US20080190134A1

US20080190134A1 - Refrigerant flow distributor

Info

Publication number: US20080190134A1
Application number: US11/947,217
Authority: US
Inventors: Nazih M. Khatib; Michael W. Trumbower
Original assignee: Parker Hannifin Corp
Current assignee: Parker Hannifin Corp
Priority date: 2006-11-29
Filing date: 2007-11-29
Publication date: 2008-08-14

Abstract

A flow distributor for directing flow into a parallel-flow micro-channel heat exchanger header pipe, the flow distributor utilizing a nozzle and a mixing chamber to provide an even mix of a two phase refrigerant, and a plurality of outlets which provide a means for distributing two-phase liquid-gas refrigerant evenly along the length of the header pipe.

Description

CROSS-REFERENCE TO RELATED CASES

This application claims the benefit of U.S. Provisional Application Ser. No. 60/861,655; filed Nov. 29, 2006, the disclosure of which is expressly incorporated herein by reference.

TECHNICAL FIELD

This invention relates to a flow distributor for evenly mixing and distributing two-phase liquid-gas refrigerant directing flow into a parallel-flow micro-channel heat exchanger header pipe.

BACKGROUND

A heatpump system (i.e., a refrigerant system) can be used to control the temperature of a certain medium such as, for example, the air inside of a building or automobile. A heatpump system generally comprises an evaporating heat exchanger (e.g., an evaporator), a compressor, a condensing heat exchanger (e.g., a condenser), a metering device (e.g., a metering/expansion valve), and a series of lines (e.g., pipes, tubes, ducts) connecting these components together so that refrigerant fluid can cycle therethrough.
In a heatpump system, refrigerant fluid enters the evaporating heat exchanger as a low pressure and low temperature vapor-liquid. As the vapor-liquid passes through the evaporator, it is boiled into a low pressure gas state. The fluid from the evaporator is drawn through the compressor, which increases the pressure and temperature of the gas. From the compressor, the high pressure and high temperature gas passes through the condensing heat exchanger whereat it is condensed to a liquid. The condensed liquid is then passed through the metering device whereat it is converted into the low pressure and low temperature vapor liquid for entry into the evaporator to complete the cycle.
An evaporating heat exchange typically comprises one or more flow passages through which refrigerant fluid travels from the inlet to the outlet of the evaporator. As the evaporator absorbs heat from the surrounding medium, refrigerant fluid within the flow passages evaporates. Ideally, an equal ratio of gas-to-liquid refrigerant will travel through each flow passage of an evaporating heat exchanger, as this yields a high heat transfer rate. A high heat transfer rate can translate into improved performance, greater efficiency, reduced power consumption, increased capacity and/or smaller package size.
In some prior art systems, the evaporator is an aluminum, parallel-flow, micro-channel heat exchanger evaporator. Micro-channel parallel-flow style heat exchangers provide enhanced heat transfer performance and efficiency over conventional round-tube, plate-fin style heat exchangers. Unfortunately, due to their construction method, micro-channel heat exchangers are not ideally suited to be evaporators in a refrigeration system. Parallel-flow micro-channel heat exchangers are constructed using two large header pipes encompassing numerous parallel, thin-section passages. Conventional round-tube, plate-fin heat exchangers do not have common header pipes, have fewer fluid flow passages, and the flow passages, are usually copper round tubing. Conventional round-tube, plate-fin heat exchangers are ideally suited for splitting up the flow passages into multiple circuits and connecting the multiple circuits to a brass refrigerant distributor from which the refrigerant flows. Refrigerant distributors are a common device used to split up the two-phase (gas and liquid) refrigerant flow from the metering/expansion device and dividing the flow into several circuits (typically 2-8), called feeder tubes, which feed directly into a multi-circuited evaporator. Distributors are designed in such a way to evenly divide the mass flow of refrigerant, providing an equal ratio of liquid and gas into each circuit. Typically, the refrigerant distributors are machined brass, and the feeder tubes are copper tubes brazed into the outlet holes of the distributors. Presently, refrigerant distributors are used with micro-channel HX evaporators by way of connecting multiple feeder tubes into various points along the header pipe. Each feeder tube supplies refrigerant to 4-6 adjacent micro-channel passages. A series of baffle, or divider, plates can be inserted into the header pipe to isolate a chamber in the header pipe where refrigerant comes from the feeder tube and splits into the 4-6 adjacent micro-channels. Making the feeder tube connection to the header pipe can be costly and troublesome due to the difficult process of joining copper and aluminum tubing, and the process of joining pure aluminum tubing together. In order to save cost, a large micro-channel HX evaporator may be divided to provide for a two-pass configuration. This saves cost by reducing the number of feeder tubes and connections to the header pipe and but the quality of refrigerant distribution is reduced. With vertical header pipe configurations of micro-channel HX evaporators, the two-phase (gas and liquid) refrigerant often separates in the header pipe due to effects of gravity or inertia of mass flow. In the case where gravity effects dominate, the liquid settles to the lower sections, and gas rises to upper sections. This causes uneven mass distribution of the refrigerant flow through the heat exchanger. The liquid floods the lower portions without completing the evaporative phase change. Also, the gas will not undergo any phase change, reducing the amount of heat absorption capacity. For cases when the mass flow inertia effects dominate, the liquid can be trapped at corners or pockets of stagnate flow. The uneven mass distribution results in poor performance and efficiency loss. Ideally, there should be an equal ratio of gas to liquid refrigerant in each micro-channel at any particular location along the channel length.

