Heat Exchanger with Fluid Expansion in Header
A heat exchanger includes a plurality of flat, multi-channel heat exchange tubes extending between spaced headers. Each heat exchange tube has a plurality of flow channels extending longitudinally in parallel relationship from its inlet end to its outlet end. A plurality of connectors are positioned between the inlet header and the heat transfer tubes such that the connector inlet ends are in fluid flow communication with the header through a relatively small cross-sectional flow area openings and the connector outlet ends are adapted to receive the inlet end of a heat exchanger tube. The connector defines a fluid flow pathway from the relatively small cross-sectional flow area opening in the inlet end of the connector to an outlet opening in the outlet end of the connector that opens to the flow channels of the heat exchange tube received in the outlet end of the connector.
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Reference is made to and this application claims priority from and the benefit of U.S. Provisional Application Ser. No. 60/649,269, filed Feb. 2, 2005, and entitled MINI-CHANNEL HEAT EXCHANGER WITH EXPANSION CONNECTOR, which application is incorporated herein in its entirety by reference.
FIELD OF THE INVENTIONThis invention relates generally to heat exchangers having a plurality of parallel tubes extending between a first header and a second header, also sometimes referred to as manifolds, and, more particularly, to providing fluid expansion within the header of a heat exchanger for improving distribution of two-phase flow through the parallel tubes of the heat exchanger, for example a heat exchanger in a refrigerant compression system.
BACKGROUND OF THE INVENTIONRefrigerant vapor compression systems are well known in the art. Air conditioners and heat pumps employing refrigerant vapor compression cycles are commonly used for cooling or cooling/heating air supplied to a climate controlled comfort zone within a residence, office building, hospital, school, restaurant or other facility. Refrigeration vapor compression systems are also commonly used for cooling air or other secondary fluid to provide a refrigerated environment for food items and beverage products within, for instance, display cases in supermarkets, convenience stores, groceries, cafeterias, restaurants and other food service establishments.
Conventionally, these refrigerant vapor compression systems include a compressor, a condenser, an expansion device, and an evaporator connected in refrigerant flow communication. The aforementioned basic refrigerant system components are interconnected by refrigerant lines in a closed refrigerant circuit and arranged in accord with the vapor compression cycle employed. An expansion device, commonly an expansion valve or a fixed-bore metering device, such as an orifice or a capillary tube, is disposed in the refrigerant line at a location in the refrigerant circuit upstream, with respect to refrigerant flow, of the evaporator and downstream of the condenser. The expansion device operates to expand the liquid refrigerant passing through the refrigerant line running from the condenser to the evaporator to a lower pressure and temperature. In doing so, a portion of the liquid refrigerant traversing the expansion device expands to vapor. As a result, in conventional refrigerant vapor compression systems of this type, the refrigerant flow entering the evaporator constitutes a two-phase mixture. The particular percentages of liquid refrigerant and vapor refrigerant depend upon the particular expansion device employed and the refrigerant in use, for example R12, R22, R134a, R404A, R410A, R407C, R717, R744 or other compressible fluid.
In some refrigerant vapor compression systems, the evaporator is a parallel tube heat exchanger. Such heat exchangers have a plurality of parallel refrigerant flow paths therethrough provided by a plurality of tubes extending in parallel relationship between an inlet header and an outlet header. The inlet header receives the refrigerant flow from the refrigerant circuit and distributes it amongst the plurality of flow paths through the heat exchanger. The outlet header serves to collect the refrigerant flow as it leaves the respective flow paths and to direct the collected flow back to the refrigerant line for a return to the compressor in a single pass heat exchanger or through an additional bank of heat exchange tubes in a multi-pass heat exchanger.
Historically, parallel tube heat exchangers used in such refrigerant compression systems have used round tubes, typically having a diameter of ½ inch, ⅜ inch or 7 millimeters. More recently, flat, rectangular or oval shape, multi-channel tubes are being used in heat exchangers for refrigerant vapor compression systems. Each multi-channel tube has a plurality of flow channels extending longitudinally in parallel relationship the length of the tube, each channel providing a small cross-sectional flow area refrigerant path. Thus, a heat exchanger with multi-channel tubes extending in parallel relationship between the inlet and outlet headers of the heat exchanger will have a relatively large number of small cross-sectional flow area refrigerant paths extending between the two headers. In contrast, a parallel tube heat exchanger with conventional round tubes will have a relatively small number of large flow area flow paths extending between the inlet and outlet headers.
