US20080078198A1

US20080078198A1 - Microchannel heat exchanger

Info

Publication number: US20080078198A1
Application number: US11/863,677
Authority: US
Inventors: Peter James Breiding; Cosimo Caronna
Original assignee: Johnson Controls Technology Co
Current assignee: Johnson Controls Technology Co
Priority date: 2006-09-28
Filing date: 2007-09-28
Publication date: 2008-04-03
Also published as: WO2008042368A1; CN101517349A

Abstract

A microchannel heat exchanger is provided that is configured to drain condensate out of the microchannel heat exchanger. The microchannel heat exchanger has tube sections that are positioned at an angle with respect to a horizontal plane when the microchannel heat exchanger has a vertical orientation. The fins between the tube sections can be positioned perpendicular to the angled tube sections or can be positioned perpendicular to the horizontal plane.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/827,387 filed on Sep. 28, 2006, which Application is hereby incorporated by reference.

BACKGROUND

The application generally relates to microchannel heat exchangers. The application relates more specifically to the drainage of condensate from microchannel heat exchangers.
In a typical microchannel heat exchanger or coil slab, a series of tube sections are connected (physically and thermally) by fins that are configured to permit airflow through the heat exchanger in order to provide for heat transfer between the airflow and a circulating fluid, e.g., water or refrigerant. The tube sections of the heat exchanger are oriented to extend horizontally (but can be oriented vertically) and each tube section has several tubes or channels that are used to circulate the fluid. The outside of the tube section is a continuous surface typically having a rectangular shape. The continuous surface of the tube sections provides a place for moisture to be trapped on the top surface of the tube sections between the connecting fins.
The collection or trapping of moisture on the top surface of the horizontally oriented tube sections severely limits the use of microchannel heat exchangers in heat pump applications. In a heat pump application, the outdoor coil serves as the evaporator when the heat pump is operating in a heating mode. When operating as an evaporator, the outdoor coil is removing heat and moisture from the outdoor air. The removed moisture may then collect on the top surface of the tube sections and decrease system performance by reducing the airflow through the heat exchanger as a result of a greater pressure drop. This moisture may also freeze under certain conditions, further reducing the airflow through the heat exchanger and thereby lowering the efficiency and capacity of the system.
Some techniques to attempt to reduce the amount of moisture collecting on the top surface of the tube sections include the application of hydrophilic coatings to the surfaces of the heat exchanger and the slanting of the entire heat exchanger. The use of hydrophilic coatings has many drawbacks including increased costs (for both the coating and its application) and greater susceptibility to damage and performance degradation. Furthermore, the slanting of the entire heat exchanger has not been shown to increase condensate drainage and results in significant manufacturing issues and costs from having to interconnect individual coil slabs.
Intended advantages of the disclosed systems and/or methods satisfy one or more of these needs or provides other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the claims, regardless of whether they accomplish one or more of the aforementioned needs.

SUMMARY

One embodiment relates to a microchannel heat exchanger having first and second support members, a plurality of tube sections disposed between the first and second support members, and a plurality of fins disposed between the plurality of tube sections. The first and second support members are disposed substantially parallel to each other. Each tube section of the plurality of tube sections has a plurality of tubes to circulate a fluid. The plurality of tube sections are positioned at a predetermined angle with respect to the first and second support members.
Another embodiment relates to an outdoor unit for an air conditioning or heat pump system having a compressor to compress a refrigerant for the system, a fan configured and disposed to circulate air through the outdoor unit, and a microchannel heat exchanger. The microchannel heat exchanger includes at least one support member, a plurality of tube sections disposed adjacent to the at least one support member, and a plurality of fins disposed between the plurality of tube sections. Each tube section of the plurality of tube sections has a plurality of tubes to circulate a fluid. The plurality of tube sections are positioned at a predetermined angle with respect to the at least one support member.
A further embodiment relates to a microchannel heat exchanger having a plurality of tubes extending substantially horizontally and disposed substantially parallel to one another, a plurality of fins disposed between the plurality of tubes, and at least one header configured and disposed to distribute fluid to the plurality of tubes. Each tube of the plurality of tubes has a plurality of channels to circulate a fluid. The plurality of tubes are positioned at a predetermined angle with respect to a horizontal plane. The plurality of tubes, the plurality of fins and the at least one header are oriented substantially vertically with respect to each other.
Certain advantages of the embodiments described herein are improved condensate drainage from the microchannel heat exchanger while maintaining a single slab design, and potentially increased airflow through the microchannel heat exchanger.
Alternative exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a schematic illustration of a refrigeration system.

