CN101600929B - Multichannel heat exchanger with dissimilar tube spacing - Google Patents

Abstract

The present invention provides heating, ventilation, air conditioning and refrigeration (HVAC&R) systems (10, 44) and heat exchangers (16, 22, 50, 52) that include different duct spacing configurations. The heat exchangers (16, 22, 50, 52) include sets of multi-pass tubing (92) in fluid communication with each other. A set of multipass tubing (92) has a plurality of tubing (94) spaced at one interval (A) and another set of multipass tubing has a plurality of tubing (96) spaced at a different interval (B) . The different spacing between the multi-pass tubes (92) allows each set of tubes (94, 96) to be configured to suit the properties of the refrigerant flowing in the tubes (94, 96).

Description

Multi-pass heat exchanger with different tube spacing

Cross References to Related Applications

This application claims U.S. Provisional Application No. 60/867,043, filed November 22, 2006, entitled "MICROCHANNEL HEATEXCHANGER APPLICATIONS," and U.S. Provisional Application No. 60/867,043, filed December 27, 2006, entitled "MICROCHANNEL HEAT EXCHANGER APPLICATIONS" .60/882,033 and priority to US Provisional Application No. 60/909,598, filed April 2, 2007, entitled "MICROCHANNEL COIL HEADER," which applications are hereby incorporated by reference.

technical field

This application generally relates to multi-pass heat exchangers. More specifically, the present application relates to coil spacing configurations for multi-pass heat exchangers.

Background technique

Heat exchangers are widely used in heating, ventilation, air conditioning and refrigeration (HVAC&R) systems. Multi-pass heat exchangers typically include multiple-pass tubing for the flow of refrigerant through the heat exchanger. Each multi-channel conduit may have multiple independent flow paths. Fins are located between the tubes to facilitate heat transfer between refrigerant contained in the tube flow paths and outside air passing around the tubes. Multi-pass heat exchangers can be used in small tonnage systems, such as residential systems, or large tonnage systems, such as industrial cooling systems.

Typically, heat exchangers transfer heat by circulating a refrigerant through an evaporation and condensation cycle. In many systems, the refrigerant undergoes a phase change as it flows through a heat exchanger where evaporation and condensation occur. For example, refrigerant may enter an evaporative heat exchanger as a liquid and exit as a vapor. Similarly, refrigerant can enter a condensing heat exchanger as a vapor and exit as a liquid. These phase changes result in liquid and vapor refrigerant flowing through the heat exchanger flow paths. Specifically, one portion of the heat exchanger may contain vapor refrigerant undergoing de-superheat while another portion of the heat exchanger contains liquid undergoing subcooling.

The phase of the refrigerant affects the efficiency of the heat exchanger because different phases of the refrigerant have different heat transfer properties. For example, refrigerant in the vapor phase will flow through the flow passages at a higher velocity than refrigerant in the liquid phase, causing less heat transfer to occur in the tubes containing the refrigerant in the vapor phase. In another example, with a heat exchanger acting as a condenser, a vapor refrigerant would need to give up both latent and sensible heat to become a liquid refrigerant, whereas a liquid refrigerator only gives off sensible heat to undergo subcooling.

Accordingly, there is a need for heat exchanger designs that allow for improved heat transfer performance for both vapor and liquid refrigerant phases. In some systems, it is desirable to vary the heat transfer performance independently for the desuperheating and subcooling processes. This results in more heat exchange for each phase of the refrigerant.

Contents of the invention

The present invention provides heat exchangers and HVAC&R systems having piping configurations designed to meet this need. The described piping configuration finds application in many heat exchangers, but in particular is well suited for use in condensers used in residential air conditioning and heat pump systems. Typically, a heat exchanger has two sets of multi-pass tubes and circulates fluid from one set of tubes to the other. One set of multi-pass conduits has conduits spaced at one interval, and the other set of multi-pass conduits has conduits spaced at a different interval.

