US20080190122A1

US20080190122A1 - Accumulator Integration with Heat Exchanger Header

Info

Publication number: US20080190122A1
Application number: US11/908,450
Authority: US
Inventors: Hans-Joachim Huff; Tobias H. Sienel; Yu Chen; Parmesh Verma
Original assignee: Carrier Comercial Refrigeration Inc
Current assignee: Taylor Commercial FoodService LLC
Priority date: 2005-03-18
Filing date: 2005-12-30
Publication date: 2008-08-14
Also published as: WO2006101569A3; EP1864059A2; WO2006101569A2; CN101203720A; JP2008533430A

Abstract

A refrigeration system includes a compressor for driving a refrigerant along a flow path in at least a first mode of system operation; a first heat exchanger along the flow path downstream of the compressor in the first mode; a second heat exchanger along the flow path upstream of the compressor in the first mode; and an expansion device in the flow path downstream of the first heat exchanger and upstream of the second heat exchanger in the first mode, wherein the second heat exchanger includes a combined header and accumulator for collecting liquid and vapor refrigerant.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of earlier filed Provisional Application Ser. No. 60/663,911 filed Mar. 18, 2005. Further, copending application docket 05-258-WO, entitled HIGH SIDE PRESSURE REGULATION FOR TRANSCRITICAL VAPOR COMPRESSION SYSTEM and filed on even date herewith, and the aforesaid Provisional Application Ser. No. 60/663,911 disclose prior art and inventive cooler systems. The disclosure of said application is incorporated by reference herein as if set forth at length.

BACKGROUND OF THE INVENTION

In many refrigeration applications space is a limited resource. Any reduction in space requirements for the refrigeration system application can improve the overall design of the system—either by reducing the overall size or by utilizing the space that becomes available for other purposes, such as increased heat exchanger area. Thus, a consolidated component design can reduce system cost and increase system performance.
FIG. 1 shows a prior art vapor compression system having a compressor 1, a gas cooler 2, an expansion device 3, and an evaporator 4. In evaporator 4, refrigerant passes through a series of heat exchanger tubes 5 in a heat exchange relationship with air being cooled as desired. Refrigerants typically enters tubes 5 through a header 6 and exits tubes 5 into a header 7. Refrigerant collected in header 7 then flows to an accumulator 8 where liquid phase refrigerant and oil separate from vapor phase refrigerant, and vapor is drawn back to compressor 1.
While the system illustrated in FIG. 1 is functional, as set forth above, a functional system which occupies less space is desirable.
It is therefore the primary object of the present invention to provide such a system.
Other objects and advantages will appear herein.

SUMMARY OF THE INVENTION

A refrigeration system is provided which includes a compressor for driving a refrigerant along a flow path in at least a first mode of system operation; a first heat exchanger along the flow path downstream of the compressor in the first mode; a second heat exchanger along the flow path upstream of the compressor in the first mode; and an expansion device in the flow path downstream of the first heat exchanger and upstream of the second heat exchanger in the first mode, wherein the second heat exchanger includes a combined header and accumulator for collecting liquid and vapor refrigerant. The combined header and accumulator serves to conserve space which is particularly advantageous, for example in transcritical vapor compression systems.
A method is also provided for operating a refrigeration system in accordance with the present invention, which method comprises operating a compressor to drive a refrigerant along a flow path, sequentially, to a first heat exchanger, an expansion device, a second heat exchanger, a combined header and accumulator, and back to the compressor, wherein flow is directly from the second heat exchanger to the combined header and accumulator, and wherein flow is directly from the combined header and accumulator to the compressor.

BRIEF DESCRIPTION OF THE DRAWING

A detailed description of preferred embodiments of the present invention follows, with reference to the attached drawings, wherein:

FIG. 1 is an illustration of a prior art vapor compression system;

FIG. 2 is a schematic illustration of a system having a combined accumulator and header according to the invention;

FIG. 3 is a schematic illustration of an alternative embodiment of the combined accumulator and header according to the invention; and

FIG. 4 is a schematic illustration of a further alternative embodiment of the combined accumulator and header in accordance with the present invention.

