EP3314191B1

EP3314191B1 - Two phase distributor evaporator

Info

Publication number: EP3314191B1
Application number: EP16739622.5A
Authority: EP
Inventors: Abbas A. Alahyari; Richard Rusich; Thomas D. Radcliff
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2015-06-29
Filing date: 2016-06-28
Publication date: 2020-09-30
Anticipated expiration: 2036-06-28
Also published as: ES2822826T3; US20180156544A1; EP3314191A1; CN107850396A; WO2017004058A1

Description

BACKGROUND

This disclosure relates generally to heat exchangers and, more particularly, to a heat exchanger distributor assembly and a method of distributing fluid to a heat exchanger.
Uniform distribution of two-phase fluid flow (liquid and gas) inside heat exchangers is difficult to achieve. In heat exchangers, such as mini-channel, microchannel, plate-fin, and brazed-plate heat exchangers for example, distribution is particularly difficult due to the requirement that the flow be distributed among many layers and small ports. To overcome these challenges, these types of heat exchangers may employ a distributor having a closed-end tube with a series of holes in the side. However, such distributors may not prevent separation of the two-phase fluid under different operating conditions.
WO 2006/043864 discloses a plate heat exchanger for two phase refrigerant having the features in the preamble of claim 1. DE 199 45 978 A1 discloses a plate heat exchanger.

SUMMARY

According to an aspect of the invention, a heat exchanger is provided. The heat exchanger is for two-phase refrigerant and includes a plurality of parallel stacked plates defining at least one flow passage there between. A manifold having a generally hollow interior is arranged adjacent the plurality of parallel plates. An opening is disposed between adjacent stacked plates. The opening is configured to fluidly couple the hollow interior of the manifold and the at least one flow passage. A distributor assembly including an insert is disposed at least partially within the hollow interior of the manifold. The insert includes distribution flow paths comprising a plurality of circumferentially spaced axial flow channels and a plurality of radial connecting channels arranged in fluid communication with the axial flow channels. The radial flow channels are fluidly coupled to the at least one flow passage via the opening. The distribution flow paths are sized to maintain the velocity of the two-phase fluid so as to limit separation.
A portion of the manifold may be received within at least one of the plurality of plates.
The entire manifold may be received within the plurality of plates.
An edge of the manifold may be arranged in contact with an outer edge of the plurality of plates.
There may be a plurality of axially spaced circumferential connecting channels fluidly coupling the radial connecting channels to the at least one flow passage via the opening.
Each of the at least one flow passages may be arranged in fluid communication with the hollow interior of the manifold via exactly one opening.
The opening may be defined by at least one of a ridge extending from at least one of the plurality of stacked plates defining the flow passage and a seal surrounding a portion of the manifold adjacent the flow passage fluidly coupled thereto.
A seal may completely surrounding the manifold adjacent the flow passage fluidly coupled thereto. The seal may comprise an aperture defining the opening.
A fluid within the distributor assembly may be supplied to the plurality of axial flow channels substantially equally.
The distributor assembly may be configured to supply a fluid to each opening at a substantially identical azimuthal angle.
The distributor assembly may be configured to supply a fluid to each opening at a different azimuthal angle.
The distributor assembly may further comprise a nozzle arranged upstream from the plurality of axial flow channels, the nozzle being configured to create a homogeneous distribution of a fluid.
The nozzle may include a constriction configured to produce a pressure drop in the fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the present disclosure, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is an example of a conventional vapor compression system;
FIG. 2 is a exploded view of an example of a parallel flow brazed plate heat exchanger;
FIGS. 2a-2c are cross-sectional views of various manifold configurations;
FIG. 3 is a cross-sectional view of a portion of the parallel flow heat exchanger of FIG. 2;
FIG. 4 is a perspective view of a distributor configured for use in a manifold of a heat exchanger according to an embodiment of the present disclosure;
FIG. 5 is a cross-sectional view of the distributor of FIG. 4 according to an embodiment of the present disclosure; and
FIG. 6 is a front view of a plate of a plate-fin heat exchanger and an adjacent distribution channel fluidly coupled thereto according to another embodiment of the present disclosure.