SUMMARY OF THE INVENTION

The present invention provides a means for evenly distributing refrigerant into a common header pipe of a parallel-flow, micro-channel, heat exchanger evaporator of a refrigeration system. At least one embodiment of the invention provides an evaporating heat exchanger comprising a first header pipe; a second header pipe; a header inlet chamber within the first header pipe; a header outlet chamber within the second header pipe; a multitude of channels, substantially parallel to each other and extending between the first header pipe and the second header pipe and forming flow passages from the inlet chamber and to the outlet chamber; and an inlet to the first header pipe, the inlet having a distributor nozzle; the distributor nozzle comprising: a distributor body having a first end, a second end, a longitudinal axis extending between the ends, a cylindrical inlet formed in the first end at a first diameter, and a plurality of outlets generally at the second end of the body; an orifice plate positioned within the inlet of the distributor body; the orifice plate having an orifice therethrough having a second diameter smaller than the diameter of the inlet; the distributor body having a mixing chamber between the orifice plate and the second end of the body capable of evenly mixing a two phase refrigerant; the plurality of outlets formed in the second end to provide even distribution of a two phase refrigerant to the entire length of the first header pipe.
At least one embodiment of the invention provides a heatpump system comprising an evaporating heat exchanger as set forth in the preceding paragraph, a condensing heat exchanger, a compressor, and lines connecting these components together so that refrigerant fluid can flow therethrough.
At least one embodiment of the invention provides a method of evenly distributing a two phase refrigerant to a header pipe of an evaporating heat exchanger comprising the steps of: providing a distributor nozzle comprising a distributor body having a first end, a second end, a longitudinal axis extending between the ends, a cylindrical inlet formed in the first end at a first diameter, and a plurality of outlets generally at the second end of the body; evenly mixing a two phase refrigerant by directing two phase refrigerant into an orifice plate positioned within the inlet of the distributor body and allowing the two phase refrigerant to evenly mix in a mixing chamber between the orifice plate and the second end of the body; evenly distributing the evenly mixed two phase refrigerant to the header pipe by directing the refrigerant through the plurality of outlets formed in the second end of the distributor nozzle.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this invention will now be described in further detail with reference to the accompanying drawing, in which:

