may be positioned in a utility room, an attic, a basement, or other location. Outdoor unit 16 is typically situated adjacent to a side of residence 10 and is covered by a shroud to protect the system components and to prevent leaves and other contaminants from entering the unit. Refrigerant conduits 12 transfer refrigerant between indoor unit 14 and outdoor unit 16, typically transferring primarily liquid refrigerant in one direction and primarily vaporized refrigerant in an opposite direction. [0024] When the system shown in FIGURE 1 is operating as an air conditioner, a coil in outdoor unit 16 serves as a condenser for recondensing vaporized refrigerant flowing from indoor unit 14 to outdoor unit 16 via one of the refrigerant conduits 12. In these applications, a coil of the indoor unit, designated by the reference numeral 18, serves as an evaporator coil. Evaporator coil 18 receives liquid refrigerant (which may be expanded by an expansion device, not shown) and evaporates the refrigerant before returning it to outdoor unit 16.

[0025] Outdoor unit 16 draws in environmental air through its sides as indicated by the arrows directed to the sides of the unit, forces the air through the outer unit coil by a means of a fan (not shown), and expels the air as indicated by the arrows above the outdoor unit. When operating as an air conditioner, the air is heated by the condenser coil within the outdoor unit and exits the top of the unit at a temperature higher than when it entered the sides. Air is blown over indoor coil 18 and is then circulated through residence 10 by means of ductwork 20, as indicated by the arrows entering and exiting ductwork 20. The overall system operates to maintain a desired temperature as set by a thermostat 22. When the temperature sensed inside the residence is higher than the set point on the thermostat (plus a small amount), the air conditioner will become operative to refrigerate additional air for circulation through the residence. When the temperature reaches the set point (minus a small amount), the unit will stop the refrigeration cycle temporarily.

[0026] When the unit in FIGURE 1 operates as a heat pump, the roles of the coils are simply reversed. That is, the coil of outdoor unit 16 will serve as an evaporator to evaporate refrigerant and thereby cool air entering outdoor unit 16 as the air passes over the outdoor unit coil. Indoor coil 18 will receive a stream of air blown over it and will heat the air by condensing a refrigerant.

[0027] FIGURE 2 illustrates a partially exploded view of one of the units shown in FIGURE 1, in this case outdoor unit 16. In general, the unit may be thought of as including an upper assembly 24 made up of a shroud, a fan assembly, a fan drive motor, and so forth. In the illustration of FIGURE 2, the fan and fan drive motor are not visible because they are hidden by the surrounding shroud. An outdoor coil 26 is housed within this shroud and is generally deposed to surround or at least partially surround other system components, such as a compressor, an expansion device, a control circuit.

[0028] FIGURE 3 illustrates another exemplary application, in this case an HVAC&R system for building environmental management. A building 28 is cooled by a system that includes a chiller 30, which is typically disposed on or near the building, or in an equipment room or basement. Chiller 30 is an air-cooled device that implements a refrigeration cycle to cool water. The water is circulated to building 28 through water conduits 32. The water conduits are routed to air handlers 34 at individual floors or sections of the building. The air handlers are also coupled to ductwork 36 that is adapted to blow air from an outside intake 38.

[0029] Chiller 30, which includes heat exchangers for both evaporating and condensing a refrigerant as described above, cools water that is circulated to the air handlers. Air blown over additional coils that receive the water in the air handlers causes the water to increase in temperature and the circulated air to decrease in temperature. The cooled air is then routed to various locations in the building via additional ductwork. Ultimately, distribution of the air is routed to diffusers that deliver the cooled air to offices, apartments, hallways, and any other interior spaces within the building. In many applications, thermostats or other command devices (not shown in FIGURE 3) will serve to control the flow of air through and from the individual air handlers and ductwork to maintain desired temperatures at various locations in the structure.

