Note: Descriptions are shown in the official language in which they were submitted.
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HEAT EXCHANGER WITH FLUID EXPANSION IN HEADER
Cross-Reference to Related Application
[0001] Reference is made to and this application claims priority from and the
benefit of U.S. Provisional Application Serial No. 60/649,269, filed February
2,
2005, and entitled MINI-CHANNEL HEAT EXCHANGER WITH EXPANSION
CONNECTOR, which application is incorporated herein in its entirety by
reference.
Field of the Invention
[0002] This 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 Invention
[0003] Refrigerant 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.
[0004] 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
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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.
[0005] 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.
[0006] Historically, parallel tube heat exchangers used in such refrigerant
compression systems have used round tubes, typically having a diameter of %2
inch,
3/8 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 mutli-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
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small number of large flow area flow paths extending between the inlet and
outlet
headers.
[0007] 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.
[0008] One solution to control refrigeration flow distribution through
parallel tubes in an evaporative heat exchanger is disclosed in U.S. Patent
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.
[0009] 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.
[0010] 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
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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.
[0011] 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 Invention
[0012] It 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.
[0013] 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.
[0014] It is an object of one aspect of the invention to distribute
refrigerant
to the individual channels of an array of mutli-channel tubes in a relatively
uniform
manner.
[0015] 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 mutli-
channel
tubes.
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[0016] 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.
[0017] 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.
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Brief Description of the Drawings
[0018] For 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:
[0019] Figure 1 is a perspective view of an embodiment of a heat exchanger
in accordance with the invention;
[0020] Figure 2 is a perspective view, partly sectioned, taken along line 2-2
of Figure 1;
[0021] Figure 3 is a sectioned elevation view taken along line 3-3 of
Figure 2;
[0022] Figure 4 is a sectioned view taken along line 4-4 of Figure 3;
[0023] Figure 5 is a sectioned view taken along line 5-5 of Figure 3;
[0024] Figure 6 is a perspective view, partly sectioned, of an another
embodiment of a heat exchanger in accordance with the invention;
[0025] Figure 7 is a sectioned view taken along line 7-7 of Figure 6;
[0026] Figure 8 is a sectioned view taken along line 8-8 of Figure 7;
[0027] Figure 9 is a schematic illustration of a refrigerant vapor compression
system incorporating the heat exchanger of the invention;
[0028] Figure 10 is a schematic illustration of another refrigerant vapor
compression system incorporating the heat exchanger of the invention;
[0029] Figure 11 is an elevation view, partly in section, of an embodiment of
a multi-pass evaporator in accordance with the invention; and
[0030] Figure 12 is an elevation view, partly in section, of an embodiment of
a multi-pass condenser in accordance with the invention.
Detailed Description of the Invention
[0031] The heat exchanger 10 of the invention will be described in general
herein with reference to the illustrative single pass, parallel-tube
einbodiment of a
mutli-channel tube heat exchanger as depicted in Figure 1. In the illustrative
embodiment of the heat exchanger 10 depicted in Figure 1, the heat exchange
tubes
40 are shown arranged in parallel relationship extending generally vertically
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between a generally horizontally extending inlet header 20 and a generally
horizontally extending outlet header 30. However, the depicted embodiment is
illustrative and not limiting of the invention. It is to be understood that
the invention
described herein may be practiced on various other configurations of the heat
exchanger 10. For example, the heat exchange tubes may be arranged in parallel
relationship extending generally horizontally between a generally vertically
extending inlet header and a generally vertically extending outlet header. As
a
further example, the heat exchanger could have a toroidal inlet header and a
toroidal
outlet header of a different diameter with the heat exchange tubes extend
either
somewhat radially inwardly or somewhat radially outwardly between the toroidal
headers. The heat exchange tubes may also be arranged in parallel tube, multi-
pass
embodiments, as will be discussed in further detail later herein with
reference to
Figures 11 and 12.