FIG. 1B is a schematic illustration of a heat pump system.

FIG. 2 is partial cross-sectional view of an outdoor unit used in a heat pump system.

FIG. 3 is a schematic end view of one embodiment of a drainage configuration for a microchannel heat exchanger.

FIG. 4 is a partial side view of the embodiment of the microchannel heat exchanger of FIG. 3.

FIG. 5 is a schematic end view of another embodiment of a drainage configuration for a microchannel heat exchanger.

FIG. 6 is an isometric view of the embodiment of the microchannel heat exchanger of FIG. 5.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

In FIGS. 1A and 1B, a heating, ventilation, air conditioning and refrigeration (HVAC&R) system 100 includes a compressor 102, a condenser 104, an evaporator 106, and a control panel 108 (FIG. 1A) or a compressor 102, a reversing valve 150, an indoor unit 154, an outdoor unit 152 and a control panel 108 (FIG. 1B). Circulating through system 100 is a refrigerant. Some examples of refrigerants that may be used in system 100 are hydrofluorocarbon (HFC) based refrigerants, e.g., R-410A, R-407, R-134a, carbon dioxide, CO₂, (R-744), ammonia, NH₃, (R-717), and any other suitable type of refrigerant. The HVAC&R system 100 may include many other features that are not shown in FIGS. 1A and 1B.
System 100 can be operated as an air conditioning only system, where evaporator 106 is located indoors, i.e., as indoor unit 154, to provide cooling to the indoor air and condenser 104 is preferably located outdoors, i.e., as outdoor unit 152, to discharge heat to the outdoor air. System 100 can also be operated as a heat pump system with the inclusion of reversing valve 150 to control and direct the flow of refrigerant from compressor 102. When the heat pump is operated in an air conditioning mode, reversing valve 150 is controlled for refrigerant flow as described above for an air conditioning system. However, when the heat pump is operated in a heating mode, the flow of the refrigerant is in the opposite direction from the air conditioning mode and condenser 104 is preferably located indoors, i.e., as indoor unit 154, to provide heating of the indoor air and evaporator 106 is preferably located outdoors, i.e., as outdoor unit 152, to absorb heat from the outdoor air.
Compressor 102 compresses a refrigerant vapor and delivers the vapor to condenser 104 through a discharge line (and reversing valve 150 if operated as a heat pump). Compressor 102 can be a screw compressor, reciprocating compressor, centrifugal compressor, rotary compressor, swing link compressor, scroll compressor, turbine compressor, or any other suitable compressor. The refrigerant vapor delivered by compressor 102 to condenser 104 enters into a heat exchange relationship with a fluid, e.g., air, and undergoes a phase change to a refrigerant liquid as a result of the heat exchange relationship with the fluid. The condensed liquid refrigerant from condenser 104 flows through an expansion device 110 to evaporator 106.
The condensed liquid refrigerant delivered to evaporator 106 enters into a heat exchange relationship with a fluid, e.g., air, and undergoes a phase change to a refrigerant vapor as a result of the heat exchange relationship with the fluid. The vapor refrigerant in evaporator 106 exits evaporator 106 and returns to compressor 102 by a suction line to complete the cycle (and reversing valve 150 if operated as a heat pump).
Compressor 102 of system 100, whether operated as a heat pump or as an air conditioner, is driven by a motor or drive mechanism 120. Motor 120 can be powered by a variable speed drive (VSD) or can be powered directly from an AC or DC power source. The VSD, if used, receives AC power having a particular fixed line voltage and fixed line frequency from the AC power source and provides power to motor 120 having a variable voltage and frequency. Motor 120 used in system 100 can be any type of electric motor that can be powered by a VSD or directly from an AC or DC power source. For example, motor 120 can be a switched reluctance (SR) motor, an induction motor, an electronically commutated permanent magnet motor (ECM), or any other suitable motor type.
Control panel 108 can include an analog to digital (A/D) converter, a microprocessor, a non-volatile memory, and an interface board to control operation of the HVAC&R system 100. Control panel 108 can execute a control algorithm(s) to control operation of system 100. While the control algorithm can be embodied in a computer program(s) and executed by the microprocessor, it is to be understood that the control algorithm may be implemented and executed using digital and/or analog hardware by those skilled in the art. If hardware is used to execute the control algorithm, the corresponding configuration of control panel 108 can be changed to incorporate the necessary components and to remove any components that may no longer be required.
In one embodiment, condenser 104 and/or evaporator 106 can include one or more microchannel heat exchangers or coil slabs. The microchannel heat exchanger circulates refrigerant through two or more tube sections, each of which has two more tubes, passageways or microchannels for the flow of refrigerant (see e.g., FIGS. 3 and 5). The tube section can have a cross-sectional shape in the form or a rectangle, parallelogram, trapezoid, ellipse, oval or other similar geometric shape. The tubes in the tube section can have a cross-sectional shape in the form of a rectangle, square, circle, oval, ellipse, triangle, trapezoid, parallelogram or other suitable geometric shape. In one embodiment, the tubes in the tube section can have a size, e.g., width or diameter, of between about a half (0.5) millimeter (mm) to about a three (3) millimeters (mm). In another embodiment, the tubes in the tube section can have a size, e.g., width or diameter, of about one (1) millimeter (mm).