The detailed description explains embodiments of the present disclosure, together with advantages and features, by way of example with reference to the drawings.

DETAILED DESCRIPTION

Obstacles exist to the use of microchannel heat exchangers within a refrigerant system. In particular, refrigerant flow maldistribution may occur in the heat exchanger when a homogeneous two-phase mixture is allowed to phase separate in the manifold. For example, a vapor phase of the two-phase mixture has significantly different properties and is subjected to different effects of internal forces than a liquid phase. This can contribute to phase separation if the velocity of the homogeneous two-phase mixture is reduced (e.g., as the flow area expands entering the manifold). As a result, the flow may stratify due to deceleration in the manifold such that the flow to each passage of the heat exchanger may not be properly apportioned.
An example of a basic refrigerant system 20 is illustrated in FIG. 1 and includes a compressor 22, condenser 24, expansion device 26, and evaporator 28. The compressor 22 compresses a fluid, such as refrigerant for example, and delivers it downstream into a condenser 24. From the condenser 24, the refrigerant passes through the expansion device 26 into an inlet refrigerant pipe 30 leading to the evaporator 28. From the evaporator 28, the refrigerant is returned to the compressor 22 to complete the closed-loop refrigerant circuit.
Referring now to FIG. 2, an example of a heat exchanger 40, for example configured for use as the evaporator 28 of the system 20, is illustrated in more detail. Although described with respect to vapor compression system 20, the heat exchanger 40 of the present disclosure may be configured for use in a plurality of other processes, such as pumped refrigerant loops, Rankin cycles, or other industrial heat exchange applications. In the illustrated, non-limiting embodiment, the heat exchanger 40 is a brazed plate heat exchanger; however, other types of heat exchangers, such as microchannel heat exchangers and plate fin heat exchangers for example, are within the scope of the present disclosure.
As depicted, the heat exchanger 40 comprises a plurality of corrugated plates 42a, 42b disposed along substantially parallel plates and being stacked in an alternating arrangement. The plates 42a, 42b may be made of stainless steel, sheet metal clad, or are otherwise coated with a thin layer of braze material (not shown) that provides a joining interface at contact points between adjacent plates 42a, 42b. For assembly, plates 42a, 42b are temporarily clamped together and heated to permanently braze plates 42a, 42b together to create alternating layers of a plurality of primary passages 44 and a plurality of secondary passages 46 between adjacent plates 42a, 42b. The brazing operation hermetically seals an outer peripheral edge of the plates 42a, 42b.
The actual design of the plates 42a, 42b may vary to provide an infinite number of configurations with any number of passes and flow patterns, such as including ridges for example. The patterns may be formed such as by stamping, etching, engraving, extruding, molding and embossing for example. As illustrated in FIG. 2, the heat exchanger 40 is shown having a first fluid inlet manifold 48, a first fluid outlet manifold 50, a second fluid inlet manifold 52, and a second fluid outlet manifold 54. Each plate 42a, 42b includes a first fluid supply opening 48a, 48b, a first fluid return opening 50a, 50b a second fluid supply opening 52a, 52b and a second fluid return opening 54a, 54b, respectively. A seal (not shown) may surround a portion of the manifold 48, 50, 52, and 54 adjacent a flow passage to form the openings 48a, 48b, 50a, 50b, 52a, 52b, 54a, 54b.
Although the plurality of manifolds 48, 50, 52, and 54 illustrated in FIG. 2 are shown as being substantially encased by a portion of the plates 42a, 42b, other configurations where only a portion of one or more of the manifolds 48, 50, 52, and 54 is received within plates 42a, 42b (FIG. 2a) or where the manifolds 48, 50, 52, and 54 are separate from but arranged in a fluid communication with an edge of the plates 42a, 42b are within the scope of the disclosure FIG. 2b). In one embodiment, a portion of one of the manifolds 48, 50, 52, and 54 may be arranged in contact with an inner edge of one of the plurality of plates 42, and arranged in contact with an outer edge of another of the plurality of plates 42. In the illustrated, non-limiting embodiment, the manifolds 48, 50, 52, and 54, comprise longitudinally elongated, generally hollow, closed end cylinders having a circular cross-section. However, manifolds having other configurations, such as a semi-circular, semi-elliptical, square, rectangular, or other cross-section for example, are within the scope of the present disclosure. The manifolds can extend from opposite end plates of the heat exchanger 40.