[0032] Referring now to Figures 1 - 5 in particular, the heat exchanger 10
includes an inlet header 20, an outlet header 30, and a plurality of
longitudinally
extending multi-channel heat exchanger tubes 40 thereby providing a plurality
of
fluid flow paths between the inlet header 20 and the outlet header 30. Each
heat
exchange tube 40 has an inlet 43 at one end in fluid flow communication to the
inlet
header 20 through a connector 50 and an outlet at its other end in fluid flow
communication to the outlet header 30. Each heat exchange tube 40 has a
plurality
of parallel flow channels 42 extending longitudinally, i.e. along the axis of
the tube,
the length of the tube thereby providing multiple, independent, parallel flow
paths
between the inlet of the tube and the outlet of the tube. Each multi-channel
heat
exchange tube 40 is a "flat" tube of, for instance, rectangular or oval cross-
section,
defining an interior which is subdivided to form a side-by-side array of
independent
flow channels 42. The flat, multi-channel tubes 40 may, for example, have a
width
of fifty millimeters or less, typically twelve to twenty-five millimeters, and
a height
of about two millimeters or less, as compared to conventional prior art round
tubes
having a diameter of %2 inch, 3/8 inch or 7 mm. The tubes 40 are shown in
drawings
hereof, for ease and clarity of illustration, as having twelve channels 42
defining
flow paths having a circular cross-section. However, it is to be understood
that in
commercial applications, such as for example refrigerant vapor compression
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systems, each multi-channel tube 40 will typically have about ten to twenty
flow
channels 42, but may have a greater or a lesser multiplicity of channels, as
desired.
Generally, each flow channel 42 will have a hydraulic diameter, defined as
four
times the flow area divided by the perimeter, in the range from about 200
microns to
about 3 millimeters. Although depicted as having a circular cross-section in
the
drawings, the channels 42 may have a rectangular, triangular, trapezoidal
cross-
section or any other desired non-circular cross-section.
[00331 Each of the plurality of heat exchange tubes 40 of the heat exchanger
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
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.
[0034] In the embodiment depicted in Figures 1, 2 and 3, the inlet header 20
comprises a longitudinally elongated, hollow, closed end cylinder having a
circular
cross-section. The inlet end 52 of each connector 50 is mated with a
corresponding
slot 26 provided in and extending through the wall of the inlet header 20 with
the
inlet end 52 of the connector 50 inserted into its corresponding slot. Each
connector
may be brazed, welded, soldered, adhesively bonded, diffusion bonded or
otherwise
secured in a corresponding mating slot in the wall of the header 20. However,
the
inlet header 20 is not limited to the depicted configuration. For example, the
header
20 might comprise a longitudinally elongated, hollow, closed end cylinder
having an
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elliptical cross-section or a longitudinally elongated, hollow, closed end
pipe having
a square, rectangular, hexagonal, octagonal, or other cross-section.
[0035] In the embodiment depicted in Figures 6, 7 and 8, the inlet header 20
comprises a longitudinally elongated, hollow, closed end, half cylinder shell
having
a generally semi-circular cross-section and a block-like insert 58 that is
brazed,
welded, adhesively bonded or otherwise secured to the open face of the half
cylinder
shell. In this embodiment, instead of a plurality of connectors 50, the
longitudinally,
extending block-like insert 58 forms a single connector 50. A plurality of
longitudinally spaced, parallel flow paths 55 is formed within the block-like
structure of the connector 50. Each flow path 55 has an inlet end 52 having at
least
one relatively small flow area inlet opening 51 in fluid communication with a
fluid
chamber 25 defined within the header 20 and an outlet end 54 having an opening
53
adapted to receive the inlet end 42 of a heat exchange tube 40. Therefore, in
this
embodiment, a plurality of heat exchange tubes 40 are connected to the header
by
means of a single block-like connector 50. The block-like insert 58 provides a
connector 50 having a plurality of flow restrictions, with at least one
relatively small
flow area opening 51 in operative association 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.
[0036] In the embodiment depicted in Figures 2, 3 and 5, only one first
opening 51 of relatively small flow area is provided in the inlet end 52 of
each
connector 50. However, it is to be understood that, if desired, more than one
first
opening 51 of relatively small flow area may be provided at the inlet end 52
of the
connector 50. For example, when the heat exchange tubes are relatively wide
and/or
have a relatively large number of channels, it may be desirable to have two,
three or
even more relatively small flow area first openings 51 disposed at spaced
intervals in
the inlet end 52 of the connector 50, such as illustrated in Figures 6, 7 and
8, to
ensure uniform distribution of fluid flow to the multiplicity of flow channels
42 of
the tube 40 inserted in the outlet end 54 of the connector 50.