FIG. 1 is a cross-sectional view of an embodiment of a parallel-flow, micro-channel heat exchanger in accordance with the present invention;

FIG. 2 is a detailed cross-sectional view of a distributor nozzle positioned in the header pipe of the parallel-flow, micro-channel heat exchanger shown in FIG. 1;

FIG. 3 is a perspective view of an orifice plate used in the distributor nozzle of FIG. 2;

FIG. 4A is a top view of the distributor nozzle of FIG. 2; FIG. 4B is an outlet end view of the distributor nozzle of FIG. 2; FIG. 4C is a cross-sectional view of the distributor nozzle of FIG. 2; and FIG. 4D is a perspective view of the distributor nozzle of FIG. 2;

FIG. 5 is a cross-sectional view of another embodiment of a parallel-flow, micro-channel heat exchanger in accordance with the present invention;

FIG. 6 is a detailed cross-sectional view of a fan style distributor nozzle attached to the header pipe of the parallel-flow, micro-channel heat exchanger shown in FIG. 5; and

FIG. 7 is an exploded perspective view of the fan style distributor nozzle and the parallel-flow, micro-channel heat exchanger shown in FIG. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention evenly distributes two-phase (liquid and gas) refrigerant over the entire length of the header pipe of a parallel-flow, micro-channel heat exchanger. Referring now to the drawings, and initially to FIG. 1, a heatpump system 10 is schematically shown. The heatpump system 10 can be used to control the temperature of a certain medium and generally comprises a heat exchanger 12, a compressor 14, a heat exchanger 16, and a metering device 18. A plurality of lines connect the components 12, 14, 16 and 18 so that refrigerant fluid can cycle therethrough. In the illustrated embodiment, line 20 connects the outlet of the heat exchanger 12 to the suction of the compressor 14, the line 22 connects the discharge of the compressor 14 to the inlet of the heat exchanger 16, the line 24 connects the outlet of the heat exchanger 16 to the inlet of the metering device 18, and the line 26 connects the outlet of the metering device 18 to the inlet of the heat exchanger 12. For the purposes of the present disclosure, the term “line” means any pipe, tube, duct or other device(s), in tandem, series, parallel or otherwise, through which fluid is circulated through the heatpump system 10.
In the illustrated embodiment, the heatpump system 10 is operates in a forward (cooling) direction whereby the system 10 is a refrigeration system and/or air-conditioning system. The heat exchanger 12 is the evaporating heat exchanger (i.e., the evaporator) and is positioned within or adjacent to the medium. The heat exchanger 16 is the condensing heat exchanger (i.e., the condenser) and is positioned remote from the medium.
Refrigerant fluid exits the evaporating heat exchanger 12 as low pressure gas, and is drawn by suction to the compressor 14 (via line 20). The compressor 14 increases the pressure and temperature of gaseous refrigerant for conveyance to the condensing heat exchanger 16 (via line 22). In the condenser 16, the refrigerant is condensed to a high pressure and low temperature liquid. En route back to the evaporator 12 (via line 24), the high pressure liquid is passed through the metering device 18 whereat its pressure is reduced. The pressure-reduced refrigerant fluid enters the evaporating heat exchanger 12 (via line 26) as low pressure and low temperature vapor-liquid. As the vapor-liquid passes through the evaporator 12, it is boiled into low pressure gas, which is drawn by the compressor 14 (via line 20) to repeat the cycle.
Referring now to FIG. 2, the evaporating heat exchanger 12 is shown isolated from the rest of the heatpump system 10. The evaporator 12 comprises a first header pipe 30, a second header pipe 32, an inlet chamber 34 within the first header pipe 30 and an outlet chamber 36 within the second header pipe 32. The first header pipe 30 is connected to the line 26, via inlet pipe 18 and the second header pipe 34 is connected, via outlet pipe 40, with the line 20 to the compressor 14. The evaporator 12 further comprises a plurality of channels 44 extending between the first header pipe 30 and the second header pipe 32 and forming flow passages from the inlet chamber 34 and to the outlet chamber 36. The suction of the compressor 14 pulls the refrigerant fluid from the inlet chamber 34, through the flow channels 44, into the outlet chamber 36 and then through the outlet pipe 40 to the compressor-intake line 20.
