HK1156098A - Microchannel heat exchanger including multiple fluid circuits - Google Patents

Description

Microchannel heat exchanger comprising a multi-fluid circuit

RELATED APPLICATIONS

This application claims priority from U.S. provisional patent application No.61/050,387 filed 5/2008.

Technical Field

The present invention relates generally to microchannel heat exchangers including multi-fluid circuits.

Background

A microchannel heat exchanger (MCHX) exchanges heat between refrigerant and a fluid, such as air. The microchannel heat exchanger includes a plurality of microchannel tubes. Refrigerant flows through the plurality of microchannel tubes and air flows over the plurality of microchannel tubes.

Microchannel heat exchangers utilize a single refrigerant circuit. Refrigerant enters the circuit through an inlet and multiple passes through the microchannel heat exchanger are available. The refrigerant then exits the circuit through an outlet. This results in a high refrigerant side pressure drop for a given amount of refrigerant side heat transfer. This adverse relationship can affect overall system performance, particularly under high outdoor ambient conditions, which can result in discharge pressures higher than comparable Round Tube Plate Fin (RTPF) heat exchangers.

Disclosure of Invention

The microchannel heat exchanger includes a plurality of microchannel tubes including a first plurality of microchannel tubes and a second plurality of microchannel tubes. The first loop of the microchannel heat exchanger includes a first plurality of microchannel tubes, and a portion of the first fluid flows through the first plurality of microchannel tubes and exchanges heat with the second fluid. The second loop of the microchannel heat exchanger includes a second set of microchannel tubes, and the remainder of the first fluid flows through the second set of microchannel tubes and exchanges heat with the second fluid.

The first fluid from the first circuit and the first fluid from the second circuit are combined into a common stream.

In another example, a refrigeration system includes: a compressor for compressing a refrigerant; a condenser for cooling the refrigerant; an expansion device that expands the refrigerant; and an evaporator for heating the refrigerant. One of the condenser and the evaporator is a microchannel heat exchanger. The microchannel heat exchanger includes a plurality of microchannel tubes including a first plurality of microchannel tubes and a second plurality of microchannel tubes. The first circuit of the microchannel heat exchanger includes a first plurality of microchannel tubes, and a portion of the refrigerant flows through the first plurality of microchannel tubes and exchanges heat with air. The second circuit of the microchannel heat exchanger includes a second set of microchannel tubes, and the remainder of the refrigerant flows through the second set of microchannel tubes and exchanges heat with air. The refrigerant from the first circuit and the refrigerant from the second circuit are combined into a common flow.

These and other features of the present invention will be better understood from the following specification and drawings.

Drawings

The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:

FIG. 1 illustrates a prior art refrigeration system;

FIG. 2 illustrates a multi-loop microchannel heat exchanger;

FIG. 3 illustrates a multi-loop microchannel heat exchanger including a subcooler;

Detailed Description

Fig. 1 shows a refrigeration system 20 that includes a compressor 22, a first heat exchanger 24, an expansion device 26, and a second heat exchanger 28. Refrigerant circulates though the closed loop refrigeration system 20.

When the refrigeration system 20 is operating in the cooling mode, refrigerant exits the compressor 22 at a high pressure and enthalpy and flows through the first heat exchanger 24, the first heat exchanger 24 acting as a condenser. In the first heat exchanger 24, the refrigerant rejects heat to air and is condensed into a liquid, which exits the first heat exchanger 24 at a low enthalpy and a high pressure. A fan 30 directs air through the first heat exchanger 24. The cooled refrigerant then passes through an expansion device 26, which expands the refrigerant to a low pressure. After expansion, the refrigerant flows through the second heat exchanger 28, and the second heat exchanger 28 functions as an evaporator. In the second heat exchanger 28, the refrigerant accepts heat from the air and exits the second heat exchanger 28 at a high enthalpy and a low pressure. A fan 32 directs air through the second heat exchanger 28. The refrigerant then flows to the compressor 22, completing the cycle.

When the refrigeration system 20 is operating in the heating mode, the refrigerant flow is reversed using the four-way valve 34. The first heat exchanger 24 receives heat from the air and acts as an evaporator, and the second heat exchanger 28 dissipates heat to the air and acts as a condenser. For ease of reference, the microchannel heat exchanger may be referred to as microchannel heat exchanger 38 and is shown in more detail in fig. 2.