DETAILED DESCRIPTION

The invention relates to a heat exchanger configuration for a vapor compression system and, more particularly, to a space-saving combination of the refrigerant accumulator and the heat exchanger header in a transcritical vapor compression cycle. In transcritical vapor compression systems, heat rejection occurs at a pressure above the critical pressure of the refrigerant. During the heat rejection the refrigerant does not condense. The charge management in a transcritical system is usually accomplished by adding an accumulator to the evaporator outlet, following an outlet header (See FIG. 1).
FIG. 2 shows the vapor compression system 10 in accordance with the present invention which includes a compressor 12, a first heat exchanger or gas cooler 14, an expansion device 16 and a second heat exchanger or evaporator 18. As compared to FIG. 1, it should be readily appreciated that evaporator 18 includes an inlet header 20 as in conventional devices, but that evaporator 18 also includes a combined header and accumulator 22 which combines the functions of separate outlet header 7 and accumulator 8 as illustrated in FIG. 1. This advantageously allows for conservation of space while providing the desired functions of both the header and the accumulator of this device.
As shown in FIG. 2, combined header and accumulator 22 in accordance with the present invention is a single chamber which defines a lower liquid refrigerant zone 24 and an upper vapor refrigerant zone 26. Flow enters the combined header and accumulator 22 directly from tubes 28 of second heat exchanger 18. In this regard, it is noted that FIG. 2 shows lower liquid refrigerant zone 24 defined at a location which is lower than the inlet from the lower most tube 30. This advantageously prevents masking and/or back-flow of liquid refrigerant with respect to lower most tube 30. As shown in FIG. 2, this chamber is defined by side, front, back, top and bottom walls around the end of the heat exchanger tubes.
Also as shown in FIG. 2, combined header and accumulator 22 advantageously has an inner conduit 32 which extends from a bottom surface of combined accumulator and header 22 upwardly above the expected liquid level of liquid within lower liquid refrigerant zone 24. Compressor 12 draws vapor phase refrigerant out of vapor refrigerant zone 26 and through conduit 32 to the compressor suction line.
A lower portion 34 of conduit 32 is preferably provided with a pin hole 36 which advantageously allows oil within the lower liquid refrigerant zone 24 to be drawn back to compressor 12 as desired.
The heat exchangers 14, 18 of the present invention can be provided as any known type of heat exchanger, preferably as refrigerant-air heat exchangers. Specific examples of suitable heat exchangers include but are not limited to wire on tube heat exchangers, fin heat exchangers, and the like.
The system of the present invention is particularly well suited to a transcritical vapor compression system, for example, a system which uses CO₂as working fluid. Of course, other refrigerants, particularly those with similar properties to CO₂under expected operating conditions, can be used and are considered to be well within the broad scope of the present invention.
Expansion device 16 can be any suitable expansion device known to a person of skill in the art. A pressure regulator, for example a pressure regulator such as that disclosed in commonly owned and simultaneously filed PCT Application bearing attorney docket number 05-258-WO and entitled HIGH SIDE PRESSURE REGULATION FOR TRANSCRITICAL VAPOR COMPRESSION SYSTEM, is also well within the scope of the present invention and is considered to be an expansion device as used herein.
Header and accumulator 22 can advantageously be incorporated into heat exchanger 18 as shown in FIG. 2. Alternatively, header and accumulator 22 can be a separate structure defining a chamber and communicated with heat exchanger 18, preferably through direct flow from tubes of the heat exchanger into the chamber.
FIG. 3 shows a further alternative embodiment of the present invention, having the same basic components as the embodiment of FIG. 2. In the embodiment of FIG. 3, evaporator 18 is divided into two components 38, 40, and combined header and accumulator 22 is connected to each component 38, 40 through a short flow conduit 42. In this embodiment, it should be noted that by positioning lower most tube 30 sufficiently high on second heat exchanger 18, the lower liquid refrigerant zone 24 can be defined within combined accumulator and header 22 so that a bottom surface 44 of combined accumulator and header 22 does not extend substantially beyond a bottom surface 46 of second heat exchanger 18. Conduit 42 is preferably very short, most preferably having a length of less than about 5 inches.
FIG. 4 shows a further embodiment of the present invention, wherein system 10 includes the same components as those described in connection with FIGS. 2 and 3. With the embodiment of FIG. 4, refrigerant fed from expansion device 16 to evaporator 18 flows through a single conduit 48 to combined header and accumulator 22 in accordance with the present invention. From this point, vapor phase refrigerant is drawn back to compressor 12 as desired.
Embodiments of the invention as indicated in FIGS. 2-4 of the present invention integrate the accumulator and the evaporator outlet header into a single chamber. This single chamber performs the function of both the header and accumulator of the conventional system of FIG. 1. Advantageously, the functions normally performed in the separate header and accumulator are now performed in the same space. This design reduces the space requirements for the accumulator as well as the overall tubing length and the number of tube connections.
Two-phase flow leaving the evaporator is separated in the header. The liquid refrigerant is collected by gravity at the bottom of the accumulator-header. The vapor leaves the accumulator header through the tube inserted into the header. The tube has a pin-hole in the accumulator section of the header to allow oil return to the compressor.
One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, when implemented as a remanufacturing of an existing system or reengineering of an existing system configuration, details of the existing configuration may influence details of the implementation. Accordingly, other embodiments are within the scope of the following claims.