The header pipes 30 and 32 can be vertically oriented, as shown, with the lower end of the first header pipe 30 forming its inlet and the upper end of the second pipe 32 forming its outlet. Other orientations of the header pipes 30 and 32 are certainly possible and contemplated. However, it may be noted that in this common (and often desired) vertical orientation of the first header pipe 30, liquid has a tendency to accumulate in a lower area of the inlet chamber 34. It is also noted that the inlet chamber 34 is free of baffles or other features in the prior art required to provide a more even flow of refrigerant within the header pipe.
The channels 44 can be microchannels, that is channels having micro-sized flow areas. For example, if the channels 44 are rectangular in cross-section, they can have a width and a length between about 0.1 mm to about 40 mm, about 1 mm to about 30 mm, and/or about 1 mm to about 20 mm. One dimension can be somewhat greater than the other dimension, such as about 70% greater and/or about 80% greater. For example, the width/length can be between about 0.1 mm and about 10 mm, and the length/width can be between about 5 mm and about 40 mm. The channels 44 can have approximately the same flow areas, or their flow areas can differ in a sequential, staggered, or other manner. Likewise, the spacing between adjacent channels 44 can be the same throughout the length of the inlet chamber 34, or inter-channel spacing can be varied.
The small or micro-sized channels 44 allow the evaporator 12 to host a multitude of channels in a relatively small space, thereby significantly increasing its effective heat exchange area. The heat exchanger 12 can include, for example, more than about twenty channels 44, more than about fifty channels 44, and/or more than about a hundred channels 44. Additionally or alternatively, for example, the heat exchanger 12 can include at least one channel 44, at least two channels 44, at least five channels 44, and/or at least ten channels 44, per about 1 cm length of the first header pipe 30.
Referring to FIGS. 2-4D, a distributor nozzle 110 is shown partially inserted into the first header pipe 30 as best shown in detail in FIG. 3. The distributor nozzle 110 comprises a distributor body 50 having a first end 52, a second end 54, a longitudinal axis A extending between the ends 52, 54, a cylindrical inlet 56 formed in the first end 52 at a first diameter D1, and a plurality of outlets 58 generally at the second end 54 of the body 50. An orifice plate 60, commonly referred to as a nozzle and also shown in FIG. 4, is positioned within the inlet 56 of the distributor body 50, the orifice plate 60 having an orifice 62 therethrough having a second diameter D2 smaller than the diameter D1 of the inlet 56. The distributor body 50 also includes a mixing chamber 51 between the orifice plate 60 and the second end 54 of the body 50 capable of evenly mixing a two phase refrigerant. The plurality of outlets 58 are formed in the second end 54 to provide even distribution of a two phase refrigerant to the entire length of the first header pipe 30.
The function of the nozzle 60 is to induce turbulence of the two-phase refrigerant flow adjacently downstream of the nozzle 60. Hence, the volume space 52 in FIG. 3 directly downstream of the nozzle 60 will function as a turbulent mixing chamber, where the two-phase refrigerant (liquid and gas) are effectively blended into a homogenous mixture. The two-phase refrigerant, now uniformly mixed, is then forced through a multiple number of orifices 58, as shown in FIGS. 5A through 5D and is sprayed into the header pipe 30 of the micro-channel heat exchanger 12. The orifices 58 themselves are specially sized and strategically placed on the tip of the spray head distributor 110 to provide the optimum refrigerant mass distribution and evaporator performance. The distributor 110 may be placed at least partially into a circular opening in the side of the header pipe 30, and brazed in place at same time when the entire heat exchanger 12 is brazed together, typically through a furnace type process.