Connected between the tube sections are two or more fins or fin sections. In one embodiment, the fins can be arranged to extend substantially perpendicular to the flow of refrigerant in the tube sections. However, in another embodiment, the fins can be arranged to extend substantially parallel to the flow of refrigerant in the tube sections. The fins can be louvered fins, corrugated fins or any other suitable type of fin. Finally, any suitable distribution system or header can be used to distribute the refrigerant in the tubes.
In FIG. 2, outdoor unit 152 can include a heat exchanger or coil slab 202 that provides for the exchange of heat between the refrigerant circulating in heat exchanger 202 and the outdoor air. To assist in the transfer of heat in heat exchanger 202, a fan 204 can be used to circulate the outdoor air through heat exchanger 202. The fan 204 can be configured to circulate the outdoor air by either pushing or pulling the outdoor air through heat exchanger 202.
FIGS. 3-6 show embodiments of heat exchanger 202 as a microchannel heat exchanger or coil slab that is oriented substantially vertically. The substantially vertical orientation of microchannel heat exchanger 202 permits microchannel heat exchanger 202 to be manufactured as a single heat exchanger or coil slab.
In FIGS. 3 and 4, an exemplary embodiment of microchannel heat exchanger 202 includes support members 308 at the top and bottom of microchannel heat exchanger 202. Support members 308 are substantially parallel to one another and are arranged to provide the substantial vertical orientation of microchannel heat exchanger 202. In addition, microchannel heat exchanger 202 includes two or more tube sections 302 that extend substantially horizontally between top and bottom support members 308. Tube sections 302 can be connected to one or more distribution systems or headers for the distribution of refrigerant in tube sections 302. Each tube section 302 has two or more tubes, passageways or microchannels 304 for the flow or circulation of refrigerant through microchannel heat exchanger 202. The tube section 302 can have a cross-sectional shape in the form or a rectangle, parallelogram, trapezoid, ellipse, oval or other similar geometric shape. The tubes 304 in tube section 302 can have a cross-sectional shape in the form of a rectangle, square, circle, oval, ellipse, triangle, trapezoid, parallelogram or other suitable geometric shape. In one embodiment, the tubes 304 in tube section 302 can have a size, e.g., width or diameter, of between about a half (0.5) millimeter (mm) to about a three (3) millimeters (mm). In another embodiment, the tubes 304 in tube section 302 can have a size, e.g., width or diameter, of about one (1) millimeter (mm).
Tube sections 302 in FIGS. 3 and 4 are positioned substantially parallel to one another and at an angle (A) with respect to support members 308. The positioning of tube sections 302 at the angle (A) facilitates the drainage of condensation from microchannel heat exchanger 202 and can prevent the accumulation of condensation on the top surfaces of tube sections 302. In one embodiment, the angle (A) can be between about three (3) degrees and about forty-five (45) degrees. In another embodiment, the angle (A) can be about fifteen (15) degrees.
Connected between tube sections 302 are two or more fins or fin sections 306. Fins 306 can be arranged to extend substantially parallel to the flow of refrigerant in the tube sections 302. In addition, fins 306 can be positioned to be substantially perpendicular to the support members 308 when viewed in cross-section as shown in FIG. 3. To be able to position fins 306 substantially perpendicular to support members 308, fins 306 have to be manufactured to have a substantially parallelogram shaped outline or cross-section. This substantially parallelogram shaped outline or cross-section of fin 306, permits fin 306 to be in contact with the entire width of both surrounding tube sections 302. The fins 306 can be louvered fins, corrugated fins or any other suitable type of fine. Furthermore, with the positioning of fins 306 substantially perpendicular to support members 308, any corresponding vertical louvers located in fins 306 (as shown in FIG. 3) would also be substantially perpendicular to support members 308. Finally, as a result of tube sections 302 being angled with respect to the support members 308, there is a space between tube sections 302 and support members 308. This space can remain open, can be used for additional support members, or can be used for additional fins.
