U.S. patent application number 11/794774 was filed with the patent office on 2008-05-08 for liquid-vapor separator for a minichannel heat exchanger.
This patent application is currently assigned to Carrier Corporation. Invention is credited to Mikhail B. Gorbounov, Michael K. Sahm, Parmesh Verma.
Application Number | 20080104975 11/794774 |
Document ID | / |
Family ID | 36777705 |
Filed Date | 2008-05-08 |
United States Patent
Application |
20080104975 |
Kind Code |
A1 |
Gorbounov; Mikhail B. ; et
al. |
May 8, 2008 |
Liquid-Vapor Separator For A Minichannel Heat Exchanger
Abstract
A method and apparatus for promoting uniform refrigerant flow in
a minichannel heat exchanger by providing a liquid-vapor separator
between an expansion device and the inlet header such that the
refrigerant vapor will pass directly to the compressor and only the
liquid refrigerant will pass to the inlet header. The liquid-vapor
separation is accomplished by way of a float valve which prevents
the flow of liquid refrigerant to the compressor and the flow of
refrigerant vapor from the outlet manifold, through the valve and
back to the inlet manifold. A second float valve may be provided
between a downstream end of the inlet manifold and the compressor
for the purpose of removing any residual vapor from the liquid.
Inventors: |
Gorbounov; Mikhail B.;
(South Windsor, CT) ; Sahm; Michael K.; (Avon,
CT) ; Verma; Parmesh; (Manchester, CT) |
Correspondence
Address: |
MARJAMA MULDOON BLASIAK & SULLIVAN LLP
250 SOUTH CLINTON STREET, SUITE 300
SYRACUSE
NY
13202
US
|
Assignee: |
Carrier Corporation
Farmington
CT
|
Family ID: |
36777705 |
Appl. No.: |
11/794774 |
Filed: |
December 28, 2005 |
PCT Filed: |
December 28, 2005 |
PCT NO: |
PCT/US05/47359 |
371 Date: |
July 5, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60649435 |
Feb 2, 2005 |
|
|
|
Current U.S.
Class: |
62/117 ;
62/512 |
Current CPC
Class: |
F25B 41/20 20210101;
F25B 43/006 20130101; F25B 41/22 20210101; F25B 2400/0409 20130101;
F25B 2400/23 20130101; F25B 2600/2501 20130101 |
Class at
Publication: |
62/117 ;
62/512 |
International
Class: |
F25B 43/00 20060101
F25B043/00 |
Claims
1. A liquid-vapor separator for a heat exchanger of the type having
inlet and outlet manifolds fluidly interconnected by a plurality of
parallel minichannels for conducting the flow of refrigerant
therebetween, comprising: an inlet chamber fluidly connected
between said inlet manifold and an expansion device that is adapted
to deliver two phase refrigerant thereto; a bypass duct fluidly
interconnected between said inlet chamber and a compressor inlet;
and a float valve disposed within said bypass duct and operable to
permit the flow of refrigerant vapor to said compressor but not to
permit the flow of liquid refrigerant thereto.
2. A liquid-vapor separator as set forth in claim 1 wherein said
inlet chamber is connected to the expansion device by an inlet line
and further wherein said inlet line is connected to said inlet
chamber at an upper portion thereof.
3. A liquid-vapor separator as set forth in claim 2 wherein said
inlet chamber is so constructed as to permit the flow of liquid
refrigerant to said inlet manifold but the presence of liquid
refrigerant in said inlet chamber prevents the flow of refrigerant
vapor to said inlet manifold.
4. (canceled)
5. A liquid-vapor separator as set forth in claim 1 wherein said
float valve includes an outlet port and float member moveable
upwardly to seat against and seal said outlet port.
6. A liquid-vapor separator as set forth in claim 5 wherein said
valve further includes an inlet port against which the float member
can seat as it moves downwardly to prevent the flow of refrigerant
vapor downwardly therethrough.
7. A liquid-vapor separator as set forth in claim 1 wherein said
outlet manifold is fluidly connected to the compressor.
8. A liquid-vapor separator as set forth in claim 1 and including a
conduit fluidly interconnecting a downstream end of said inlet
manifold to said compressor and said float valve is disposed within
said conduit for removal of any residual vapor from a liquid.