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[0037] 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 Figure 3 and in Figure 7, diverge in the
direction of fluid flow from the inlet opening 51 to the outlet opening 53. A
divergent flow path assists in distributing the fluid flowing through the flow
path 55
uniformly amongst the various flow channels 42 of the heat exchange tube 40
inserted into the outlet end 54 of the connector 50, particularly in
refrigerant flow
applications wherein the fluid is a liquid refrigerant and vapor refrigerant
mixture or
expands to a liquid refrigerant/vapor refrigerant mixture as the fluid passes
through
the relatively small flow area opening or openings 51.
[0038] Referring now to Figures 9 and 10, there is depicted schematically a
refrigerant vapor compression system 100 having a compressor 60, the heat
exchanger 10A, functioning as a condenser, and the heat exchanger l OB,
functioning
as an evaporator, connected in a closed loop refrigerant circuit by
refrigerant lines
12, 14 and 16. As in conventional refrigerant vapor compression systems, the
compressor 60 circulates hot, high pressure refrigerant vapor through
refrigerant line
12 into the inlet header 120 of the condenser 10A, and thence through the heat
exchanger tubes 140 of the condenser 10A wherein the hot refrigerant vapor
condenses to a liquid as it passes in heat exchange relationship with a
cooling fluid,
such as ambient air which is passed over the heat exchange tubes 140 by a
condenser
fan 70. The high pressure, liquid refrigerant collects in the outlet header
130 of the
condenser 10A and thence passes through refrigerant line 14 to the inlet
header 20 of
the evaporator 10B. The refrigerant thence passes through the heat exchanger
tubes
40 of the evaporator 10B wherein the refrigerant is heated as it passes in
heat
exchange relationship with air to be cooled which is passed over the heat
exchange
tubes 40 by an evaporator fan 80. The refrigerant vapor collects in the outlet
header
30 of the evaporator 10B and passes therefrom through refrigerant line 16 to
return
to the compressor 60 through the suction inlet thereto. Although the exemplary
refrigerant vapor compression cycles illustrated in Figures 9 and 10 are
simplified
air conditioning cycles, it is to be understood that the heat exchanger of the
invention may be employed in refrigerant vapor compression systems of various
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designs, including, without limitation, heat pump cycles, economized cycles
and
refrigeration cycles.
[0039] In the embodiment depicted in Figure 9, the condensed refrigerant
liquid passes from the condenser 10A directly to the evaporator 10B without
traversing an expansion device. Thus, in this embodiment the refrigerant
typically
enters the inlet header 20 of the evaporative heat exchanger 10B as a high
pressure,
liquid refrigerant, not as a fully expanded, low pressure, refrigerant
liquid/vapor
mixture, as in conventional refrigerant compression systems. Thus, in this
embodiment, expansion of the refrigerant occurs within the evaporator l OB of
the
invention as the refrigerant passes through the relatively small area opening
or
openings 51 at the inlet end 52 into the flow path 55 of the connector 50,
thereby
ensuring that expansion occurs only after the distribution has been achieved
in a
substantially uniform manner.
[0040] In the embodiment depicted in Figure 10, the condensed refrigerant
liquid passes through an expansion valve 50 operatively associated with the
refrigerant line 14 as it passes from the condenser 10A to the evaporator 10B.
In the
expansion valve 50, the high pressure, liquid refrigerant is partially
expanded to
lower pressure and lower temperature, liquid refrigerant or a liquid/vapor
refrigerant
mixture. In this embodiment, the final expansion of the refrigerant is
completed
within the evaporator l OB as the refrigerant passes through the relatively
small flow
area opening or openings 51 at the inlet end 52 into the flow path 55 of the
connector 50. Partial expansion of the refrigerant in an expansion valve
upstream of
the inlet header 20 to the evaporator l OB may be advantageous when the cross-
sectional flow area of the openings 51, can not be made small enough to ensure
complete expansion as the liquid passes through the openings 51 or when an
expansion valve is used as a flow control device.