As shown in FIG. 5C the mixing chamber 51 is generally cylindrical and formed at a third diameter D3 larger than the second diameter D2 of the orifice 62 and smaller than the first diameter D1 of the inlet 56. The distributor may also include a generally cylindrical exit chamber 53 formed adjacent the mixing chamber 51, the exit chamber 53 formed at a fourth diameter D4 generally the same size as the second diameter D2 of the orifice 62.
The distributor body 50 may have a second end 54 that is frustoconical. As shown in FIGS. 2-3, the frustoconical portion of the distributor body 50 extends at least partially into the first header pipe 30. The distributor body 50 is shown attached to the first header pipe 30 generally at a midpoint of the first header pipe 30. It is also noted that at least one of the plurality of outlets 58 is parallel to the longitudinal axis of the distributor and at least two of the plurality of outlets 58 are perpendicular to the longitudinal axis A of the distributor 110. In the embodiment shown, at least two of the plurality of outlets 58 are spaced 180 degrees apart and that the majority of the plurality of outlets 58 are generally directed toward the ends of the first header pipe 30. These features help provide the even distribution of the two phase refrigerant throughout the first header pipe 30.
A second embodiment of the heat exchanger 12′ includes a “fan distributor” 110′ as shown in FIGS. 6-8. Refrigerant enters the distributor 110′ through the inlet tube 18. The fan distributor 110′ also has a restrictor orifice plate 60, or nozzle. As previously discussed, the nozzle 60 induces turbulence of the two-phase refrigerant flow adjacently downstream of the nozzle 60. Hence, the volume 51′ directly downstream of the nozzle will function as a turbulent mixing chamber, where the two-phase refrigerant (liquid and gas) are effectively blended into a homogenous mixture. The two-phase refrigerant, now uniformly mixed, is then forced through a multiple number of passages 58′ as best shown in FIG. 7. The passages 58′ enable the distributor 110′ to spray refrigerant into various locations across the header pipe 30′ of the micro-channel heat exchanger 10 as shown in FIG. 6. The passages 58′ themselves are specially sized and strategically directed to various points along the heat exchanger header pipe 30′ to provide the optimum refrigerant mass distribution and evaporator performance.
In another embodiment of the heat exchanger 12″, the fan style distributor 110″ may be made as two separate halves 72 and 74 as shown in FIG. 8, then joined together during the heat exchanger brazing process. The two separate halves 72, 74 may be economically manufactured as an aluminum die-casting or stamping process, which is lower cost than machining, or drilling the passages. Once the two halves 72, 74 are joined together, along with the nozzle 60 and inlet tube 18, the fan distributor 110″ is placed into a longitudinal slot opening in the side of the header pipe 30′. The fan distributor assembly 110″ will be brazed together and in place onto the heat exchanger 12″ at same time that the entire heat exchanger is brazed together, typically through a furnace type process.
Although the principles, embodiments and operation of the present invention have been described in detail herein, this is not to be construed as being limited to the particular illustrative forms disclosed. They will thus become apparent to those skilled in the art that various modifications of the embodiments herein can be made without departing from the spirit or scope of the invention. Accordingly, the scope and content of the present invention are to be defined only by the terms of the appended claims.