In the implementation described below, the first set of multi-pass tubes in the heat exchanger is configured to subject the vapor refrigerant to desuperheating. As the vapor refrigerant flows through the first set of tubes, the vapor condenses into a liquid. The first set of tubes is spaced a distance customized for the desuperheating process. Once the refrigerant condenses into a liquid, the refrigerant flows through a second set of multi-pass tubing configured to subcool the liquid refrigerant. The second set of tubes is spaced a distance customized for the subcooling process. Thus, the tube configuration allows improving the efficiency of the heat exchanger by tailoring each set of tubes to the refrigerant phase flowing through the tubes.

Description of drawings

These and other features, aspects and advantages of the present invention will be better understood when read in the following detailed description when taken in conjunction with the accompanying drawings in which like numerals represent like parts throughout:

Figure 1 shows an exemplary residential air conditioning or heat pump system of the type that may employ a heat exchanger manufactured or constructed in accordance with the techniques of the present invention;

Figure 2 is a partially exploded view of the external unit of the system of Figure 1 with the upper assembly lifted to expose certain system components, including the heat exchanger;

Figure 3 shows an exemplary commercial or industrial HVAC&R system employing chillers and air handlers to cool buildings and may also employ heat exchangers according to the techniques of the present invention;

4 is a schematic view of an exemplary air conditioning system that may employ one or more heat exchangers with coil spacing configurations in accordance with aspects of the present invention;

5 is a schematic view of an exemplary heat pump system that may employ one or more heat exchangers with coil spacing configurations in accordance with aspects of the present invention;

6 is a perspective view of an exemplary heat exchanger having a coil spacing configuration according to an aspect of the present invention; and

Figure 7 is a detailed perspective view of the heat exchanger of Figure 6 with a portion of the manifold cut away.

Detailed ways

Turning now to the drawings, and referring first to FIGS. 1-3 , which illustrate exemplary applications of aspects of the present invention. In general, the invention can be used in a wide range of installations, both in the HVAC&R field and beyond. However, in currently conceivable applications, the present invention may be used in residential, commercial, light industrial, heavy industrial and any other application for heating or cooling a volume or enclosure such as a dwelling, building, structure, or the like. Furthermore, the invention can be used in industrial applications, where appropriate, for the basic refrigeration and heating of various fluids. The specific application shown in Figure 1 is for residential heating and cooling. Typically, dwellings designated by the letter R are equipped with an outdoor unit that is operatively coupled to an indoor unit. The outdoor unit is usually located near the side of the dwelling and is covered by an enclosure to protect system components and keep leaves and other contaminants from entering the unit. Indoor units can be located in utility rooms, attics, basements, etc. The outdoor unit is coupled to the indoor unit by a refrigerant pipe RC that conveys a predominantly liquid refrigerant in one direction and a predominantly vaporized refrigerant in the opposite direction.

In operation, when the system shown in Figure 1 is operating as an air conditioner, the coil in the outdoor unit acts as a condenser for regenerating vaporized refrigerant flowing from the indoor unit IU to the outdoor unit OU via one of the refrigerant pipes. condensation. In these applications, the coils of the indoor units marked with reference IC are used as evaporation coils. The evaporating coil receives liquid refrigerant (which can be expanded by an expansion device described below) and evaporates the refrigerant before returning to the outdoor unit.

In operation, the outdoor unit draws in ambient air through the side indicated by the arrow pointing to the side of the unit OU, is forced by a fan (not shown) through the outer unit coil and expels the air as indicated by the arrow above the outdoor unit. When operating as an air conditioner, the air is heated by the condensing coils in the outdoor unit and this air leaves the top of the unit at a higher temperature than it entered the side. Instead, the air is blown through the indoor coil IC and then circulated through the dwelling through the duct structure D, as indicated by the arrows in FIG. 1 . The entire system operates to maintain the desired temperature set by the thermostat T. When the temperature sensed within the dwelling is higher than the set point on the thermostat (plus a small amount), the air conditioner will operate to cool additional air for circulation through the dwelling. When the temperature reaches the set point (minus a small amount), the unit will temporarily stop the refrigeration cycle.