When the heat exchanger 40 is used as an evaporator in an HVAC system, such as system 20 for example, a relatively cool refrigerant enters the heat exchanger 40 through the first fluid supply openings 48a, 48b. Openings 48a, deliver the refrigerant to passages 44, which convey refrigerant in a zig-zag or other configuration between adjacent plates 42a, 42b to refrigerant return openings 50a, 50b. Openings 50a and 50b then direct the refrigerant to outlet manifold 50 to recycle the refrigerant through the system. Similarly, a second fluid to be cooled enters the heat exchanger 40 through inlet manifold 52 and flows through the openings 52a, 52b. Openings 52b of the heat exchanger 40 deliver the second fluid to passages 46, which convey the second fluid in a zig-zag or other configuration between adjacent plates 42a, 42b to the second fluid return openings 54a, 54b. As the second fluid flows through passages 46, the refrigerant in the adjacent passages 44 cools the second fluid. After the second fluid is cooled, openings 54a, 54b direct the chilled second fluid to the second fluid outlet manifold 54, where it is then provided to an environment to be conditioned.
Referring now to FIGS. 3- 6 a longitudinally elongated distributor assembly 70 configured for use within the interior volume of an inlet manifold, such as refrigerant inlet manifold 48 of heat exchanger 40, is illustrated. Although illustrated within a horizontally arranged manifold 48, the distributor assembly 70 may also be used in any or non-horizontal orientation (e.g., a vertical orientation). The distributor assembly 70 extends over at least a portion, if not the entire length of the inlet manifold 52. In addition, the distributor assembly 70 may be centered within the manifold 48, or alternatively, may be off-center, such as skewed towards a wall of the manifold 48 opposite the plates 42a, 42b for example.
The distributor assembly 70 includes an insert 72 having a cross-sectional shape including, but not limited to, round, elliptical, and rectangular for example. In one embodiment, the size and shape of the insert 72 is generally complementary to the manifold 48. The insert 72 has a plurality of distribution flow paths 74 formed therein such that the refrigerant provided at an inlet of the manifold 52, such as from line 30 of the vapor refrigerant circuit 20 for example, is distributed substantially equally between the flow paths 74. The refrigerant flow paths 74 extend from an internal cavity of the distributor insert 72 to the flow passage 44 formed between adjacent heat exchanger plates 42a, 42b. The distribution flow paths 74 are sized to maintain the velocity of the two-phase mixture (e.g., so as to limit phase separation) and may be any shape such as round, rectangular, oval, or any other shape for example. In addition, the distribution flow paths 74 may take any path, such as a helical path, or a linear path with a metered bend for example.
By separating a two-phase mixture with a known liquid-vapor distribution (e.g., a homogeneous distribution, where no significant portions of the flow volume contain only one phase) into the plurality of distribution flow paths 74, the likelihood that the distribution of the two-phase mixture settles or redistributes (except within each flow paths 74) can be reduced. In addition, if each of the plurality of distribution flow paths 74 is formed having an appropriately small diameter, for example between about 0.2 mm and 5 mm, redistribution of the phases of the flow is unlikely to occur because the slip between the velocity of the liquid portion and the vapor portion of the refrigerant is minimized. In an embodiment, the plurality of distribution flow paths 74 have equal diameters (excepting for normal manufacturing variation in dies or other manufacturing tools due to imprecision in the tool construction or wear). In another embodiment, the diameter of each flow paths 74 is selected to reduce the variation in flow resistance between different flow circuits of the heat exchanger (to nearly match pressure drop characteristics of each flow path between the manifold inlet to the manifold outlet of the heat exchanger).
In the illustrated, non-limiting embodiment, each of the plurality of distribution flow paths 74 includes a first portion or flow channel 76 extending axially over at least a portion of the length of the insert 72. The axial flow channels 76 may be parallel to and circumferentially spaced about a central axis of the insert 72, such as in an equidistantly spaced configuration for example. As shown in FIG. 3, the plurality of axial flow channels 76 may vary in length to provide a fluid flow to one or more corresponding passages 44 via refrigerant supply openings 48a, 48b. Variation in the lengths of the axial flow channels 76 may additionally be used to equalize the pressure drop of the fluid, and therefore the flow between the plurality of axial flow channels 76. Alternatively, the plurality of axial flow passages 76 may be substantially identical in length, such as extending over the full length of the insert 72, as shown in FIG. 5 for example.