[0030] FIGURE 4 illustrates an air conditioning system 40, which may employ multichannel tube heat exchangers. Refrigerant flows through system 40 within closed refrigeration loop 42. The refrigerant may be any fluid that absorbs and extracts heat. For example, the refrigerant may be hydrofluorocarbon (HFC) based R- 410A, R-407, or R- 134a, or it may be carbon dioxide (R-744) or ammonia (R-717). Air conditioning system 40 includes control devices 44 that enable the system to cool an environment to a prescribed temperature. [0031] System 40 cools an environment by cycling refrigerant within closed refrigeration loop 42 through a condenser 46, a compressor 48, an expansion device 50, and an evaporator 52. The refrigerant enters condenser 46 as a high pressure and temperature vapor and flows through the multichannel tubes of the condenser. A fan 54, which is driven by a motor 56, draws air across the multichannel tubes. The fan may push or pull air across the tubes. As the air flows across the tubes, heat transfers from the refrigerant vapor to the air, producing heated air 58 and causing the refrigerant vapor to condense into a liquid. The liquid refrigerant then flows into an expansion device 50 where the refrigerant expands to become a low pressure and temperature liquid. Typically, expansion device 50 will be a thermal expansion valve (TXV); however, according to other exemplary embodiments, the expansion device may be an orifice or a capillary tube. After the refrigerant exits the expansion device, some vapor refrigerant may be present in addition to the liquid refrigerant.

[0032] From expansion device 50, the refrigerant enters evaporator 52 and flows through the evaporator multichannel tubes. A fan 60, which is driven by a motor 62, draws air across the multichannel tubes. As the air flows across the tubes, heat transfers from the air to the refrigerant liquid, producing cooled air 64 and causing the refrigerant liquid to boil into a vapor. According to certain embodiments, the fan may be replaced by a pump that draws fluid through the evaporator. The evaporator may be a shell- and- tube heat exchanger, brazed plate heat exchanger, or other suitable heat exchanger.

[0033] The refrigerant then flows to compressor 48 as a low pressure and temperature vapor. Compressor 48 reduces the volume available for the refrigerant vapor, consequently, increasing the pressure and temperature of the vapor refrigerant. The compressor may be any suitable compressor such as a screw compressor, reciprocating compressor, rotary compressor, swing link compressor, scroll compressor, or turbine compressor. Compressor 48 is driven by a motor 66 that receives power from a variable speed drive (VSD) or a direct AC or DC power source. According to an exemplary embodiment, motor 66 receives fixed line voltage and frequency from an AC power source although in certain applications the motor may be driven by a variable voltage or frequency drive. The motor may be a switched reluctance (SR) motor, an induction motor, an electronically commutated permanent magnet motor (ECM), or any other suitable motor type. The refrigerant exits compressor 48 as a high temperature and pressure vapor that is ready to enter the condenser and begin the refrigeration cycle again.

[0034] The control devices 44, which include control circuitry 68, an input device 70, and a temperature sensor 72, govern the operation of the refrigeration cycle. Control circuitry 68 is coupled to the motors 56, 62, and 66 that drive condenser fan 54, evaporator fan 60, and compressor 48, respectively. Control circuitry 68 uses information received from input device 70 and sensor 72 to determine when to operate the motors 56, 62, and 66 that drive the air conditioning system. In certain applications, the input device may be a conventional thermostat. However, the input device is not limited to thermostats, and more generally, any source of a fixed or changing set point may be employed. These may include local or remote command devices, computer systems and processors, and mechanical, electrical and electromechanical devices that manually or automatically set a temperature-related signal that the system receives. For example, in a residential air conditioning system, the input device may be a programmable 24-volt thermostat that provides a temperature set point to the control circuitry. Sensor 72 determines the ambient air temperature and provides the temperature to control circuitry 68. Control circuitry 68 then compares the temperature received from the sensor to the temperature set point received from the input device. If the temperature is higher than the set point, control circuitry 68 may turn on motors 56, 62, and 66 to run air conditioning system 40. The control circuitry may execute hardware or software control algorithms to regulate the air conditioning system. According to exemplary embodiments, the control circuitry may include an analog to digital (A/D) converter, a microprocessor, a non-volatile memory, and an interface board. Other devices may, of course, be included in the system, such as additional pressure and/or temperature transducers or switches that sense temperatures and pressures of the refrigerant, the heat exchangers, the inlet and outlet air, and so forth.

[0035] FIGURE 5 illustrates a heat pump system 74 that may employ multichannel tube heat exchangers. Because the heat pump may be used for both heating and cooling, refrigerant flows through a reversible refrigeration/heating loop 76. The refrigerant may be any fluid that absorbs and extracts heat. The heating and cooling operations are regulated by control devices 78.

[0036] Heat pump system 74 includes an outside coil 80 and an inside coil 82 that both operate as heat exchangers. The coils may function either as an evaporator or a condenser depending on the heat pump operation mode. For example, when heat pump system 74 is operating in cooling (or "AC") mode, outside coil 80 functions as a condenser, releasing heat to the outside air, while inside coil 82 functions as an evaporator, absorbing heat from the inside air. When heat pump system 74 is operating in heating mode, outside coil 80 functions as an evaporator, absorbing heat from the outside air, while inside coil 82 functions as a condenser, releasing heat to the inside air. A reversing valve 84 is positioned on reversible loop 76 between the coils to control the direction of refrigerant flow and thereby to switch the heat pump between heating mode and cooling mode.