When the unit of Figure 1 is operating as a heat pump, the roles of the coils are simply reversed. That is, the coils of the outdoor unit will act as an evaporator to evaporate the refrigerant and thereby cool the air entering the outdoor unit as it passes around the outdoor unit coils. Instead, the indoor coil IC will receive the flow of air blowing around it and heat the air by condensing the refrigerant.

Figure 2 shows a partially exploded view of one of the units shown in Figure 1, in this case the outdoor unit OU. In general, the unit may be considered to comprise an upper assembly UA constructed of a housing, fan assembly, fan drive motor, and the like. In the display in Figure 2, the fan and fan drive motor are not visible because they are hidden by the surrounding housing. The outdoor coil OC is housed in the enclosure and is generally positioned to surround, or at least partially surround, other system components, such as compressors, expansion devices, control circuits, etc., as will be described more fully hereinafter.

Figure 3 shows another exemplary application for the invention, in this case an HVAC&R system for establishing environmental management. In the embodiment shown in Figure 3, the building BL is cooled by a system comprising a chiller CH, typically located on or near the building or in a control room or basement. In the embodiment shown in Fig. 3, the cooler CH is an air cooling device which uses a refrigeration cycle to cool water. Water circulates through water pipes WC to the building. The water pipes lead to air handlers (AH) at each floor or section of the building. The air handler is also coupled to a ductwork DU adapted to blow in air from the external inlet OL.

In operation, the chiller cools water circulated to the air handler and includes a heat exchanger as described above for evaporating and condensing the refrigerant. The air blown around the additional coils receiving the water in the air handler increases the temperature of the water and decreases the temperature of the circulating air. The cooled air is then sent to various locations in the building via additional ductwork. Ultimately, the distribution of air is sent to diffusers that deliver the cooled air to offices, apartments, hallways and any other interior spaces within the building. In many applications, a thermostat or pilot (not shown in Figure 3) will be used to control air flow through and from each air handler and duct structure to maintain The desired temperature at each location.

Figure 4 shows an air conditioning system 10 which uses multi-pass ducting. Refrigerant flows through the system in a closed refrigeration loop 12 . A refrigerant can be any fluid that absorbs and releases heat. For example, the refrigerant may be hydrofluorocarbon (hydrofluorocarbon: HFC)-based R-410A, R-407, or R-134a, or it may be carbon dioxide (R-744a) or ammonia (R-717). The air conditioning system 10 includes a control device 14 which enables the system 10 to cool the environment to a prescribed temperature.

System 10 cools the environment by circulating a refrigerant in closed refrigeration loop 12 through condenser 16 , compressor 18 , expansion device 20 , and evaporator 22 . The refrigerant enters the condenser 16 as a high-pressure and high-temperature vapor and flows through the multi-channel pipes of the condenser 16 . A fan 24 driven by a motor 26 draws air across the multi-pass duct. Fan 24 may draw or push air through the ducts. Heat is transferred from the refrigerant vapor to the air, forming heated air 28 and causing the refrigerant vapor to condense into a liquid. The liquid refrigerant then flows into expansion device 20 where it expands to form a low pressure cryogenic liquid. Typically, the expansion device 20 is a thermal expansion valve (TXV); however, in other embodiments, the expansion device may be an orifice or a capillary tube. As will be appreciated by those skilled in the art, after the refrigerant leaves the expansion device, there will be some vapor refrigerant in addition to the liquid refrigerant.

From the expansion device 20, the refrigerant enters the evaporator 22 and flows through the evaporator multi-pass tubing. A fan 30 driven by a motor 32 draws air across the multi-pass duct. Heat is transferred from the air to the refrigerant liquid, forming cooled air 34 and causing the refrigerant liquid to boil into a vapor. As will be appreciated by those skilled in the art, the fan may be replaced with a pump that draws fluid across the multi-pass tubing.

The refrigerant then flows to compressor 18 as a low temperature, low pressure vapor. Compressor 18 reduces the volume available for refrigerant vapor, thereby 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 turbo compressor machine. Compressor 18 is driven by an electric motor 36 that receives power from a variable speed drive (VSD) or a direct AC or DC power source. In one embodiment, the motor 36 receives a fixed line voltage and frequency from an AC power source, although in some 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 leaves compressor 18 as a high temperature, high pressure vapor ready to enter the condenser and begin the refrigeration cycle again.