Either or both of the heat exchangers 24 and 28 may be microchannel heat exchangers 38. The microchannel heat exchanger 38 may be part of a refrigeration system 20 for a microdevice, an automotive air conditioner, or a residential system.

Fig. 2 illustrates a first example microchannel heat exchanger 38. The microchannel heat exchanger 38 includes an entry/exit header 40, a return header 42, and microchannel tubes 44 extending between the headers 40 and 42. The microchannel tubes 44 are substantially parallel. Each microchannel tube 44 is a flat multi-port tube with each port having a hydraulic diameter of less than 1 mm.

The microchannel heat exchanger 38 includes a plurality of separate and distinct refrigerant sections or circuits. In one example, the microchannel heat exchanger 38 includes a first loop 46 and a second loop 48 that are separate from each other. In the example described below, the refrigerant takes two passes through each refrigerant circuit 46 and 48. However, any number of passes through each refrigerant circuit 46 and 48 may be available for the refrigerant. For example, the refrigerant may only have one pass through the microchannel heat exchanger 38 or may have more than two passes through the microchannel heat exchanger 38. Flow is defined as one pass through the microchannels 44 between the headers 40 and 42. Thus, the refrigerant takes two passes through the microchannel tubes 44 to complete the circuit.

In one example, the microchannel heat exchanger 38 is a condenser and the distributor 112 splits the refrigerant from the compressor 22 into two paths. One refrigerant flow passes through the coils of the first circuit 46 and one refrigerant flow passes through the coils of the second circuit 48. In one example, the refrigerant is split equally between the two circuits 46 and 48.

The dividing wall 56 divides the inlet/outlet header 40 into a first inlet/outlet section 52 and a second inlet/outlet section 54, preventing refrigerant flow between the sections 52 and 54. The divider wall 100 divides the first entry/exit section 52 into a first entry section 104 and a first exit section 102. The partition wall 106 divides the second entry/exit section 54 into a second entry section 108 and a second exit section 110. A dividing wall 62 divides the return header 42 into the first return section 58 and the second return section 60, preventing refrigerant flow between the sections 58 and 60.

Refrigerant enters the first circuit 46 through an inlet 64. In one example, refrigerant in the first entry section 104 of the first entry/exit section 52 of the entry/exit header 40 flows through the bank 114 of microchannel tubes 44 in the direction a, rejecting heat to air flowing over the microchannel tubes 44. The refrigerant then flows into the first return section 58 of the return header 42. The refrigerant flow then turns 180 ° in the first return section 58 and flows back into the other set 116 of microchannel tubes 44 in the opposite second direction B, dissipating additional heat to the air flowing over the microchannel tubes 44. This pattern is repeated for additional passes. The refrigerant then enters the first exit section 102 of the first entry/exit section 52 of the entry/exit header 40 and exits the first circuit 46 through the outlet 68. Groups 114 and 116 of microchannel tubes 44 are dedicated to first loop 46.

In another example, refrigerant enters the first circuit 46 through the first exit section 102 and exits the first circuit 46 through the first entry section 104.

Refrigerant enters the second circuit 48 through an inlet 70. The refrigerant in the second entry section 108 of the second entry/exit section 54 of the entry/exit header 40 flows in the direction a through the set 118 of microchannel tubes 44 and rejects heat to the air flowing over the microchannel tubes 44. The refrigerant then flows to the second return section 60 of the return header 42. The refrigerant flow then turns 180 ° in the second return section 60 and flows back to the other set 120 of microchannel tubes 44 in the opposite second direction B, dissipating additional heat to the air flowing over the microchannel tubes 44. This pattern is repeated for additional passes. The refrigerant then enters the second exit section 110 of the second entry/exit section 54 of the entry/exit header 40 and exits the second circuit 48 through the outlet 74. Groups 118 and 120 of microchannel tubes 44 are dedicated to second loop 48.

In another example, refrigerant enters the second circuit 48 through the second exit section 110 and exits the second circuit 48 through the second entry section 108.

The refrigerant from the outlets 68 and 74 is combined into a single flow path and then directed to the expansion device 26.

Although two refrigerant circuits 46 and 48 are shown and described as each including two passes through the microchannel tubes 44, it should be understood that the microchannel heat exchanger 38 may include any number of circuits and that the refrigerant in each circuit may achieve any number of passes through the microchannel heat exchanger 38.

Further, the microchannel heat exchanger 38 may be an evaporator, with refrigerant from the expansion device 26 divided into multiple circuits and receiving heat from air flowing over the microchannel tubes 44 before flowing to the compressor 22.