9. A liquid-vapor separator as set forth in claim 8 wherein said
float valve and an outlet port and a float member that is upwardly
moveable to seat thereagainst.
10. A liquid-vapor separator as set forth in claim 9 wherein said
float valve includes an inlet port against which the float member
can seat.
11. A method of promoting uniform refrigerant flow from an inlet
manifold of a heat exchanger to a plurality of parallel
minichannels fluidly connected thereto, comprising the steps of:
providing an inlet chamber for fluidly interconnecting the inlet
manifold to an expansion device adapted to deliver two phase
refrigerant thereto; providing a bypass duct for fluidly
interconnecting said inlet chamber and a compressor inlet; and
providing a float valve within said bypass duct so as to permit the
flow of refrigerant vapor to said compressor but not permit the
flow of liquid refrigerant thereto.
12. A method as set forth in claim 11 including the steps of
connecting the expansion device to an upper portion of said inlet
chamber by way of an inlet line.
13. (canceled)
14. A method as set forth in claim 11 wherein said float valve
includes an outlet port and float member moveable upwardly to seat
against and seal said outlet port.
15. A method as set forth in claim 14 wherein said float valve
further includes an inlet port against which the float member can
seat as it moves downwardly to prevent the flow of refrigerant
vapor downwardly therethrough.
16. A method as set forth in claim 15 and including the further
step of fluidly connecting said outlet manifold to the
compressor.
17. A method as set forth in claim 11 and including the further
step of fluidly interconnecting a downstream end of said inlet
manifold to said compressor by way of a conduit.
18. A method as set forth in claim 17 and including the further
step of providing said float valve within said conduit for removal
of any residual vapor from a liquid.
19. A method as set forth in claim 18 wherein said float valve
includes an outlet port and a float member that is upwardly
moveable to seat thereagainst.
20. A method as set forth in claim 19 wherein said float valve
includes an inlet port against which the float member can seat.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates generally to air conditioning and
refrigeration systems and, more particularly, to parallel flow
evaporators thereof.
[0002] A definition of a so-called parallel flow heat exchanger is
widely used in the air conditioning and refrigeration industry now
and designates a heat exchanger with a plurality of parallel
passages, among which refrigerant is distributed and flown in the
orientation generally substantially perpendicular to the
refrigerant flow direction in the inlet and outlet manifolds. This
definition is well adapted within the technical community and will
be used throughout the text.
[0003] Refrigerant maldistribution in refrigerant system
evaporators is a well-known phenomenon. It causes significant
evaporator and overall system performance degradation over a wide
range of operating conditions. Maldistribution of refrigerant may
occur due to differences in flow impedances within evaporator
channels, non-uniform airflow distribution over external heat
transfer surfaces, improper heat exchanger orientation or poor
manifold and distribution system design. Maldistribution is
particularly pronounced in parallel flow evaporators due to their
specific design with respect to refrigerant routing to each
refrigerant circuit. Attempts to eliminate or reduce the effects of
this phenomenon on the performance of parallel flow evaporators
have been made with little or no success. The primary reasons for
such failures have generally been related to complexity and
inefficiency of the proposed technique or prohibitively high cost
of the solution.
[0004] In recent years, parallel flow heat exchangers, and brazed
aluminum heat exchangers in particular, have received much
attention and interest, not just in the automotive field but also
in the heating, ventilation, air conditioning and refrigeration
(HVAC&R) industry. The primary reasons for the employment of
the parallel flow technology are related to its superior
performance, high degree of compactness and enhanced resistance to
corrosion. Parallel flow heat exchangers are now utilized in both
condenser and evaporator applications for multiple products and
system designs and configurations. The evaporator applications,
although promising greater benefits and rewards, are more
challenging and problematic. Refrigerant maldistribution is one of
the primary concerns and obstacles for the implementation of this
technology in the evaporator applications.
[0005] As known, refrigerant maldistribution in parallel flow heat
exchangers occurs because of unequal pressure drop inside the
channels and in the inlet and outlet manifolds, as well as poor
manifold and distribution system design. In the manifolds, the
difference in length of refrigerant paths, phase separation and
gravity are the primary factors responsible for maldistribution.