[0037] Heat pump system 74 also includes two metering devices 86 and 88 for decreasing the pressure and temperature of the refrigerant before it enters the evaporator. The metering devices also regulate the refrigerant flow entering the evaporator so that the amount of refrigerant entering the evaporator equals, or approximately equals, the amount of refrigerant exiting the evaporator. The metering device used depends on the heat pump operation mode. For example, when heat pump system 74 is operating in cooling mode, refrigerant bypasses metering device 86 and flows through metering device 88 before entering inside coil 82, which acts as an evaporator. In another example, when heat pump system 74 is operating in heating mode, refrigerant bypasses metering device 88 and flows through metering device 86 before entering outside coil 80, which acts as an evaporator. According to other exemplary embodiments, a single metering device may be used for both heating mode and cooling mode. The metering devices typically are thermal expansion valves (TXV), but also may be orifices or capillary tubes.

[0038] The refrigerant enters the evaporator, which is outside coil 80 in heating mode and inside coil 82 in cooling mode, as a low temperature and pressure liquid. Some vapor refrigerant also may be present as a result of the expansion process that occurs in metering device 86 or 88. The refrigerant flows through multichannel tubes in the evaporator and absorbs heat from the air changing the refrigerant into a vapor. In cooling mode, the indoor air flowing across the multichannel tubes also may be dehumidified. The moisture from the air may condense on the outer surface of the multichannel tubes and consequently be removed from the air.

[0039] After exiting the evaporator, the refrigerant passes through reversing valve 84 and into a compressor 90. Compressor 90 decreases the volume of the refrigerant vapor, thereby, increasing the temperature and pressure of the vapor. The compressor may be any suitable compressor such as a screw compressor, reciprocating compressor, rotary compressor, swing link compressor, scroll compressor, or turbine compressor.

[0040] From compressor 90, the increased temperature and pressure vapor refrigerant flows into a condenser, the location of which is determined by the heat pump mode. In cooling mode, the refrigerant flows into outside coil 80 (acting as a condenser). A fan 92, which is powered by a motor 94, draws air across the multichannel tubes containing refrigerant vapor. According to certain exemplary embodiments, the fan may be replaced by a pump that draws fluid across the multichannel tubes. The heat from the refrigerant is transferred to the outside air causing the refrigerant to condense into a liquid. In heating mode, the refrigerant flows into inside coil 82 (acting as a condenser). A fan 96, which is powered by a motor 98, draws air across the multichannel tubes containing refrigerant vapor. The heat from the refrigerant is transferred to the inside air causing the refrigerant to condense into a liquid. After exiting the condenser, the refrigerant flows through the metering device (86 in heating mode and 88 in cooling mode) and returns to the evaporator (outside coil 80 in heating mode and inside coil 82 in cooling mode) where the process begins again.

[0041] In both heating and cooling modes, a motor 100 drives compressor 90 and circulates refrigerant through reversible refrigeration/heating loop 76. The motor may receive power either directly from an AC or DC power source or from a variable speed drive (VSD). The motor may be a switched reluctance (SR) motor, an induction motor, an electronically commutated permanent magnet motor (ECM), or any other suitable motor type.

[0042] The operation of motor 100 is controlled by control circuitry 102. Control circuitry 102 receives information from an input device 104 and sensors 106, 108, and 110 and uses the information to control the operation of heat pump system 74 in both cooling mode and heating mode. For example, in cooling mode, input device 104 provides a temperature set point to control circuitry 102. Sensor 110 measures the ambient indoor air temperature and provides it to control circuitry 102. Control circuitry 102 then compares the air temperature to the temperature set point and engages compressor motor 100 and fan motors 94 and 98 to run the cooling system if the air temperature is above the temperature set point. In heating mode, control circuitry 102 compares the air temperature from sensor 110 to the temperature set point from input device 104 and engages motors 94, 98, and 100 to run the heating system if the air temperature is below the temperature set point.