By employing multiple refrigerant circuits in the microchannel heat exchanger 38, the mass flow of refrigerant is divided equally between the multiple circuits, thereby reducing the refrigerant side pressure drop of the refrigerant and improving refrigerant side heat transfer. The refrigerant side heat transfer can be further enhanced by optimally selecting the number of passes in each circuit and the number of microchannel tubes 44 per pass. This helps to reduce the refrigerant side pressure drop and also reduces charge sensitivity of the microchannel heat exchanger 38.

Fig. 3 illustrates a second example microchannel heat exchanger 76. The microchannel heat exchanger 76 includes the features of the microchannel heat exchanger 38 of fig. 2 and a subcooler 78 (third loop). In the example shown and described, the microchannel heat exchanger 76 is a condenser. The microchannel heat exchanger 76 may be an evaporator.

The subcooler 78 is formed by subcooler entry/exit section 80 of entry/exit header 40, return subcooler section 82 of return header 42, and banks 122 and 124 of microchannel tubes 44. A dividing wall 86 separates the subcooler entry/exit section 80 from the sections 52 and 54 of the entry/exit header 40 to prevent refrigerant flow between the sections 52, 54 and 80, and a dividing wall 88 separates the return subcooler section 82 from the sections 58 and 60 of the return header 42 to prevent refrigerant flow between the sections 58, 60 and 82. The subcooler entry/exit section 80 is further divided by a dividing wall 126, the dividing wall 126 dividing the subcooler entry/exit section 80 into a subcooler entry section 128 and a subcooler exit section 130 to enable flow in and out on the same side of the microchannel heat exchanger 76.

The refrigerant exchanges heat with air as described above with reference to fig. 2. The refrigerant from the outlets 68 and 74 is combined into a single path and the refrigerant enters the inlet 90 of the subcooler circuit 96. Refrigerant in the subcooler entry section 128 of the subcooler entry/exit section 80 of the entry/exit header 40 flows through the bank 122 of microchannel tubes 44 in direction A, dissipating heat to the air flowing over the microchannel tubes 44. The refrigerant then enters the return subcooler section 82 of the return header 42. The refrigerant flow then turns 180 ° in the return subcooler section 82 and flows back to the other bank 124 of microchannel tubes 44 in the opposite second direction B, dissipating additional heat to the air flowing over the microchannel tubes 44. The refrigerant then enters the subcooler exit section 130 of the subcooler entry/exit section 80 of the entry/exit header 40 and exits the subcooler circuit 96 through the outlet 94. The refrigerant is then directed to an expansion device 26. The subcooler banks 122 and 124 of microchannel tubes 44 are dedicated to subcooler circuit 96.

Although in the illustrated and described example, the subcooler circuit 96 includes two passes, any number of passes may be employed. For example, the refrigerant may take a single pass through the subcooler 78 or take more than two passes through the subcooler 78. By employing subcooler 78, heat transfer and refrigerant side pressure drop may be further optimized.

The foregoing description is only exemplary of the principles of the invention. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, but a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason, the following claims should be studied to determine the true spirit and scope of this invention.

Claims (21)

1. A microchannel heat exchanger, comprising:

a plurality of microchannel tubes including a first set of microchannel tubes and a second set of microchannel tubes;

a first circuit comprising a first plurality of microchannel tubes, wherein a portion of a first fluid flows through the first plurality of microchannel tubes and exchanges heat with a second fluid; and the number of the first and second groups,

a second circuit comprising a second set of microchannel tubes, wherein a remaining portion of the first fluid flows through the second set of microchannel tubes and exchanges heat with the second fluid, wherein the first fluid from the first circuit and the first fluid from the second circuit are combined into a common stream.

2. The microchannel heat exchanger as recited in claim 1 comprising a third circuit comprising a third set of microchannel tubes wherein the common stream flows through the third set of microchannel tubes to exchange heat with the second fluid.

3. The microchannel heat exchanger as set forth in claim 2 including a first header, a second header and a plurality of microchannel tubes extending therebetween,

wherein the first partition wall divides each of the first header and the second header into a first header section and a second header section, and the second partition wall divides each of the first header and the second header into a second header section and a third header section, preventing the first fluid from flowing between these header sections, and

wherein the first header section is associated with the first circuit, the second header section is associated with the second circuit, and the third header section is associated with the third circuit.