Claims

1. A refrigeration system comprising:

a compressor for driving a refrigerant along a flow path in at least a first mode of system operation;

a first heat exchanger along the flow path downstream of the compressor in the first mode;

a second heat exchanger along the flow path upstream of the compressor in the first mode; and

an expansion device in the flow path downstream of the first heat exchanger and upstream of the second heat exchanger in the first mode,

wherein the second heat exchanger includes a combined header and accumulator for collecting liquid and vapor refrigerant.

2. The system of claim 1 wherein the combined header and accumulator comprises a chamber communicated with refrigerant flow paths of the second heat exchanger for receiving two phase refrigerant flow and defining therein a lower liquid refrigerant zone and an upper vapor refrigerant zone.

3. The system of claim 2, wherein the lower liquid refrigerant zone is defined below a lower most flow port between the second heat exchanger and the combined header and accumulator.

4. The system of claim 3, wherein the lower most flow port is positioned high enough above the lower liquid refrigerant zone that the lower liquid refrigerant zone does not extend beyond the evaporator.

5. The system of claim 1, wherein tubes of the second heat exchanger flow directly into the combined header and accumulator.

6. The system of claim 5, wherein a vapor flow line is connected directly from the combined header and accumulator to the compressor.

7. The system of claim 2 further comprising a conduit communicated with the upper vapor refrigerant zone for conveying vapor refrigerant to the compressor.

8. The system of claim 7, wherein the conduit extends upwardly through the liquid refrigerant zone into the vapor refrigerant zone, and is also communicated with the liquid refrigerant zone.

9. The system of claim 8, wherein the conduit is communicated with the liquid refrigerant zone through a pin-hole to allow oil to return to the compressor.

10. The system of claim 1 wherein:

the refrigerant comprises, a transcritical vapor system refrigerant and wherein

the first and second heat exchangers are refrigerant-air heat exchangers.

11. A beverage cooling device comprising the system of claim 1.

12. A method for operating a refrigeration system comprising operating a compressor to drive a refrigerant along a flow path, sequentially, to a first heat exchanger, an expansion device, a second heat exchanger, a combined header and accumulator, and back to the compressor, wherein flow is directly from the second heat exchanger to the combined header and accumulator, and wherein flow is directly from the combined header and accumulator to the compressor.

13. The method of claim 12, wherein the second heat exchanger comprises a flow tube, wherein operation of the compressor creates two-phase refrigerant in the flow tube, and wherein the two-phase refrigerant flows directly to the combined header and accumulator.

14. The method of claim 12, wherein the refrigerant is a transcritical vapor system refrigerant.

15. The method of claim 12, wherein the refrigerant is CO₂.

16. The method of claim 12, wherein the combined header and accumulator defines a lower liquid refrigerant zone and an upper vapor refrigerant zone, and wherein flow of refrigerant into the combined header and accumulator causes separation of the refrigerant into a liquid refrigerant in the lower liquid refrigerant zone and vapor refrigerant in the upper vapor refrigerant zone.