The operation of the refrigeration cycle is managed by a control device 14 comprising a control circuit 38 , an input device 40 and a temperature sensor 42 . Control circuitry 38 is coupled to motors 26, 32, 36 which drive condenser fan 24, evaporator fan 30 and compressor 18, respectively. The control circuitry uses information received from the input devices 40 and sensors 42 to determine when to operate the motors 26, 32, 36 that drive the air conditioning system. For example, in a residential air conditioning system, input device 40 may be a programmable 24 volt thermostat that provides a temperature setpoint to control circuit 38 . Sensor 42 determines the ambient air temperature and provides this temperature to control circuit 38 . The control circuit 38 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, the control circuit turns on the motors 26 , 32 , 36 to operate the air conditioning system 10 . In addition, the control circuit can implement hardware or software control algorithms to control the air conditioning system. In some embodiments, control circuitry 38 may include an analog-to-digital (A/D) converter, a microprocessor, 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 capable of sensing temperature and pressure of refrigerant, heat exchangers, inlet and outlet air, etc.

Figure 5 shows a heat pump system 44 using multi-pass piping. The refrigerant flows through the reversible cooling/heating loop 46 because the heat pump system can be used for both heating and cooling. A refrigerant can be any fluid that absorbs and releases heat. Furthermore, the heating and cooling operations are controlled by the control device 48 .

The heat pump system 44 includes an outer coil 50 and an inner coil 52, both of which function as heat exchangers. As mentioned above, the coils can be used as evaporators or condensers, depending on the mode of operation of the heat pump. For example, when the heat pump system 44 is operating in a cooling ("AC") mode, the outer coil 50 acts as a condenser, releasing heat to the outside air; and the inner coil 52 acts as an evaporator, absorbing heat from the inside air. Conversely, when the heat pump system 44 is operating in a heating mode, the outer coil 50 acts as an evaporator, absorbing heat from the outside air, and the inner coil 52 acts as a condenser, releasing heat to the inside air. A reversing valve 54 is located on the reversing loop 46 between the coils to control the direction of refrigerant flow and thereby switch the heat pump between heating and cooling modes.

The heat pump system 44 also includes two metering devices 56, 58 for reducing the pressure and temperature of the refrigerant before it enters the evaporator. Those skilled in the art will appreciate that the dosing device is also used to regulate the flow of refrigerant into the evaporator so that the amount of refrigerant entering the evaporator is equal to the amount of refrigerant leaving the evaporator. The use of the metering device depends on the operating mode of the heat pump. For example, when the heat pump system is operating in cooling mode, the refrigerant bypasses dosing device 56 and flows through dosing device 58 before entering inner coil 52 which acts as an evaporator. Similarly, when the heat pump system is operating in heating mode, the refrigerant bypasses dosing device 58 and flows through dosing device 56 before entering outer coil 50 which acts as an evaporator. In other embodiments, one dosing device may be used for both heating and cooling modes. The dosing devices 56, 58 are typically thermal expansion valves (TXV), but may also be orifices or capillaries.

The refrigerant enters the evaporator as a low temperature, low pressure liquid which is the outer coil 50 in the heating mode and the inner coil 52 in the cooling mode. Those skilled in the art will appreciate that some vapor refrigerant may also be present as a result of the expansion process occurring in the dosing devices 56 , 58 . The refrigerant flows through the multi-pass tubes in the evaporator and absorbs heat from the air, turning the refrigerant into a vapor. In cooling mode, the room air passing around the multi-pass ducts is also dehumidified. Moisture from the air condenses on the outer surface of the multi-pass tubing and is thus removed from the air.

After leaving the evaporator, the refrigerant flows through reversing valve 54 and into compressor 60 . Compressor 60 reduces the volume of the refrigerant vapor, thereby increasing the temperature and pressure of the vapor. Again, the compressor may be any suitable compressor, such as a screw compressor, reciprocating compressor, rotary compressor, pendulum compressor, scroll compressor or turbo compressor.