In FIGS. 5 and 6, another embodiment of microchannel heat exchanger 202 includes support members 318 at the top and bottom of microchannel heat exchanger 202. Support members 318 are substantially parallel to one another and are arranged to provide the substantial vertical orientation of microchannel heat exchanger 202. In addition, microchannel heat exchanger 202 includes two or more tube sections 312 that extend substantially horizontally between top and bottom support members 318. Tube sections 312 can be connected to one or more distribution systems or headers for the distribution of refrigerant therein (as shown in FIG. 6). Each tube section 312 has two or more tubes, passageways or microchannels 314 for the flow or circulation of refrigerant through microchannel heat exchanger 202. Tube section 312 can have a cross-sectional shape in the form or a rectangle, parallelogram, trapezoid, ellipse, oval or other similar geometric shape. The tubes 314 in tube section 312 can have a cross-sectional shape in the form of a rectangle, square, circle, oval, ellipse, triangle, trapezoid, parallelogram or other suitable geometric shape. In one embodiment, the tubes 314 in the tube section 312 can have a size, e.g., width or diameter, of between about a half (0.5) millimeter (mm) to about a three (3) millimeters (mm). In another embodiment, the tubes 314 in tube section 312 can have a size, e.g., width or diameter, of about one (1) millimeter (mm).
Tube sections 312 in FIGS. 5 and 6 are positioned substantially parallel to one another and at an angle (B) with respect to support members 318. The positioning of tube sections 312 at the angle (B) facilitates the drainage of condensation from microchannel heat exchanger 202 and can prevent the accumulation of condensation on the top surfaces of tube sections 312. In one embodiment, the angle (B) can be between about three (3) degrees and about forty-five (45) degrees. In another embodiment, the angle (B) can be about fifteen (15) degrees.
Connected between tube sections 312 are two or more fins or fin sections 316. Fins 316 can be arranged to extend substantially parallel to the flow of refrigerant in tube sections 312. In addition, fins 316 can be positioned to be substantially perpendicular to tube sections 312 when viewed in cross-section as shown in FIG. 5. To obtain the substantially perpendicular orientation of fins 316 with respect to the tube sections 312, fins 316 can be manufactured as is known in the art and then angled at the same angle as the tube sections 312. The fins 316 can be louvered fins, corrugated fins or any other suitable type of fin. Furthermore, with the positioning of fins 316 substantially perpendicular to tube sections 312, any corresponding vertical louvers located in fins 316 (as shown in FIG. 5) would also be substantially perpendicular to tube sections 312. Finally, as a result of tube sections 312 being angled with respect to the support members 318, there is a space between tube sections 312 and support members 318. This space can remain open, can be used for additional support members, or can be used for additional fins.
Tube sections 302, 312 in the embodiments of FIGS. 3-6 can be angled such that the drainage of the condensation from microchannel heat exchanger 202 is out of outdoor unit 152, i.e., away from compressor 102. However, tube sections 302, 312 in the embodiments of FIGS. 3-6 can also be angled such that the drainage of the condensation from microchannel heat exchanger 202 is into outdoor unit 152, i.e., toward compressor 102. When draining the condensate into the outdoor unit 152, an additional drainage system may be needed to remove the condensate from the interior of the outdoor unit 152.
In another embodiment, the fins of the microchannel heat exchanger can be arranged to extend substantially perpendicular to the tube sections. Each perpendicularly extending fin can have a plurality of apertures arranged at the same angle as is desired for the corresponding tube sections. Then, when the microchannel heat exchanger is assembled, the tube sections are angled to permit drainage of condensation from the microchannel heat exchanger.
In a further embodiment, the microchannel heat exchanger can be made without either or both of the top and bottom support members. The connection of the header(s) to the tube sections in the microchannel heat exchanger may provide the necessary support and rigidity for the microchannel heat exchanger to be able to remove the support members.
While microchannel heat exchanger 202 has been described for use in outdoor unit 152, it is to be understood that microchannel heat exchanger 202 can also be used for indoor unit 154. By using the same heat exchanger for both indoor unit 154 and the outdoor unit 152, only one type of heat exchanger has to be provided and indoor unit 154 can benefit from the advantages of the microchannel heat exchanger 202.
It should be understood that the application is not limited to the details or methodology set forth in the following description or illustrated in the figures. It should also be understood that the phraseology and terminology employed herein is for the purpose of description only and should not be regarded as limiting.
While the exemplary embodiments illustrated in the figures and described herein are presently preferred, it should be understood that these embodiments are offered by way of example only. Accordingly, the present application is not limited to a particular embodiment, but extends to various modifications that nevertheless fall within the scope of the appended claims. The order or sequence of any processes or method steps may be varied or re-sequenced according to alternative embodiments.
It is important to note that the construction and arrangement of the microchannel heat exchanger as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present application. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present application.