The distribution flow paths 74 additionally include a plurality of axially spaced connecting channels 78, each of which is configured to fluidly couple at least one of the axial flow channels 76 to a refrigerant supply opening 48a, 48b and one or more of the passages 44 formed between adjacent plates 42a, 42b. Accordingly, at least one connecting channel 78 is arranged in fluid communication with each of the plurality of axial flow channels 76. As shown in FIG. 3, each of the plurality of connecting channels 78 extends radially outward from an axial flow channel 76 to a distribution hole 80 formed in an outer surface 82 of the insert 72. In such embodiments, the connecting channels 78 are at least partially integrally formed with the insert 72.
One or more of the plurality of connecting channels 78 may additionally extend at least partially around a circumference of the insert 72. In one embodiment, the circumferential portion of the plurality of connecting channels 78 may be integrally formed as a portion of the heat exchanger plates 42a, 42b (FIG. 6). In another embodiment, the circumferential portion of the plurality of connecting channels 78 may be formed in one or both of the exterior surface 82 of the insert 72 and an inner surface 49 of the manifold 48. The distributor assembly 70 may additionally include an outer sleeve 84, as shown in FIGS. 4 and 5, arranged in an overlapping configuration with the insert 72 and being configured to define a portion of the connecting channels 78 to retain fluid therein. A distributor assembly 70 having circumferentially extending connecting channels 78 and an outer sleeve 84 is described in more detail in U.S. Patent Publication No. US2014/0345837, filed on May 23, 2013 , the entire contents of which are incorporated herein by reference.
As shown, a plurality of distribution holes 80 may be formed in either the outer surface 82 of the insert 72 or in an outer sleeve 84 positioned about the insert 72 and are fluidly connected to not only the distribution flow paths 74 but also the openings 48a, 48b connected to passages 44. In another configuration, the plurality of distribution holes 80 may be replaced by one or more continuous slots. In embodiments having a plurality of distinct distribution holes 80, each distribution hole 80 may be connected to one or more corresponding connecting channels 78. Alternatively, a plurality of distribution holes 80 may be configured to receive a fluid flow from a single connecting channel 78.
In the illustrated, non-limiting embodiment of FIG. 4, the distribution holes 80 are arranged along a horizontal axis such that the position of each hole 80 about the circumference of the housing distributor assembly 70 is substantially identical. As a result, the refrigerant flow is delivered to each of the refrigerant supply openings 48a, 48b at the same azimuthal angle. In another embodiment (FIG. 3), the distribution holes 80 are positioned at different circumferential angles relative to one another.
Referring again to FIGS. 4 and 5, the distributor 70 may also include a nozzle or orifice 90 arranged generally upstream from the plurality of axial flow channels 76. The nozzle 90 may be a separate component positioned adjacent an end of the insert 72, or alternatively, may be located within a hollow region of the insert 72. In such embodiments, the nozzle 90 is fluidly coupled to line 30 of the vapor refrigerant circuit 20 (FIG. 1) such that substantially all of the refrigerant from the expansion device 26 is configured to flow directly into the insert 72 via the nozzle 90. The nozzle 90 includes an orifice that restricts the cross-sectional area of the fluid inlet path and is configured to increase the velocity of the fluid flowing there through. Increasing the velocity 14 advantageously provides a substantially uniform, homogeneous mixture of fluid 14. In one embodiment, the orifice of the nozzle 90 comprises a venturi portion to reduce the pressure drop of the fluid passing there through. The homogenous two-phase refrigerant mixture may be output from the nozzle 90 in a generally conical shape and is supplied to the plurality of distribution flow paths 74 formed in the insert 72 (see FIG. 5).
The distributor assembly 70 as disclosed herein is configured to provide more uniform distribution to a plurality of flow passages of a heat exchanger 40, particularly a heat exchanger configured as an evaporator, and even more particularly a brazed plate heat exchanger. This homogenized distribution will result in improved performance over a wider range of flow conditions. As a result, a refrigerant system 20 including the heat exchanger 40 will have an increased coefficient of performance and reduced power consumption.
While the present disclosure has been particularly shown and described with reference to the exemplary embodiments as illustrated in the drawing, it will be recognized by those skilled in the art that various modifications may be made without departing from the scope of the present invention as defined by the claims. Therefore, it is intended that the present disclosure not be limited to the particular embodiment(s) disclosed as, but that the disclosure will include all embodiments falling within the scope of the appended claims.