[0043] Control circuitry 102 also uses information received from input device 104 to switch heat pump system 74 between heating mode and cooling mode. For example, if input device 104 is set to cooling mode, control circuitry 102 will send a signal to a solenoid 112 to place reversing valve 84 in an air conditioning position 114. Consequently, the refrigerant will flow through reversible loop 76 as follows: the refrigerant exits compressor 90, is condensed in outside coil 80, is expanded by metering device 88, and is evaporated by inside coil 82. If the input device is set to heating mode, control circuitry 102 will send a signal to solenoid 112 to place reversing valve 84 in a heat pump position 116. Consequently, the refrigerant will flow through the reversible loop 76 as follows: the refrigerant exits compressor 90, is condensed in inside coil 82, is expanded by metering device 86, and is evaporated by outside coil 80.

[0044] The control circuitry may execute hardware or software control algorithms to regulate heat pump system 74. According to exemplary embodiments, the control circuitry may include an analog to digital (AfD) converter, a microprocessor, a nonvolatile memory, and an interface board. [0045] The control circuitry also may initiate a defrost cycle when the system is operating in heating mode. When the outdoor temperature approaches freezing, moisture in the outside air that is directed over outside coil 80 may condense and freeze on the coil. Sensor 106 measures the outside air temperature, and sensor 108 measures the temperature of outside coil 80. These sensors provide the temperature information to the control circuitry which determines when to initiate a defrost cycle. For example, if either sensor 106 or 108 provides a temperature below freezing to the control circuitry, system 74 may be placed in defrost mode. In defrost mode, solenoid 112 is actuated to place reversing valve 84 in air conditioning position 114, and motor 94 is shut off to discontinue air flow over the multichannel tubes. System 74 then operates in cooling mode until the increased temperature and pressure refrigerant flowing through outside coil 80 defrosts the coil. Once sensor 108 detects that coil 80 is defrosted, control circuitry 102 returns the reversing valve 84 to heat pump position 116. As will be appreciated by those skilled in the art, the defrost cycle can be set to occur at many different time and temperature combinations.

[0046] It should be noted that while reference is made in the present discussion to "multichannel" tubes used in HVAC&R systems, other types and configurations of tubes may be used in conjunction with certain embodiments described herein, particularly those relating to valving and the control of flow to enhance system performance.

[0047] Flow through either or both of the heat exchangers in the systems described above may be performed in a closed-loop and individualized manner as illustrated diagrammatically in FIGURE 6. In the embodiment illustrated, control valving 118 provides flow to a multiple-path heat exchanger 120 that may serve as an evaporator or as a condenser. The heat exchanger receives individually controlled flow as indicated by reference numeral 122 in FIGURE 6 that is directed through individual flow paths within the heat exchanger. In practice, the flow paths may include a group of tubes, or as few as a single tube. In certain embodiments, each tube group may include approximately 1 to 90 tubes, or more specifically, each tube group may include approximately 1 to 10 tubes. However, in other embodiments, any number of tubes may be included within a group, and the number of tubes within each tube group may vary. Moreover, the tubes may be of various types, such as multichannel tubes, conventional copper or aluminum tubing, and so forth.

[0048] As discussed in greater detail below, the control valving 118 may include small individually controlled valves that regulate the flow through each of the flow paths of the heat exchanger. In certain embodiments, the small individually controlled valves may include pneumatic or hydraulic silicon valves with orifices ranging from approximately 0.01 mm to 1.75 mm. However, in other embodiments, the valves may be constructed of other suitable materials and may have orifices of any size. Further, the valves may allow for proportional control, on/off control, and the like. The system also includes one or more sensors as indicated by reference numeral 124, which may include sensors for both temperature and pressure. In certain embodiments, individual sensors may be provided for each group of tubes, or even for individual tubes of the heat exchanger. In certain other embodiments, a single temperature and pressure sensor may be provided. The number of sensors may be varied in specific embodiments based upon the degree of individualized controlled desired for the flow of refrigerant.