Inside the heat exchanger channels, variations in the heat transfer
rate, airflow distribution, manufacturing tolerances, and gravity
are the dominant factors. Furthermore, the recent trend of the heat
exchanger performance enhancement promoted miniaturization of its
channels (so-called minichannels and microchannels), which in turn
negatively impacted refrigerant distribution. Since it is extremely
difficult to control all these factors, many of the previous
attempts to manage refrigerant distribution, especially in parallel
flow evaporators, have failed.
[0006] In the refrigerant systems utilizing parallel flow heat
exchangers, the inlet and outlet manifolds or headers (these terms
will be used interchangeably throughout the text) usually have a
conventional cylindrical shape. When the two-phase flow enters the
header, the vapor phase is usually separated from the liquid phase.
Since both phases flow independently, refrigerant maldistribution
tends to occur.
[0007] If the two-phase flow enters the inlet manifold at a
relatively high velocity, the liquid phase (droplets of liquid) is
carried by the momentum of the flow further away from the manifold
entrance to the remote portion of the header. Hence, the channels
closest to the manifold entrance receive predominantly the vapor
phase and the channels remote from the manifold entrance receive
mostly the liquid phase. If, on the other hand, the velocity of the
two-phase flow entering the manifold is low, there is not enough
momentum to carry the liquid phase along the header. As a result,
the liquid phase enters the channels closest to the inlet and the
vapor phase proceeds to the most remote ones. Also, the liquid and
vapor phases in the inlet manifold can be separated by the gravity
forces, causing similar maldistribution consequences. In either
case, maldistribution phenomenon quickly surfaces and manifests
itself in evaporator and overall system performance
degradation.
[0008] In tube-and-fin type heat exchangers, it has been common
practice to provide individual capillary tubes or other expansion
devices leading to the respective tubes in order to get relatively
uniform expansion of a refrigerant into the bank of tubes. Another
approach has been to provide individual expansion devices such as
so-called "dixie" cups at the entrance opening to the respective
tubes, for the same purpose. Neither of these approaches are
practical in minichannel or microchannel applications, wherein the
channels are relatively small and closely spaced such that the
individual restrictive devices could not, as a practical manner, be
installed within the respective channels during the manufacturing
process.
[0009] In the air conditioning and refrigeration industry, the
terms "parallel flow" and "minichannel" (or "microchannel") are
often used interchangeably in reference to the abovementioned heat
exchangers, and we will follow similar practice. Furthermore,
minichannel and microchannel heat exchangers differ only by a
channel size (or so-called hydraulic diameter) and can equally
benefit from the teachings of the invention. We will refer to the
entire class of these heat exchangers (minichannel and
microchannel) as minichannel heat exchangers throughout the text
and claims.
SUMMARY OF THE INVENTION
[0010] Briefly, in accordance with one aspect of the invention, a
liquid-vapor separator is provided between the expansion device and
the inlet header such that the separator causes the refrigerant
vapor to pass directly to the compressor and only liquid
refrigerant to pass to the inlet manifold. In this way, a more
uniform distribution of liquid refrigerant to the individual
parallel channels is obtained.
[0011] In accordance with another aspect of the invention, the
liquid-vapor separator comprises a float valve with a float member
oriented to move vertically to permit the flow of refrigerant vapor
therearound but if liquid refrigerant flows into the valve, the
float member will tend to seat and prevent the flow of liquid
refrigerant therethrough.
[0012] By yet another aspect of the invention, a second float valve
is interconnected between a downstream end of the inlet manifold
and the compressor such that the residual vapor from the liquid
refrigerant will pass directly to the compressor.
[0013] In the drawings as hereinafter described, a preferred
embodiment is depicted; however, various other modifications and
alternate constructions can be made thereto without departing from
the true spirit and scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic illustration of one embodiment of the
invention.
[0015] FIG. 2 is a modified version thereof.
[0016] FIG. 3 is an alternate embodiment of the present
invention.
[0017] FIG. 4 is a modified version thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0018] Referring now to FIG. 1, the invention is shown generally at
10 as applied to a minichannel heat exchanger 11 having an inlet
manifold 12, an outlet manifold 13, and a plurality of parallel
microchannels 14 interconnecting the inlet manifold 12 to the
outlet manifold 13.