Claims

A heat exchanger, for two-phase refrigerant, the heat exchanger comprising:
a plurality of parallel stacked plates (42a,42b) defining at least one flow passage (44,46) there between;

a manifold (48,50,52,54) arranged adjacent the plurality of parallel plates, the manifold having a generally hollow interior;

an opening (48a,48b,50a,50b,52a,52b,54a,54b) disposed between adjacent stacked plates, the opening being configured to fluidly couple the hollow interior of the manifold and the at least one flow passage; and

a distributor assembly (70) including an insert (72) disposed at least partially within the hollow interior of the manifold; characterised in that the insert including distribution flow paths (74) comprising a plurality of circumferentially spaced axial flow channels (76) and a plurality of radial connecting channels (78) arranged in fluid communication with the axial flow channels, the radial flow channels being fluidly coupled to the at least one flow passage via the opening; wherein the distribution flow paths are sized to maintain the velocity of the two-phase refrigerant so as to limit separation
The heat exchanger according to claim 1, wherein a portion of the manifold (48,50,52,54) is received within at least one of the plurality of plates (42a,42b).
The heat exchanger according to either claim 1 or claim 2, wherein the entire manifold (48,50,52,54) is received within the plurality of plates (42a,42b).
The heat exchanger according to either claim 1 or claim 2, wherein an edge of the manifold (48,50,52,54) is arranged in contact with an outer edge of the plurality of plates (42a,42b).
The heat exchanger according to any of the preceding claims, further comprising a plurality of axially spaced circumferential connecting channels (78) fluidly coupling the radial connecting channels (78) to the at least one flow passage (42a,42b) via the opening (48a,48b,50a,50b,52a,52b,54a,54b).
The heat exchanger according to any of the preceding claims, wherein each of the at least one flow passages (44,46) is arranged in fluid communication with the hollow interior of the manifold (48,50,52,54) via exactly one opening (48a,48b,50a,50b,52a, 52b,54a,54b).
The heat exchanger according to any of the preceding claims, wherein the opening (48a,48b,50a,50b,52a,52b,54a,54b) is defined by at least one of a ridge extending from at least one of the plurality of stacked plates (42a,42b) defining the flow passage (44,46) and a seal surrounding a portion of the manifold (48,50,52,54) adjacent the flow passage fluidly coupled thereto.
The heat exchanger of any of claims 1-6, comprising a seal completely surrounding the manifold (48,50,52,54) adjacent the flow passage (44,46) fluidly coupled thereto, and wherein the seal comprises an aperture defining the opening (48a,48b,50a,50b, 52a,52b,54a,54b).
The heat exchanger according to any of the preceding claims, wherein a fluid within the distributor assembly (70) is supplied to the plurality of axial flow channels (76) substantially equally.
The heat exchanger according to any of the preceding claims, wherein the distributor assembly (70) is configured to supply a fluid to each opening (48a,48b,50a, 50b,52a,52b,54a,54b) at a substantially identical azimuthal angle.
The heat exchanger according to any of the preceding claims, wherein the distributor assembly (70) is configured to supply a fluid to each opening (48a,48b,50a,50b, 52a,52b,54a,54b) at a different azimuthal angle.
The heat exchanger according to any of the preceding claims, wherein the distributor assembly (70) further comprises a nozzle (90) arranged upstream from the plurality of axial flow channels (76), the nozzle being configured to create a homogeneous distribution of a fluid.
The heat exchanger according to claim 12, wherein the nozzle (90) includes a constriction configured to produce a pressure drop in the fluid.