[0049] The sensors are coupled to control circuitry 126 for directing signals representative of the sensed parameters to the control circuitry. Such control circuitry may include any suitable processors, memory, computers, field programmable gate arrays, and so forth. More generally, the control circuitry may be independent of or the same as the control circuitry used for regulating the overall operation of the system as described above. In certain embodiments, specific and separate control circuitry may be provided (e.g., local to the associated heat exchanger) that can nevertheless be interfaced with the overall control circuitry, such that control circuitry 126 receives the sensed parameter signals and regulates operation of the control valving 118 in a closed-loop manner. In operation, then, the control valving 118 is commanded to open or close flow paths (or to meter flow) to circulate refrigerant through the heat exchanger, with air, as indicated by arrow 128 being drawn or forced through the heat exchanger to heat or cool the air as described above. [0050] FIGURE 7 illustrates a somewhat more detailed view of one embodiment of the individualized control arrangement. In the embodiment shown in FIGURE 7, individual control valves 130 are provided in line with the individually controlled flow paths 122. Each valve is coupled to the control circuitry 126. In particular, the individual control valves 130 are provided upstream of the heat exchanger to regulate the flow of fluid through the heat exchanger. Individual sensors 132 may also be provided along each of the flow paths for closed-loop control of the respective valve. In certain embodiments, the individual sensors may sense parameters, such as temperature or pressure, that are internal to or external to the flow paths. In operation, fluid is received in a first manifold 134 and circulates through the valves 130 and parallel flow paths of the heat exchanger to an opposite manifold 136. As will be appreciated by those skilled in the art, the manifolds and flow paths may be configured to provide multiple passes through the heat exchanger (e.g., from manifold 134 to manifold 136 and returning back to manifold 134). The control circuitry 126, then, receives signals from the sensors and causes the individual valves 130 to open and close to control flow through the heat exchanger based upon the sensed signals. The control circuitry will typically provide power and control signals to the valving via communication links 138. In certain embodiments, the communication links 138 may include wired, wireless, networked, and/or non-networked communication links.

[0051] In one presently contemplated application for this arrangement, an evaporator is designed with individualized flow paths that can be controlled by the control circuitry. The evaporator may be, for example, an indoor coil on an air conditioning unit or an outside coil on a heat pump (discussed in greater detail below). The control of distribution of refrigerant between the parallel flow paths enables the system to achieve proper control of each circuit based upon the pressure and temperature of the refrigerant, particularly the temperature of each individual flow path. That is, as will be appreciated by those skilled in the art, in an evaporator application, the flow paths serve to heat liquid refrigerant received by the heat exchanger, to force the refrigerant to undergo a phase change, and then, depending upon the system designed, to perform super heating of the refrigerant before exiting the heat exchanger. Because some tubes of the heat exchanger may evaporate the refrigerant more quickly than others, such passages may result in unnecessary super heating, with less heat being conveyed to the refrigerant than would be the case for evaporation alone (due to the significant difference between the sensible heat of the vaporized refrigerant and the latent heat of vaporization). Certain flow paths operating at higher pressures or temperatures, for example, could then be individually metered to limit flow, with flow being directed more to coils or fluid flow paths where additional evaporation may take place. As a result, the overall surface of the heat exchanger coil may be reduced while maintaining the same thermal transfer capacity, or improved thermal transfer capacity may be obtained with the same heat exchanger surface area. Similarly, variations in flow of the fluid in different flow paths of the heat exchanger could occur due to air flow, such as damage to the fins, different configurations of the fins, the presences of ice or moisture around the coils, fin density differences, blockages within the tubes, and so forth. The close-loop control allows for optimization through the various flow paths to minimize the impact of such variations on system performance. In general, it may be advantageous to ensure that sufficient thermal transfer occurs in evaporator applications such that no liquid exits the evaporator at all, thereby maximizing thermal transfer by virtue of phase change in the refrigerant.

[0052] As noted above, the individualized control of fluid flow through the heat exchanger flow paths can be performed on an individual tube basis, or on a group of tubes. In general, a balance will be struck between the quality of control desired, with generally superior or optimized control being provided with individual regulation of flow through individual flow paths each instrumented separately, and the cost of such control. Where component costs can be sufficiently reduced, for example, optimal control may be provided by individual valving on each individual flow tube which may also be equipped with its own sensors for closed-loop regulation. Acceptable compromises might include, however, grouping tubes together for full control and for sensing purposes. Moreover, any suitable devices may be utilized for regulating the control of fluid flow, with presently contemplated devices including small MEMS valves of the type commercially available from Microstaq Inc. of Austin, Texas. Such valves require very little energy for control purposes, and can regulate or meter flow based upon a simple control input from the control circuitry. [0053] The valving may also be controlled to provide for enhanced dehumidification of air circulated through evaporator coils. In particular, it has been recognized that even when additional cooling is not necessarily desired (as by an evaporator coil operating indoors in an AC system, or a heat pump system operating in AC mode), reducing the temperature of the indoor heat exchanger can force a reduction in the humidity or moisture level of the inside air (e.g., by causing condensation on the evaporator coils). In heretofore known systems, such dehumidification was typically performed by simply reducing the air flow through the system (e.g., by adjusting blower speed). The valving control of individual flow paths permits the system to force certain flow paths or circuits to flood or remain close to flooding (e.g., not evaporate liquid refrigerant introduced into them). In essence, the present technique may permit closed-loop flow control through individual flow paths so as to reduce superheating of refrigerant, thereby reducing the temperature of air passing through the heat exchanger and forcing a reduction in the humidity of the air. In certain embodiments, certain tubes may be more favored for such flooding or near flooding, such as lower tubes or tubes inside the stack or array.