From the compressor, the vapor refrigerant at increased temperature and pressure flows into the condenser, whose position is determined by the heat pump mode. In cooling mode, refrigerant flows into the outer coil 50 (which acts as a condenser). A fan 62 powered by a motor 64 draws air around the multi-pass tubes containing the refrigerant vapor. Those skilled in the art will appreciate that the fan could be replaced by a pump that draws fluid across the multi-pass tubing. 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 the inner coil 52 which acts as a condenser. A fan 66 powered by a motor 68 draws air around the multi-pass tubes containing the refrigerant vapor. Heat from the refrigerant is transferred to the interior air causing the refrigerant to condense into a liquid.

After leaving the condenser, the refrigerant flows through a dosing device (56 in heating mode and 58 in cooling mode) and returns to the evaporator (outer coil 50 in heating mode and inner coil in cooling mode Coil 52), where the process begins again.

The motor 70 drives the compressor 60 and circulates refrigerant through the reversible cooling/heating loop 46 in the heating mode and in the cooling mode. The motor can receive power directly from an AC or DC power source or from a variable speed drive (VSD). As in the previous example, 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 operation of the motor 70 is controlled by a control circuit 72 . The control circuit 72 receives information from the input device 74 and the sensors 76, 78, 80 and uses the information to control the operation of the heat pump system 44 in the cooling mode and the heating mode. For example, in a cooling mode, the input device provides a temperature setpoint to the control circuit 72 . Sensor 80 measures and provides the ambient room air temperature to control circuit 72 . The control circuit 72 then compares the air temperature to the temperature set point and if the air temperature is above the temperature set point, the control circuit engages the compressor motor 70 and the fan motors 64 and 68 to operate the cooling system. Likewise, in the heating mode, the control circuit 72 compares the air temperature from the sensor 80 to the temperature set point from the input device 74, and if the air temperature is below the temperature set point, the control circuit engages the motors 64, 68, 70 , to run the heating system.

The control circuit 72 also uses information received from the input device 74 to switch the heat pump system 44 between a heating mode and a cooling mode. For example, if the input device is set to a cooling mode, the control circuit 72 sends a signal to the solenoid 82 to place the selector valve 54 in the air conditioning position 84 . Thus, the refrigerant will flow through the reversible loop 46 as follows: the refrigerant leaves the compressor 60 , condenses in the outer coil 50 , is expanded by the dosing device 58 , and is evaporated by the inner coil 52 . Likewise, if the input device is set to the heating mode, the control circuit 72 sends a signal to the solenoid 82 to place the reversing valve 54 in the heat pump position 86 . Thus, the refrigerant will flow through the reversible loop 46 as follows: the refrigerant leaves the compressor 60 , condenses in the inner coil 52 , is expanded by the dosing device 56 , and is evaporated by the outer coil 50 .

Control circuitry 72 may implement hardware or software control algorithms to control heat pump system 44 . In some embodiments, the control circuit may include, an analog-to-digital (A/D) converter, a microprocessor, non-volatile memory, and an interface board.

The control circuit may also initiate a defrost cycle when the system 44 is operating in the heating mode. When the outside temperature approaches freezing, moisture directed into the outside air around the outer coil 50 can condense on the coil and freeze. Sensor 76 measures the outside air temperature and sensor 78 measures the temperature of the outer coil 50 . These sensors provide temperature information to a control circuit that determines when to initiate a defrost cycle. For example, the system 44 may be in a defrost mode if either of the sensors 76, 78 provides a temperature below freezing to the control circuit. In the defrost mode, the solenoid 82 is actuated to place the selector valve 54 in the air conditioning position 84 and the motor 64 is turned off to shut off air flow through the excess passage. The system 44 then operates in cooling mode until the increased temperature and pressure of refrigerant flowing through the outer coil defrosts the coil 50 . Once the sensor 78 detects that the coil 50 has been defrosted, the control circuit 72 returns the reversing valve 54 to the heat pump position 86 . Those skilled in the art will understand that defrost cycles can be set to occur at many different time and temperature combinations.