[0041] Referring now to Figure 11, the heat exchanger 10 of the invention is
depicted in a multi-pass, evaporator embodiment. In the illustrated multi-pass
embodiment, the inlet header 20 is partitioned into a first chamber 20A and a
second
chamber 20B, the outlet header is also partitioned into a first chamber 30A
and a
second chamber 30B, and the heat exchange tubes 40 are divided into three
banks
40A, 40B and 40C. The tubes of the first tube bank 40A have inlet ends
inserted
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into respective connectors 50A that are open into the first chamber 20A of the
inlet
header 20 and outlet ends are open to the first chamber 30A of the outlet
header 30.
The tubes of the second tube bank 40B have inlet ends inserted into respective
connectors 50B that are open into the first chamber 30A of the outlet header
30 and
outlet ends are open to the second chamber 20B of the inlet header 20. The
tubes of
the third tube bank 40C have inlet ends inserted into respective connectors
50C that
open into the second chamber 20B of the inlet header 20 and outlet ends are
open to
the second chamber 30B of the outlet header 30. In this manner, refrigerant
entering
the heat exchanger from refrigerant line 14 passes in heat exchange
relationship with
air passing over the exterior of the heat exchange tubes 40 three times,
rather than
once as in a single pass heat exchanger. In accord with the invention, the
inlet end
43 of each of the tubes of the first, second and third tube banks 40A, 40B and
40C is
inserted into the outlet end 54 of its associated connector 50 whereby the
channels
42 of each of the tubes 40 will receive a relatively uniform distribution of
expanded
refrigerant liquid/vapor mixture. Distribution and expansion of the
refrigerant
occurs as the refrigerant passes from the header into the connector through
the
relatively small cross-sectional flow area opening 51, not only as the
refrigerant
passes into the first tube bank 40A, but also as the refrigerant passes into
the second
tube bank 40B and into the third tube bank 40C, thereby ensuring more uniform
distribution of the refrigerant liquid/vapor upon entering the flow channels
of the
tubes of each tube bank.
[0042] Referring now to Figure 12, the heat exchanger 10 of the invention is
depicted in a multi-pass, condenser embodiment. In the illustrated multi-pass
embodiment, the inlet header 120 is partitioned into a first chamber 120A and
a
second chamber 120B, the outlet header 130 is also partitioned into a first
chainber
130A and a second chamber 130B, and the heat exchange tubes 140 are divided
into
three banks 140A, 140B and 140C. The tubes of the first tube bank 140A have
inlet
end openings into the first chamber 120A of the inlet header 120 and outlet
end
openings to the first chamber 130A of the outlet header 130. The tubes of the
second tube bank 140B have inlet ends inserted into respective connectors 50B
that
are open into the first chamber 130A of the outlet header 130 and outlet ends
that are
open to the second chamber 120B of the inlet header 120. The tubes of the
third
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tube bank 140C have inlet ends inserted into respective connectors 50C that
are open
into the second chamber 120B of the inlet header 120 and outlet ends are open
to the
second chamber 130B of the outlet header 130. In this manner, refrigerant
entering
the condenser from refrigerant line 12 passes in the heat exchange
relationship with
air passing over the exterior of the heat exchange tubes 140 three times,
rather than
once as in a single pass heat exchanger. The refrigerant entering the first
chamber
120A of the inlet header 120 is entirely high pressure, refrigerant vapor
directed
from the compressor outlet via refrigerant line 14. However, the refrigerant
entering
the second tube bank and the third tube bank typically will be a liquid/vapor
mixture
as refrigerant partially condenses in passing through the first and second
tube banks.
In accord with the invention, the inlet end of each of the tubes of the second
and
third tube banks 140B, 140C is inserted into the outlet ends of their
associated
connectors 50B, 50C whereby the chaimels 42 of each of the tubes will receive
a
relatively uniform distribution of expanded refrigerant liquid/vapor mixture.
Obviously, it has to be noted that pressure drop through the openings 51 has
to be
limited to not exceed a predetermined threshold for the condenser
applications, in
order not to compromise the heat exchanger efficiency. Further, a person
ordinarily
skilled in the art would understand that other multi-pass arrangements for
condensers and evaporators are also within the scope of the invention.
[0043] 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.
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