Non-uniform distribution, also referred to as maldistibution, of two-phase refrigerant flow is a common problem in parallel tube heat exchangers which adversely impacts heat exchanger efficiency. Two-phase maldistribution problems are caused by the difference in density of the vapor phase refrigerant and the liquid phase refrigerant present in the inlet header due to the expansion of the refrigerant as it traversed the upstream expansion device.
One solution to control refrigeration flow distribution through parallel tubes in an evaporative heat exchanger is disclosed in U.S. Pat. No. 6,502,413, Repice et al. In the refrigerant vapor compression system disclosed therein, the high pressure liquid refrigerant from the condenser is partially expanded in a conventional in-line expansion device upstream of the heat exchanger inlet header to a lower pressure refrigerant. Additionally, a restriction, such as a simple narrowing in the tube or an internal orifice plate disposed within the tube, is provided in each tube connected to the inlet header downstream of the tube inlet to complete the expansion to a low pressure, liquid/vapor refrigerant mixture after entering the tube.
Another solution to control refrigeration flow distribution through parallel tubes in an evaporative heat exchanger is disclosed in Japanese Patent No. JP4080575, Kanzaki et al. In the refrigerant vapor compression system disclosed therein, the high pressure liquid refrigerant from the condenser is also partially expanded in a conventional in-line expansion device to a lower pressure refrigerant upstream of a distribution chamber of the heat exchanger. A plate having a plurality of orifices therein extends across the chamber. The lower pressure refrigerant expands as it passes through the orifices to a low pressure liquid/vapor mixture downstream of the plate and upstream of the inlets to the respective tubes opening to the chamber.
Japanese Patent No. 6241682, Massaki et al., discloses a parallel flow tube heat exchanger for a heat pump wherein the inlet end of each multichannel tube connecting to the inlet header is crushed to form a partial throttle restriction in each tube just downstream of the tube inlet. Japanese Patent No. JP8233409, Hiroaki et al., discloses a parallel flow tube heat exchanger wherein a plurality of flat, multi-channel tubes connect between a pair of headers, each of which has an interior which decreases in flow area in the direction of refrigerant flow as a means to uniformly distribute refrigerant to the respective tubes. Japanese Patent No. JP2002022313, Yasushi, discloses a parallel tube heat exchanger wherein refrigerant is supplied to the header through an inlet tube that extends along the axis of the header to terminate short of the end the header whereby the two phase refrigerant flow does not separate as it passes from the inlet tube into an annular channel between the outer surface of the inlet tube and the inside surface of the header. The two phase refrigerant flow thence passes into each of the tubes opening to the annular channel.
Obtaining uniform refrigerant flow distribution amongst the relatively large number of small cross-sectional flow area refrigerant flow paths is even more difficult than it is in conventional round tube heat exchangers and can significantly reduce heat exchanger efficiency.
SUMMARY OF THE INVENTIONIt is a general object of the invention to reduce maldistribution of fluid flow in a heat exchanger having a plurality of multi-channel tubes extending between a first header and a second header.
It is an object of one aspect of the invention to reduce maldistribution of refrigerant flow in a refrigerant vapor compression system heat exchanger having a plurality of multi-channel tubes extending between a first header and a second header.
It is an object of one aspect of the invention to distribute refrigerant to the individual channels of an array of multi-channel tubes in a relatively uniform manner.
It is an object of another aspect of the invention to provide for distribution and expansion of the refrigerant in a refrigerant vapor compression system heat exchanger having a plurality of multi-channel tubes as the refrigerant flow passes from a header to the individual channels of an array of multi-channel tubes.
In one aspect of the invention, a heat exchanger is provided having a header defining a chamber for receiving a fluid and at least one heat exchange tube having a plurality of fluid flow paths therethrough from an inlet end to an outlet end of the tube and having an inlet opening to the plurality of fluid flow paths. A connector has an inlet end in fluid flow communication with the chamber of the header through a first opening and an outlet end in fluid communication with the inlet opening of said at least one heat exchange tube through a second opening. The connector defines a fluid flow path extending from its inlet end to its outlet end. In an embodiment, the flow path through the connector may be divergent in the direction of fluid flow therethrough. The first opening has a relatively small flow area so as to provide a flow restriction through which fluid passes in flowing from the chamber of the header to the flow paths of the heat exchange tube.