FIG. 6 is a perspective view of an exemplary heat exchanger that may be used in air conditioning system 10 or heat pump system 44 . The exemplary heat exchanger may be the condenser 16, the evaporator 22, the outer coil 50 or the inner coil 52, as shown in FIGS. 4 and 5 . It should be noted that in similar or other systems, the heat exchanger could be used as part of a chiller or in any other exchange application. The heat exchanger includes headers 88 , 90 connected by multi-pass tubing 92 . Although 30 pipes are shown in Figure 3, the number of pipes may vary. The headers and piping can be fabricated from aluminum or any other material that provides good heat transfer. Refrigerant flows from header 88 through first conduit 94 to header 90 . The refrigerant then returns to header 88 through second conduit 96 . The first conduit 94 may have the same construction as the second conduit, or the first conduit may differ from the second conduit in properties, such as construction material or shape. In some embodiments, the heat exchanger may be rotated approximately 90 degrees so that the multi-pass tubing extends vertically between the top header and the bottom header. Furthermore, the heat exchanger may be inclined at an angle relative to the vertical. Furthermore, although the multi-pass conduit is described as having an oblong shape, the conduit may have any shape, such as the conduit having a cross section in the form of a rectangle, square, circle, oval, ellipse, triangle, trapezoid, or parallelogram. section. In some embodiments, the tubing may have a diameter ranging from 0.5mm to 3mm. It should be noted that the heat exchanger may be arranged in one plane or in a slab, or may have bends, corners, contours, etc.

Refrigerant enters the heat exchanger through inlet 98 and exits the heat exchanger through outlet 110 . Although FIG. 6 shows an inlet at the top of the manifold 88 and an outlet at the bottom of the manifold, the locations of the inlet and outlet may be reversed so that fluid enters at the bottom and exits at the top. Fluid may also enter and exit the manifold from multiple inlets and outlets located on the bottom surface, side surfaces, or top surface of the manifold. A baffle 102 separates portions of the inlet 98 and outlet 100 of the manifold 88 . Although two partitions 102 are shown, any number of one or more partitions may be used to form the inlet 98 and outlet 100 separations.

Fins 104 are located between the multi-pass tubes 92 to facilitate heat transfer between the tubes 92 and the environment. In one embodiment, the fins are fabricated from aluminum, brazed or otherwise joined to the tubes, and positioned generally perpendicular to the flow of refrigerant. However, in other embodiments, the fins may be fabricated from other materials that facilitate heat transfer, or may extend parallel to or at varying angles relative to the flow of refrigerant. Furthermore, the fins may be louvered fins, corrugated fins, or any suitable type of fins.

In a typical heat exchanger application, refrigerant may enter header 88 in one phase and leave header 88 in another phase. For example, if the heat exchanger is operating as a condenser, the refrigerant may enter inlet 98 as a vapor (or a mixture of vapor and liquid). As the vapor passes through the first multi-pass conduit 94, the vapor releases heat to the external environment, causing the vapor to undergo desuperheating and condense into a liquid. Subsequently, as the liquid refrigerant passes through the second multi-pass conduit 96, the liquid releases heat to the external environment, causing subcooling. Air flowing over the fins 104 and around the tubes facilitates heat transfer for both the liquid and vapor phases of the refrigerant. In some embodiments, the refrigerant flowing through first conduit 92 may have a temperature of up to about 78°C (172°F), and the refrigerant flowing through second conduit 96 may have a temperature of about 41°C (106°F). temperatures, but these temperatures can vary with the refrigerant used and the pressure acting in the piping.

To improve the heat transfer performance of the heat exchanger, the tubes 92 are spaced at different distances. The first conduit 92 containing the refrigerant mainly in the vapor phase has a larger first interval A, and the second conduit 96 containing the refrigerant primarily in the liquid phase has a second smaller interval B. The first spacing A allows for a greater airflow 110 between the first ducts 94 than the airflow 112 between the second ducts 96 . This difference in air flow between duct sections improves heat transfer performance. For example, in one embodiment in which the heat exchanger acts as a condenser, the vapor refrigerant flowing through the first conduit may have a temperature much higher than the temperature of the air. The increased air flow can result in more heat being transferred from the refrigerant to the air, maximizing the temperature differential. The liquid refrigerant flowing through the second pipe may have a temperature slightly higher than the air temperature. Therefore, a smaller amount of air flow is required to transfer heat from the refrigerant to the air.