Claims

1. A microchannel heat exchanger comprising:

first and second support members, the first and second support members being disposed substantially parallel to each other;

a plurality of tube sections disposed between the first and second support members, each tube section of the plurality of tube sections having a plurality of tubes to circulate a fluid;

a plurality of fins disposed between the plurality of tube sections; and

wherein the plurality of tube sections are positioned at a predetermined angle with respect to the first and second support members.

2. The microchannel heat exchanger of claim 1 wherein the predetermined angle is between about 3 degrees and about 45 degrees.

3. The microchannel heat exchanger of claim 2 wherein the predetermined angle is about 15 degrees.

4. The microchannel heat exchanger of claim 1 wherein the plurality of fins are oriented substantially perpendicular to the plurality of tube sections.

5. The microchannel heat exchanger of claim 1 wherein the plurality of fins are oriented substantially perpendicular to the first and second support members.

6. The microchannel heat exchanger of claim 1 wherein the position of the plurality of tube sections at the predetermined angle permits drainage of condensate from the microchannel heat exchanger.

7. The microchannel heat exchanger of claim 1 wherein the first and second support members, the plurality of tube sections and the plurality of fins are oriented substantially vertically with respect to each other.

8. An outdoor unit for an air conditioning or heat pump system comprising:

a compressor to compress a refrigerant for the system;

a fan configured and disposed to circulate air through the outdoor unit; and

a microchannel heat exchanger, the microchannel heat exchanger comprising:

at least one support member extending substantially horizontally;

a plurality of tube sections disposed adjacent to the at least one support member, each tube section of the plurality of tube sections having a plurality of tubes to circulate a fluid;

a plurality of fins disposed between the plurality of tube sections; and

wherein the plurality of tube sections are positioned at a predetermined angle with respect to the at least one support member.

9. The outdoor unit of claim 8 wherein the predetermined angle is between about 3 degrees and about 45 degrees.

10. The outdoor unit of claim 9 wherein the predetermined angle is about 15 degrees.

11. The outdoor unit of claim 8 wherein the plurality of fins are oriented substantially perpendicular to the plurality of tube sections.

12. The outdoor unit of claim 8 wherein the plurality of fins are oriented substantially perpendicular to the at least one support member.

13. The outdoor unit of claim 8 wherein the position of the plurality of tube sections at the predetermined angle permits drainage of condensate from the microchannel heat exchanger.

14. The outdoor unit of claim 8 wherein the at lest one support member, the plurality of tube sections and the plurality of fins are oriented substantially vertically with respect to each other.

15. A microchannel heat exchanger comprising:

a plurality of tubes extending substantially horizontally and disposed substantially parallel to one another, each tube of the plurality of tubes having a plurality of channels to circulate a fluid;

a plurality of fins disposed between the plurality of tubes;

at least one header configured and disposed to distribute fluid to the plurality of tubes;

the plurality of tubes are positioned at a predetermined angle with respect to a horizontal plane; and

wherein the plurality of tubes, the plurality of fins and the at least one header are oriented substantially vertically with respect to each other.

16. The microchannel heat exchanger of claim 15 wherein the plurality of fins are oriented substantially perpendicular to the plurality of tubes.

17. The microchannel heat exchanger of claim 15 wherein the plurality of fins are oriented substantially perpendicular to the horizontal plane.

18. The microchannel heat exchanger of claim 15 wherein the position of the plurality of tubes at the predetermined angle permits drainage of condensate from the microchannel heat exchanger.

19. The microchannel heat exchanger of claim 15 wherein the predetermined angle is between about 3 degrees and about 45 degrees.

20. The microchannel heat exchanger of claim 19 wherein the predetermined angle is about 15 degrees.