In another aspect of the invention, a refrigerant vapor compression system includes a compressor, a condenser and an evaporative heat exchanger connected in refrigerant flow communication whereby high pressure refrigerant vapor passes from the compressor to the condenser, high pressure refrigerant liquid passes from the condenser to the evaporative heat exchanger, and low pressure refrigerant vapor passes from the evaporative heat exchanger to the compressor. The evaporative heat exchanger includes an inlet header and an outlet header, and a plurality of heat exchange tubes extending between the headers. The inlet header defines a chamber for receiving liquid refrigerant from a refrigerant circuit. Each heat exchange tube has an inlet end, an outlet end, and a plurality of fluid flow paths extending from an inlet opening at the inlet end to an outlet opening at the outlet end of the tube. A connector has an inlet end in fluid flow communication with the chamber of the inlet header through a first opening and has an outlet end in fluid flow communication through a second opening with the inlet opening of a heat exchange tube. The connector defines a fluid flow path extending from its inlet end to its outlet end. In an embodiment, the flow path through the connector may be divergent in the direction of fluid flow therethrough. The first opening has a relatively small cross-sectional flow area so as to provide a flow restriction through which fluid passes in flowing from the chamber of the header to the flow paths of the heat exchange tube.
BRIEF DESCRIPTION OF THE DRAWINGSFor a further understanding of these and objects of the invention, reference will be made to the following detailed description of the invention which is to be read in connection with the accompanying drawing, where:
The heat exchanger 10 of the invention will be described in general herein with reference to the illustrative single pass, parallel-tube embodiment of a multi-channel tube heat exchanger as depicted in
Referring now to
Each of the plurality of heat exchange tubes 40 of the heat exchanger 10 has its inlet end 43 inserted into a connector 50, rather than directly into the chamber 25 defined within the inlet header 20. Each connector 50 has an inlet end 52 and an outlet end 54 and defines a fluid flow path 55 extending from the inlet end 52 to the outlet end 54. The inlet end 52 is in fluid flow communication with the chamber 25 of the inlet header 20 through a first opening 51. The outlet end 54 is in fluid communication through a second opening 53 with the inlet openings 41 of the channels 42 at the inlet end of the associated heat transfer tube 40 received therein. The first opening 51 at the inlet end 52 of each connector 50 has a relatively small cross-sectional flow area. Therefore, the connectors 50 provide a plurality of flow restrictions, at least one associated with each heat transfer tube 40, that provide uniformity in pressure drop in the fluid flowing from the chamber 25 of the header 20 into the fluid flow path 55 within the connector 50, thereby ensuring a relatively uniform distribution of fluid amongst the individual tubes 40 operatively associated with the header 20.
In the embodiment depicted in
In the embodiment depicted in
In the embodiment depicted in
The fluid flow path 55 extending from the inlet opening 51 at the inlet end 52 of the connector 50 to the outlet opening 53 at the outlet end 54 of the connector 50 may, as best depicted in
Referring now to
In the embodiment depicted in
In the embodiment depicted in
Referring now to
Referring now to
While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the claims.
Claims
1. A heat exchanger comprising:
- a header defining a chamber for collecting a fluid; and
- at least one heat exchange tube defining a plurality of discrete fluid flow paths therethrough and having an inlet opening to said plurality of fluid flow paths; and
- a connector having an inlet end and an outlet end and defining a fluid flow path extending from said inlet end to said outlet end, said inlet end in fluid flow communication with the chamber of said header through a first opening and said outlet end in fluid communication with the inlet opening of said at least one heat exchange tube through a second opening, said first opening having a relatively small cross-sectional flow area.
2. A heat exchanger as recited in claim 1 wherein said first opening of said connector comprises an expansion orifice.
3. A heat exchanger as recited in claim 1 wherein the fluid flow path of said connector comprises a divergent fluid flow path expanding in cross-section in the direction of fluid flow therethrough from said first opening to said second opening.