[0054] One presently contemplated arrangement for grouping flow paths in a modular fashion is illustrated diagrammatically in FIGURE 8. As shown in this figure, modular units 140 and 142 and 144 may be pre-fabricated for assembly in a system, depending upon the thermal transfer capacity required. For example, the modular units may be designed for handling one ton of heat absorption capacity each (or some other standardized capacity) with additional units being added in a modular fashion depending upon the system needs. In this embodiment, each modular unit is itself a heat exchanger with parallel flow paths. Each of these modular heat exchangers includes at least one control valve 130 and its own pressure and temperature sensors 146 and 148, respectively. The modular units are designed to be plumbed simply to one another to form common inlet and exhaust manifolds. Moreover, the module units are designed for simple interfacing to control circuitry 126, such as by electrically coupling the individual sensors to the control circuitry along with the individual control valving. It should be noted that the control circuitry could also control multiple valves 130 for each of the modular heat exchanger units in a manner similar to that described above with reference to FIGURE 7.

[0055] FIGURE 9 is another exemplary configuration with multiple flow paths. As illustrated in this figure, commonly received refrigerant is distributed to two different heat exchangers 150 via individually controlled valving 152, 154 and 156. The valves may be similar to those described above, and would be controlled by associated control circuitry of the type described above. The valves serve to separate and distribute flow through the multiple heat exchangers in various flow paths, the inlets of which are illustrated in FIGURE 9 and represented by reference numerals 158 (for valve 152), 160 (for valve 154), and 162 (for valve 156). The arrangement may include more than two heat exchangers and additional circuits associated with individually controlled flow control valving.

[0056] In the foregoing embodiments, separate control valving is associated with one or more flow paths in the heat exchangers described. As illustrated in FIGURE 10, similar arrangements may be designed wherein the valving is disposed in a single distribution device, externally similar to conventional distributors, but in which individual control of fluid flow is implemented. In the embodiment shown in FIGURE 10, for example, a distributor 164 is provided for distributing flow through parallel flow paths of a heat exchanger 166. As will be appreciated by those skilled in the art, in a typical application the heat exchanger will serve as an evaporator such that the distributor receives liquid flow and distributes the liquid flow to individual sections of the heat exchanger. As described below, however, the distributor may be designed such that reverse flow is accommodated, such as when an indoor coil that serves as an evaporator in air conditioning mode of a heat pump is used as a condensing coil during heat pump mode operation.

[0057] In the embodiment shown in FIGURE 10, the heat exchanger 166 includes a first manifold 168 and second manifold 170 that are in fluid communication with heat exchanging tubes 172. As with previous embodiments, the system may be designed to provide multiple passes between the manifolds, such as by returning flow from manifold 170 back to manifold 168. However, for simplicity, a single pass heat exchanger is illustrated. The individual tubes 172 may be of any suitable design, such as multichannel tubes in which a plurality of parallel passageways are formed along the width of a generally flat tube, the passageways being in fluid communication with the interior volumes of the manifolds 168 and 170. Heat exchanging fins 174 are disposed between the tubes, and may be thermally and mechanically fixed to the tubes to aid in the transfer of heat between air streams flowing through the heat exchanger and the refrigerant flowing through the tubes.

[0058] Baffles 176 may be disposed in one or both manifolds, with the baffles illustrated in FIGURE 10 serving to isolate separate regions 178 of manifold 168. Refrigerant is then delivered to these regions and flows through tubes in fluid communication with the specific region to manifold 170. Each region is fed by a separate distribution conduit 180 leading from the distributor to the individual region of manifold 168.

[0059] A currently contemplated embodiment of a distributor of this type is illustrated in FIGURES 11 and 12. The distributor may be formed of any suitable materials and by any suitable methods, but presently contemplated methods include metal forming, rolling, drawing, molding, extrusion, brazing and similar operations on copper, copper alloys, brass, plastics, aluminum, aluminum alloys, and similar materials that are somewhat impervious to oxidation and deterioration in the HVAC&R environment. The distributor 164 generally includes an inlet conduit 182 for receiving fluid flow into a cap 184. The cap is coupled to a main housing 186 that is, in turn, fluid coupled to a distributor body 188. In operation, as described in greater detail below, fluid flows from the inlet conduit 182, through the main housing where it is distributed by individual valving, and to the distributor body 188 where individual flow lines 180 convey the fluid to individual conductors or fluid pathways in a heat exchanger.