4. The microchannel heat exchanger as recited in claim 3 wherein the first header section, the second header section, and the third header section of the first header each comprise an additional wall that divides each of the header sections into an entry section and an exit section, wherein the first fluid enters each of the circuits through the entry section and exits each of the circuits through the exit section.

5. The microchannel heat exchanger as recited in claim 2 wherein,

the first fluid takes two passes through the plurality of microchannel tubes,

a portion of the first fluid flows through one set of the first plurality of microchannel tubes in a first direction and then flows through another set of the first plurality of microchannel tubes in a second, opposite direction,

the remainder of the first fluid flows through one set of the second set of microchannel tubes in a first direction and then flows through the other set of the second set of microchannel tubes in an opposite second direction, an

The common flow of the first fluid flows through one set of the third set of microchannel tubes in a first direction and then flows through the other set of the third set of microchannel tubes in a second, opposite direction.

6. The microchannel heat exchanger as recited in claim 2 wherein the first loop, the second loop, and the third loop are separate.

7. The microchannel heat exchanger as recited in claim 1 wherein the microchannel heat exchanger comprises a first header, a second header, and a plurality of microchannel tubes extending therebetween.

8. The microchannel heat exchanger as recited in claim 1 wherein the first fluid is refrigerant and the second fluid is air.

9. The microchannel heat exchanger as recited in claim 1 wherein the microchannel heat exchanger is one of a condenser and an evaporator.

10. The microchannel heat exchanger as recited in claim 1 wherein the first fluid obtains multiple passes through the plurality of microchannel tubes.

11. The microchannel heat exchanger as recited in claim 1 wherein the first fluid is divided equally between the first and second circuits.

12. The microchannel heat exchanger as recited in claim 1 wherein the plurality of microchannel tubes are substantially parallel.

13. A refrigeration system, comprising:

a compressor for compressing a refrigerant;

a condenser for cooling the refrigerant;

an expansion device for expanding the refrigerant; and the number of the first and second groups,

an evaporator for heating the refrigerant,

wherein at least one of the condenser and the evaporator is a microchannel heat exchanger comprising a plurality of microchannel tubes including a first batch of microchannel tubes and a second batch of microchannel tubes,

wherein a first circuit includes the first plurality of microchannel tubes and a second circuit includes the second plurality of microchannel tubes, a portion of the refrigerant flows through the first plurality of microchannel tubes and exchanges heat with air, a remaining portion of the refrigerant flows through the second plurality of microchannel tubes and exchanges heat with air, and the refrigerant from the first circuit and the refrigerant from the second circuit are combined into a common flow.

14. The refrigeration system of claim 13, comprising a third circuit comprising a third set of microchannel tubes, wherein a common flow flows through the third set of microchannel tubes to exchange heat with the air.

15. The refrigerant system as set forth in claim 14, including a first header, a second header and a plurality of microchannel tubes extending therebetween,

wherein the first partition wall divides each of the first header and the second header into a first header section and a second header section, and the second partition wall divides each of the first header and the second header into a second header section and a third header section, preventing refrigerant from flowing between these header sections, and

wherein the first header section is associated with the first circuit, the second header section is associated with the second circuit, and the third header section is associated with the third circuit.

16. The refrigeration system of claim 15, wherein the first, second and third header sections of a first header each include an additional wall dividing each of the header sections into an entry section through which the refrigerant enters each of the circuits and an exit section through which the refrigerant exits each of the circuits.

17. The refrigerant system as set forth in claim 14,

the refrigerant takes two passes through the plurality of microchannel tubes,

a portion of the refrigerant flows through one set of the first plurality of microchannel tubes in a first direction and then flows through another set of the first plurality of microchannel tubes in a second, opposite direction,

the remainder of the refrigerant flows through one of the second set of microchannel tubes in a first direction and then flows through the other of the second set of microchannel tubes in a second, opposite direction, an

The common flow of refrigerant flows through one set of the third plurality of microchannel tubes in a first direction and then flows through the other set of the third plurality of microchannel tubes in a second, opposite direction.

18. The refrigerant system as set forth in claim 14, wherein said first circuit, said second circuit and said third circuit are separate.

19. The refrigerant system as set forth in claim 13, wherein said microchannel heat exchanger includes a first header, a second header, and a plurality of microchannel tubes extending therebetween.

20. The refrigerant system as set forth in claim 13, wherein said refrigerant takes multiple passes through said plurality of microchannel tubes.

21. The refrigerant system as set forth in claim 13, wherein said refrigerant is divided equally between said first and second circuits.