Claims

1. An evaporating heat exchanger comprising:

a first header pipe;

a second header pipe;

a header inlet chamber within the first header pipe;

a header outlet chamber within the second header pipe;

a multitude of channels, substantially parallel to each other and extending between the first header pipe and the second header pipe and forming flow passages from the inlet chamber and to the outlet chamber; and

an inlet to the first header pipe, the inlet having a distributor nozzle;

the distributor nozzle comprising:

a distributor body having a first end, a second end, a longitudinal axis extending between the ends, a cylindrical inlet formed in the first end at a first diameter, and a plurality of outlets generally at the second end of the body;

an orifice plate positioned within the inlet of the distributor body; the orifice plate having an orifice therethrough having a second diameter smaller than the diameter of the inlet;

the distributor body having a mixing chamber between the orifice plate and the second end of the body capable of evenly mixing a two phase refrigerant;

the plurality of outlets formed in the second end to provide even distribution of a two phase refrigerant to the entire length of the first header pipe.

2. The evaporating heat exchanger of claim 1, wherein the mixing chamber is generally cylindrical and formed at a third diameter larger than the second diameter of the orifice and smaller than the first diameter of the inlet.

3. The evaporating heat exchanger of claim 2 further comprising a generally cylindrical exit chamber formed adjacent the mixing chamber, the exit chamber formed at a fourth diameter generally the same size as the second diameter of the orifice.

4. The evaporating heat exchanger of claim 1, wherein an exterior of the second end of the distributor body is frustoconical.

5. The evaporating heat exchanger of claim 4, wherein the frustoconical portion of the distributor body extends into the first header pipe.

6. The evaporating heat exchanger of claim 1, wherein the distributor is attached to the first header pipe generally at a midpoint of the first header pipe;

7. The evaporating heat exchanger of claim 1, wherein at least one of the plurality of outlets is parallel to the longitudinal axis of the distributor

8. The evaporating heat exchanger of claim 1, wherein at least two of the plurality of outlets are perpendicular to the longitudinal axis of the distributor

9. The evaporating heat exchanger of claim 1, wherein the at least two of the plurality of outlets are spaced 180 degrees apart.

10. The evaporating heat exchanger of claim 1, wherein plurality of outlets are spaced 180 degrees apart.

11. The evaporating heat exchanger of claim 1, wherein the majority of the plurality of outlets are generally directed toward the ends of the first header pipe.

12. The evaporating heat exchanger of claim 1, whereih the p urality of outlets fan out from the mixing chamber and extend through the wall of the first header pipe at spaced intervals.

13. The evaporating heat exchanger of claim 1, wherein the distributor further comprises a fan portion through which the plurality of outlets fan out from the mixing chamber and extend through the wall of the first header pipe at spaced intervals.

14. The evaporating heat exchanger of claim 1, wherein the plurality of outlets fan out from the mixing chamber and extend through the wall of the first header pipe at spaced intervals.

15. The evaporating heat exchanger of claim 1, wherein the distributor is formed primarily as two symmetric, or semi-symmetric, halves, then mated together and inserted into the a slot on the side of the heat exchanger header pipe.

16. The evaporating heat exchanger of claim 14, wherein the orifice plate is inserted into the inlet of the distributor either after the halves are mated or prior to the halves being mated together.

17. The evaporating heat exchanger of claim 1, wherein the inlet chamber of the first header pipe is free of baffles.

18. A heatpump system comprising an evaporating heat exchanger as set forth in claim 1, a condensing heat exchanger, a compressor, and lines connecting these components together so that refrigerant fluid can flow therethrough.

19. A method of evenly distributing a two phase refrigerant to a header pipe of an evaporating heat exchanger comprising the steps of:

providing a distributor nozzle comprising a distributor body having a first end, a second end, a longitudinal axis extending between the ends, a cylindrical inlet formed in the first end at a first diameter, and a plurality of outlets generally at the second end of the body;

evenly mixing a two phase refrigerant by directing two phase refrigerant into an orifice plate positioned within the inlet of the distributor body and allowing the two phase refrigerant to evenly mix in a mixing chamber between the orifice plate and the second end of the body;

evenly distributing the evenly mixed two phase refrigerant to the header pipe by directing the refrigerant through the plurality of outlets formed in the second end of the distributor nozzle.

20. The method of claim 18, wherein the step of evenly distributing the refrigerant to the header pipe by directing the refrigerant through the plurality of outlets formed in the second end of the distributor nozzle is accomplished by forming the second end of the nozzle such that the majority of outlets are directed generally toward the ends of the header pipe.