4. A heat exchanger as recited in claim 3 wherein said first opening of said connector comprises an expansion orifice.
5. A heat exchanger as recited in claim 1 wherein said at least one heat exchange tube has a flattened, non-round cross-section.
6. A heat exchanger as recited in claim 5 wherein said at least one heat exchange tube has a flattened, rectangular cross-section.
7. A heat exchanger as recited in claim 5 wherein said at least one heat exchange tube has a flattened, generally oval cross-section.
8. A heat exchanger as recited in claim 1 wherein each of said plurality of channels defines a flow path having a non-circular cross-section.
9. A heat exchanger as recited in claim 8 wherein each of said plurality of channels defines a flow path is selected from a group of a rectangular, triangular or trapezoidal cross-section.
10. A heat exchanger as recited in claim 1 wherein each of said plurality of channels defines a flow path having a circular cross-section.
11. A heat exchanger as recited in claim 1 wherein said first opening comprises a plurality of openings.
12. A refrigerant vapor compression system comprising:
- a compressor, a condenser and an evaporative heat exchanger connected in fluid flow communication in a refrigerant circuit whereby high pressure refrigerant vapor passes from said compressor to said condenser, high pressure refrigerant passes from said condenser to said evaporative heat exchanger, and low pressure refrigerant vapor passes from said evaporative heat exchanger to said compressor; characterized in that said evaporative heat exchanger includes:
- an inlet header and an outlet header, each in fluid flow communication with the refrigerant circuit, said inlet header defining a chamber for receiving refrigerant from the refrigerant circuit;
- at least one heat exchange tube having an inlet opening and an outlet opening and having a plurality of discrete fluid flow paths extending from the inlet opening to the outlet opening, the outlet opening in fluid flow communication with said outlet header; and
- a connector having an inlet end and an outlet end and defining a fluid flow path extending from said inlet end to said outlet end, said inlet end in fluid flow communication with the chamber of said header through a first opening and said outlet end in fluid communication with the inlet opening of said at least one heat exchange tube through a second opening, said first opening having a relatively small flow area.
13. A refrigerant vapor compression system as recited in claim 12 wherein said first opening of said connector comprises an expansion orifice.
14. A refrigerant vapor compression system as recited in claim 12 wherein the fluid flow path of said connector comprises a divergent fluid flow path expanding in cross-section in the direction of fluid flow therethrough from said first opening to said second opening.
15. A refrigerant vapor compression system as recited in claim 14 wherein said first opening of said connector comprises an expansion orifice.
16. A refrigerant vapor compression system as recited in claim 12 wherein said at least one heat exchange tube has a flattened, non-round cross-section.
17. A refrigerant vapor compression system as recited in claim 16 wherein said at least one heat exchange tube has a flattened, rectangular cross-section.
18. A refrigerant vapor compression system as recited in claim 16 wherein said at least one heat exchange tube has a flattened, generally oval cross-section.
19. A refrigerant vapor compression system as recited in claim 12 wherein each of said plurality of channels defines a flow path having a non-circular cross-section.
20. A refrigerant vapor compression system as recited in claim 12 wherein each of said plurality of channels defines a flow path is selected from a group of a rectangular, triangular or trapezoidal cross-section.
21. A refrigerant vapor compression system as recited in claim 12 wherein each of said plurality of channels defines a flow path having a circular cross-section.
22. A refrigerant vapor compression system as recited in claim 12 wherein said heat exchanger comprises a single-pass heat exchanger.
23. A refrigerant vapor compression system as recited in claim 12 wherein said heat exchanger comprises a multi-pass heat exchanger.
24. A refrigerant vapor compression system as recited in claim 12 wherein said heat exchanger comprises a condenser.
25. A refrigerant vapor compression system as recited in claim 12 wherein said heat exchanger comprises an evaporator.
Type: Application
Filed: Dec 28, 2005
Publication Date: Apr 24, 2008
Applicant: Carrier Corporation (Farmington, CT)
Inventors: Mikhail Gorbounov (South Windsor, CT), Steven Lozyniak (South Windsor, CT), Parmesh Verma (Manchester, CT), Michael Taras (Fayetteville, NY), Robert Chopko (Baldwinsville, NY), Allen Kirkwood (Brownsburg, IN)
Application Number: 11/793,880
International Classification: F25B 1/00 (20060101); F28F 9/02 (20060101);