[0060] Within the cap 184, and between the cap and the main housing, a check plate 190 is positioned. The check plate 190 fits within an upper volume 192 of the main housing and can move axially within this volume for controlling flow as described below. A valve array body 194 (see, FIGURE 12) is positioned within an interior volume 196 of the main housing and fits snuggly within the interior volume, being positioned by facets formed within the interior volume wall as best illustrated in FIGURE 12. Tight fluid sealed assembly of the device is maintained by a lower nut 198 which joins the distributor body 188 to the main housing 186, and by threaded connection between the cap 184 and the main housing 186.

[0061] The check plate 190 is formed with an upper stop surface 200 generally surrounding a plate-like base through which a fluid passage 202 is formed. A lower surface 204 forms a sealing surface for sealing against a corresponding surface within the main housing as described below.

[0062] Below the check plate, an interior volume of the valve array body is designed to receive fluid flow from the inlet conduit 182, through the check plate 190, and to deliver such flow to passages 208 formed around the periphery of the interior volume 206. Valves 210 are positioned within the valve array body, such as in the peripheral wall (the valve array body being made of a single or multiple elements designed to receive the valves and to provide the necessary sealing around them). Exit passages 212 are formed for communicating fluid released by the valves to individual flow paths of a heat exchanger. That is, fluid present within the interior volume 206 of the valve array body 194 can be stopped by each of the valves, or permitted to flow between the passages 208 and the exit passages 212. Selective operation of the individual valves is controlled by signals received from control circuitry as described above. Internal connections may be provided within the valve array body 194 for transmission of such control signals.

[0063] The main housing 186 includes a series of radially-disposed axial passages 214 around the inner volume 196 in which the valve array body 194 is disposed. The valve array body itself may be aligned with such passages by means of keys, facets, or any other feature. Valve-side inlets 216 are formed that permit fluid flow from the exit passages 212 of the valve array body to the radially disposed axial passages 214 during operation. Once fluid is introduced into each of the axial passages 214, then, the fluid is transmitted towards a bottom 218 of the main housing 186. [0064] The main housing 186 is positioned appropriately with respect to the distributor body 188 by means of a key feature 220 that receives and cooperates with a key 222. Various orientation- sensitive keys may be employed for this purpose. In general, this feature allows the radially-disposed axial passages 214 of the main housing to interface with, seal with and remain aligned with sealing surfaces 224 that surround each of the individual distribution conduits 180 that exit the assembly.

[0065] In operation, when the device receives fluid in the conduit 182, the fluid pressure forces the check plate 190 downwardly in the orientation shown in FIGURES 11 and 12, such that the lower sealing surface 204 seals against the upper surface of the axial passages 214 to seal these passages from fluid flow. Fluid is then forced to flow through passage 202 of the check plate and into the interior volume 206 of the valve array body 194. The individual valves may then regulate such flow, releasing regulated flow into respective axial passages 214 from which the fluid exits through respective distribution conduits 180. If flow is received in an opposite direction, that is, from the conduits 180 (e.g., for an interior coil of a heat pump operating in heat pump mode), the fluid flows from the distribution conduits 180, upwardly through the axial passages 214, moving the check plate 190 upwardly and enabling flow around the check plate, effectively bypassing the valves in an opposite direction. Fluid flow may then freely pass through the distributor assembly, exiting through the conduit 182.

[0066] It may also be noted that adaptations of the structures shown in FIGURES 11 and 12 may be envisaged to accommodate different system designs. For example, the main housing may be designed for more parallel flow paths than the actual heat exchanger may have. In this manner, more axial passages 214 may be provided than the number of individual valves in the valve array body 194. Certain of these passages in the valve array body may simply be plugged or the valve array body may be designed to simply provide the number of valves corresponding to the number of distribution conduits 180. The passages 214, then, not associated with a valve simply do not receive refrigerant flow. These passages will also be plugged at a lower end by the absence of a distribution conduit 180. In a presently contemplated embodiment, for example, eight regularly disposed passages 214 may be provided, with different valve array bodies providing for either eight parallel flow paths or four parallel flow paths, depending upon the number of valves present in the valve array body.