Those skilled in the art will appreciate that different spacings also result in different fin heights, which contribute to improved heat transfer between tube sections. For example, the first interval A allows taller fins than the second interval B. The fins between the first tubes 94 may have a larger surface area allowing for more heat transfer between the first tubes and the outside air. The fins between the second tubes 96 may have a smaller surface area so that there is less heat transfer between the second tubes and the outside air.

In some embodiments, the first interval A may be greater than the second interval B, as shown in FIG. 6 . However, in other embodiments, the first interval may be smaller than the second interval. Furthermore, the difference between the first compartment and the second compartment may vary based on the properties of the heat exchanger such as refrigerant used, outside air temperature, capacity and materials used for construction. For example, in an embodiment employing a condenser with aluminum tubing, the first spacing may be twice the second spacing. Furthermore, the ratio between the number of first and second tubes can vary based on the performance of each heat exchanger. By way of further example, there may be an even number of first and second conduits, or three times as many second conduits as first conduits. In an embodiment employing a condenser with aluminum tubes, the second tube may be four times the size of the first tube. Also, in the presently contemplated embodiment, the spacing between the ducts may range from 0.2" to 0.6", with larger spacings having greater values than smaller spacings, but it will be understood that the spacing may be adapted for thermal Specific thermal performance and transfer for exchanger design.

Figure 7 shows a perspective view of the heat exchanger shown in Figure 6 with a portion of the manifold 88 cut away to show the interior of the manifold. As shown, the refrigerant exits header 88 through flow passage 113 included in first conduit 94 and returns to header 88 through flow passage 113 included in second conduit 96 . In some embodiments, the flow passages may be arranged parallel to each other. Additionally, any number of flow paths may be included in the tubing. For example, in one embodiment, the conduits may contain 18 flow paths each.

A partition 102 separates the first duct section from the second duct section of the manifold. As mentioned above, the refrigerant in the first pipe section of the header may be in a different phase than the refrigerant in the second pipe section. The partitions 102 are spaced apart to form an isolated volume 114 in the manifold. Additionally, an isolated duct 116 may be located between the bulkheads 102 to provide separation between the first duct 94 and the second duct 96 . The isolated volume 114 and isolated tubing can provide insulation between tubing sections and allow the heat transfer performance of each tubing section to be improved independently of each other. For example, in an embodiment where the heat exchanger is used as a condenser, a first tube may contain high temperature vapor while a second tube contains low temperature liquid. The isolated space and isolated tubing provide insulation between the vapor and liquid portions, thus preventing heat transfer from the vapor refrigerant to the liquid refrigerant. As a result, the liquid refrigerant can reach lower temperatures because it absorbs less heat from the vapor refrigerant.

It should be noted that this specification uses the terms "multi-pass" piping or "multi-pass heat exchanger" to refer to devices in which heat transfer piping includes multiple flow paths between manifolds that distribute flow to or collect flow from the piping . Many other terms are used in the art for similar devices. These alternative terms may include "microchannel" and "microport". The term "microchannel" is sometimes taken to mean a conduit having fluid channels on the order of micrometers or smaller. However, in this specification, these terms are not intended to set any specific higher or lower size limits. Rather, the term "multi-pass" used herein to describe and enable embodiments to be claimed is intended to cover all such dimensions. Other terms sometimes used in the art include "parallel flow" and "brazed aluminum". However, all such devices and structures shall be included within the scope of the term "multi-path". Typically, a "multi-pass" conduit will include flow paths disposed either in the plane or across the width of a generally flat planar conduit, but the invention is not intended to be limited to any particular geometry unless otherwise stated in the appended claims.

While only certain features of the invention have been shown 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 to cover all such modifications and changes as fall within the true spirit of the invention.