[0019] An inlet chamber 16 is fluidly connected to the upstream end
17 of the inlet manifold 12 by way of conduit 18. At an upper
portion of the inlet chamber 16 an inlet line 19 provides fluid
communication from an expansion device such that a mixture of
liquid and vapor refrigerant flows into the upper portion of the
inlet chamber 16. The heavier liquid refrigerant tends to fall to
the bottom of the inlet chamber 16 and flow through the conduit 18
to the inlet manifold 12 such that each of the parallel
minichannels 14 have single phase liquid refrigerant presented at
their inlet ends.
[0020] Also connected at the upper portion of the inlet chambers 16
is a bypass duct 21 for conducting the flow of refrigerant vapor to
the compressor as indicated by the arrows. Disposed within the
bypass duct 21 is a float valve 22 having an inlet port 23, an
outlet port 24, and a float member 26.
[0021] In operation, as the two phase refrigerant enters the inlet
line 19, the liquid refrigerant tends to drop into the lower
portion of the inlet chamber 16 and the refrigerant vapor is drawn
upwardly by the suction of the compressor. As it enters the float
valve 22, it passes around the float member 26 and through the
outlet port 24 to the compressor. If liquid refrigerant enters the
float valve 22, it will tend to lift the float member 26 such that
it will engage the outlet port 24 and seat so as to prevent the
flow of liquid toward the compressor. The liquid refrigerant will
then drop to the lower portion of the float valve and then flow
into the inlet chamber 16.
[0022] The outlet manifold 13 is fluidly attached to the compressor
by way of an outlet line 15 so that, after the liquid refrigerant
is converted to vapor as it passes through the microchannels 14 and
into the outlet manifold 13, the refrigerant vapor is then drawn
into the compressor. It should be mentioned that, if the vapor from
the outlet line 15 tends to flow into the bypass duct 21, the float
member 26 will be caused to seat against the inlet port 23 and
prevent vapor from entering the inlet chamber 16.
[0023] Referring now to FIG. 2, a similar arrangement is shown, but
with additional features. At the downstream end 27 of the inlet
manifold 12 a conduit 28 is connected to provide fluid
communication to the compressor by way of a second float valve 29.
This float valve separator operates in the same manner as the float
valve 22 as described hereinabove to remove any residual vapor that
may be in the downstream end 27 of the inlet manifold 12. That is,
all liquid refrigerant in the manifold 12 should flow upwardly
through the microchannels 14, and any residual vapor would pass
upwardly through the conduit 28, the float valve 29 and to the
compressor.
[0024] It will also be seen in the FIG. 2 embodiment, that the
inlet chamber 16 of the FIG. 1 embodiment has been changed from its
reservoir form to a simple piping arrangement 31. While the piping
arrangement 31 will contain less liquid refrigerant, it operates in
substantially the same way as the inlet chamber 16 as described
hereinabove.
[0025] The FIG. 1 and FIG. 2 embodiments as described hereinabove
relate to arrangements wherein the heat exchanger 11 is orientated
such that the manifolds 12 and 13 are horizontal and the
minichannels 14 are vertical. The FIG. 3 embodiment illustrates the
invention as used in a configuration wherein the headers are
orientated vertically and the minichannels are orientated
horizontally.
[0026] Here the minichannel heat exchanger 32 has a manifold 33, a
manifold 34 and parallel minichannels 36. The manifold 33 is
divided into upper and lower sections 37 and 38, with the
microchannels 36 in the lower sections 38 acting to conduct the
flow of refrigerant to the manifold 34 and the minichannels in the
upper section 37 acting to conduct the flow of refrigerant from the
manifold 34 back to the upper section 37 of the manifold 33. Again,
a float valve 39 is provided in a line 41 connecting the upper
section 37 of the inlet manifold 33 to the compressor. This float
valve operates in the same manner as the float valve 29 of the FIG.
2 embodiment to remove any residual vapor from the liquid.
[0027] In the FIG. 4 embodiment, there is provided a conduit 42 for
fluid communication between the downstream end of manifold 34 and
the compressor suction. A float valve 43 is provided and operates
in the same manner as the float valve described hereinabove. Its
purpose is to separate any vapor that appears after the first pass
of the heat exchanger so that only liquid refrigerant is fed to the
second pass of the heat exchanger.
[0028] In each of the liquid-vapor separators described
hereinabove, the selection of the float member and the seats are
made to be consistent with the refrigerant fluid in respect to
density, buoyancy and seating force requirements, as well as for
material compatibility considerations.
* * * * *