[0067] While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

CLAIMS:

1. A heating, ventilating, air conditioning, or refrigeration system comprising: a plurality of heat exchanger flow paths configured to circulate a fluid through one or more heat exchanger tubes; and control valving configured to simultaneously and independently regulate flow of the fluid through each of the heat exchanger flow paths.

2. The system of claim 1, wherein the each of the plurality of heat exchanger flow paths comprises a tube or a group of tubes within a heat exchanger.

3. The system of claim 1, wherein each of the plurality of heat exchanger flow paths comprises a modular pre-fabricated heat exchanger.

4. The system of claim 1, wherein the control valving comprises a distributor with a plurality of valves, each valve configured to regulate flow to one of the heat exchanger flow paths.

5. The system of claim 4, comprising control circuitry configured to simultaneously and independently control each of the plurality of valves based on a sensed parameter of the fluid.

6. The system of claim 1, comprising a sensor for sensing a parameter of the fluid, and wherein the control valving regulates flow of the fluid through each of the flow paths based on the sensed parameter.

7. The system of claim 6, wherein the sensed parameter comprises a temperature or a pressure.

8. The system of claim 6, wherein the sensor is common to all of the heat exchanger flow paths.

9. The system of claim 6, comprising a controller configured to simultaneously and independently open and close valves of the control valving based on the sensed parameter.

10. The system of claim 1, comprising a plurality of sensors each operably coupled to a flow path of the plurality of heat exchanger flow paths and each configured to sense a parameter of the operably coupled flow path; and wherein the control valving regulates flow of the fluid through each of the flow paths based on the sensed parameter of the operably coupled flow path.

11. The system of claim 1, wherein one or more flow paths of the plurality of heat exchanger flow paths are configured to circulate fluid through a plurality of heat exchangers.

12. The system of claim 1, comprising: a compressor configured to compress a gaseous refrigerant; a condenser configured to receive and to condense the compressed refrigerant; an expansion device configured to reduce pressure of the condensed refrigerant; and an evaporator configured to evaporate the refrigerant prior to returning the refrigerant to the compressor; wherein the plurality of heat exchanger flow paths are configured to circulate the refrigerant through the condenser or the evaporator.

13. A method for promoting heat exchange to or from a fluid, the method comprising: controlling valves to simultaneously and independently regulate flow of refrigerant to a plurality of heat exchanger flow paths each coupled downstream of a respective valve; flowing the refrigerant through the plurality of heat exchanger flow paths; and flowing an external fluid through the heat exchanger across the heat exchanger flow paths.

14. The method of claim 13, wherein controlling valves comprises reducing fluid flow to some flow paths of the heat exchanger flow paths and increasing fluid flow to other flow paths of the heat exchanger flow paths.

15. The method of claim 13, wherein controlling valves comprises regulating flow to the plurality of heat exchanger flow paths to reduce superheating of refrigerant within the heat exchanger flow paths.

16. The method of claim 13, wherein controlling valves comprises regulating flow to the plurality of heat exchanger flow paths to minimize the amount of liquid phase refrigerant exiting the heat exchanger flow paths.

17. The method of claim 13, wherein controlling valves comprises opening or closing valves based on a sensed temperature or pressure of each of the plurality of heat exchanger flow paths.

18. A method comprising: sensing a parameter of refrigerant flowing through a heat exchanger; and individually and simultaneously controlling a plurality of valves based on the sensed parameter to regulate flow through the heat exchanger; wherein each valve is fluidly coupled to a tube or group of tubes within the heat exchanger.

19. A distributor comprising: a plurality of flow passages configured to fluidly connect to flow paths of a heat exchanger; and valves disposed in each of the plurality of flow passages and configured to simultaneously regulate flow through each of the plurality of flow passages.

20. The distributor of claim 19, wherein the valves are configured to regulate flow in response to received control signals based on sensed parameters of the flow paths.

21. The distributor of claim 19, comprising an inlet configured to fluidly connect to a refrigerant line of a heating, ventilating, air conditioning, or refrigeration system.

22. The distributor of claim 19, comprising an inlet configured to receive a fluid and to direct the fluid to an interior volume; and wherein the flow passages are axial passages circumferentially disposed around the interior volume and configured to receive the fluid from the interior volume and to direct the fluid through the valves.

23. The distributor of claim 19, comprising a check plate configured to move axially within the interior volume of the distributor and configured to direct flow through the valves when the fluid is received in a first direction and to direct flow around the valves when the fluid is received in an opposite direction.