Claims (9)

1. A heat exchanger comprising: first master (88); second master (90); a first plurality of multi-pass conduits (94) in fluid communication with the first manifold (88) and the second manifold (90), the first plurality of multi-pass conduits (94) being spaced apart from each other by a first interval (A), wherein the first spacing has a first distance between adjacent tubes of the first plurality of multi-pass tubes; and A second plurality of multi-pass conduits (96) in fluid communication with the first manifold (88) and the second manifold (90), the second plurality of multi-pass conduits (96) at a second interval different from the first interval ( B) spaced apart from each other, wherein the second spacing has a second distance between adjacent tubes of the second plurality of multi-pass tubes, Radiating fins (104) are disposed between the first and second plurality of multi-passage pipes, wherein the fins disposed between the first plurality of multi-passage pipes (94) have the same height as those disposed in the second plurality of multi-passage pipes The fins have different heights between the multi-pass conduits (96). 2. The heat exchanger according to claim 1, wherein the first interval (A) is larger than the second interval (B). 3. The heat exchanger according to claim 1, comprising a baffle (102) in the first header (88) to force the incoming flow introduced into the first header (88) to pass through the first plurality of The multi-pass piping (94) reaches the second manifold (90) and separates the incoming flow from the exhaust flow exiting the second plurality of multi-pass piping (96) into the first manifold (88). 4. The heat exchanger according to claim 3, further comprising another baffle (102) located in the first manifold (88), whereby the two baffles make a plurality of first plurality of multi-pass tubes (94 ) and at least one multi-pass pipe (116) between the second plurality of multi-pass pipes (96) is isolated, wherein the two partitions (102) are configured to allow recirculation flow from the first manifold (88) The inlet side of the first plurality of multi-pass pipes (94) leads to the second manifold (90), and from the second manifold leads to the outlet side of the first manifold (88) through the second plurality of multi-pass pipes (96) . 5. The heat exchanger of claim 1, wherein the tubes (94) of the first plurality of multi-pass tubes (94) are configured differently from the tubes (96) of the second plurality of multi-pass tubes (96). )same. 6. The heat exchanger of claim 1, wherein each tube (64, 96) of the first and second plurality of multi-pass tubes includes a plurality of substantially parallel flow paths (113) disposed along its width ). 7. A heat exchanger comprising: first master (88); second master (90); a first plurality of multi-pass conduits (94) in fluid communication with the first manifold (88) and the second manifold (90), the first plurality of multi-pass conduits (94) being spaced apart from each other by a first interval (A), wherein the first spacing has a first distance between adjacent tubes of the first plurality of multi-pass tubes; A second plurality of multi-pass conduits (96) in fluid communication with the first manifold (88) and the second manifold (90), the second plurality of multi-pass conduits (96) at a second interval different from the first interval (A) two bays (B) are spaced apart from each other, wherein the second bay has a second distance between adjacent pipes of the second plurality of multi-pass pipes; and a bulkhead (102) in the first manifold (88) between the first plurality of multi-pass conduits (94) and the second plurality of multi-pass conduits (96) to allow recirculation flow from the first plurality of multi-pass conduits (96) The inlet (98) side of a manifold (88) leads to a second manifold (90) through a first plurality of multi-pass conduits (94), and from the second manifold (90) through a second plurality of multi-pass conduits (96) leading to the outlet (100) side of the first manifold (88); and Radiating fins (104) are disposed between the first and second plurality of multi-passage pipes, wherein the fins disposed between the first plurality of multi-passage pipes (94) have the same height as those disposed in the second plurality of multi-passage pipes The fins have different heights between the multi-pass conduits (96). 8. The heat exchanger according to claim 7, wherein the first interval (A) is larger than the second interval (B). 9. The heat exchanger according to claim 7, further comprising another baffle (102) positioned in the first manifold (88), so that the two baffles make a plurality of first multipass pipes (94) and At least one multi-pass conduit (116) is isolated between the plurality of second multi-pass conduits (96), wherein the two partitions (102) are configured to allow circulation flow from the inlet of the first manifold (88) The side leads to the second manifold (90) through the first plurality of multi-pass conduits (94), and from the second manifold to the outlet side of the first manifold (88) through the second plurality of multi-pass conduits (96).

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