Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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HEAT EXCHANGER WITH FLOW DISTRIBUTING
ORIFICE PARTITIONS
This invention relates to heat exchangers, and in particular, to heat
exchangers involving gas/liquid, two-phase flow, such as in evaporators or
condensers.
In heat exchangers involving two-phase, gas/liquid fluids, flow distribution
inside the heat exchanger is a major problem. When the two-phase flow passes
through multiple channels which are all connected to common inlet and outlet
manifolds, the gas and liquid have a tendency to flow through different
channels
at different rates due to the differential momentum and the changes in flow
direction inside the heat exchanger. This causes uneven flow distribution for
both
the gas and the liquid, and this in turn directly affects the heat transfer
performance, especially in the area close to the outlet where the liquid mass
proportion is usually quite low. Any maldistribution of the liquid results in
dry-out
zones or hot zones. Also, if the liquid-rich areas or channels cannot
evaporate all
of the liquid, some of the liquid can exit from the heat exchanger. This often
has
deleterious effects on the system in which the heat exchanger is used. For
example, in a refrigerant evaporator system, liquid exiting from the
evaporator
causes the flow control or expansion valve to close reducing the refrigerant
mass
flow. This reduces the total heat transfer of the evaporator.
In conventional designs for evaporators and condensers, the two-phase
flow enters the inlet manifold in a direction usually perpendicular to the
main heat
transfer channels. Because the gas has much lower momentum, it is easier for
it to
change direction and pass through the first few channels, but the liquid tends
to
keep traveling to the end of the manifold due to its higher momentum. As a
result,
the last few channels usually have much higher liquid flow rates and lower gas
flow rates than the first one. Several methods have been tried in the past to
even
out the flow distribution in evaporators. One of these is the use of an
apertured
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inlet manifold as shown in United States Patent No. 3,976,128 issued toPatel
et al.
Another approach is to divide the evaporator up into zones or smaller
groupings of the flow channels connected together in series, such as is shown
in
U.S. Patent No. 4,274,482 issued to Noriaki Sonoda. While these approaches
tend
to help a bit, the flow distribution is still not ideal and inefficient hot
zones still
result.
In the present invention, barriers or partitions are used in the inlet
manifold
to divide the heat exchanger into sections. The barriers have orifices to
allow a
predetermined proportion of the flow to pass through to subsequent sections,
so
that the flow in the sequential sections is maintained in parallel and more
evenly
distributed.
According to the invention, there is provided a heat exchanger comprising
a first plurality of stacked, tube-like members having respective first inlet
and outlet
distal end portions defining respective inlet and outlet openings. All of the
first
inlet openings are joined together so that the inlet distal end portions form
a first
inlet manifold, and all of the first outlet openings are joined together so
that the first outlet distal end portions form a first outlet manifold. A
second plurality of stacked,
tube-like members is located adjacent to the first plurality of tube-like
members.
The second plurality of tube-like members has second inlet and outlet distal
end
portions defining respective second inlet and outlet openings. All of the
second
inlet openings are joined together so that the second inlet distal end
portions form a
second inlet manifold and all of the second outlet openings are joined
together so
that the second outlet distal end portions form a second outlet manifold. The
second
outlet manifold is joined to communicate with the first outlet manifold. The
second
inlet manifold is joined to communicate with the first inlet manifold. A first
barrier
is located between the first and second inlet manifolds. The barrier defines a
first
orifice to permit a portion only of the flow in the first inlet manifold to
pass into the
second inlet manifold. There is also a third plurality of stacked, tube-like
members
located adjacent to the second plurality of tube-like members, the third
plurality of
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tube-like members having a third inlet and third outlet distal end portions
defining
respective third inlet and third outlet openings. All of the third inlet
openings are
joined together so that the third inlet distal end portions form a third inlet
manifold
and all of the third outlet openings are joined together so that the third
outlet distal
end portions form a third outlet manifold. The third outlet manifold is joined
to
communicate with the second outlet manifold. The third inlet manifold is
joined to
communicate with the second inlet manifold. A second barrier is located
between
the second and third inlet manifolds, the second barrier defining a second
orifice to
permit a portion only of the flow in the second inlet manifold to pass into
the third
inlet manifold. The first orifice and the second orifice have different
configurations.
A fluid inlet tube for the heat exchanger is provided and passes through the
first,
second and third inlet manifolds and through openings provided through the
first
and second barriers, these openings being discreet from the orifices.
Preferred embodiments of the invention will now be described, by way
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example, with reference to the accompanying drawings, iri which:
Figure 1 is an elevational view of a preferred embodiment of a heat
exchanger according to the present invention;
Figure 2 is a-top or plan view of the heat exchanger shown in Figure 1;
Figure 3 is a left end view of the heat exchanger shown in Figure 1;
Figure 4 is an enlarged elevational view of one of the main core plates used
to make the heat exchanger of Figure 1;
Figure 5 is a left side or edge view of the plate shown in Figure 4;
Figure 6 is7 an enlarged sectional view taken along lines 6-6 of Figure 4;
Figure 7 is a plan view of one type of barrier or partition shim plate used in
the heat exchanger shown in Figures 1 to 3;
Figure 8 is an enlarged sectional view taken along lines 8-8 of Figure 7;
Figure 9 is a left end view of the barrier plate shown in Figure 7;
Figure 10 is a front or elevational view of the barrier plate shown in Figure
7;
Figure 11 is a plan view, similar to Figure 7, but showing another type of
barrier or partition plate used in the heat exchanger of Figures 1 to 3;
Figure 12 is plan view, similar to Figures 7 and 11, but showing yet another
type of barrier or partition piate used in the heat exchanger of Figures 1, to
3;
Figure 13 is an elevational view, similar to Figure 4, but showing another
type of core plate used in the heat exchanger of Figures 1 to 3;
Figure 14 is an elevational view similar to Figures 4 and 13, but showing
yet another type of core plate used in the heat exchanger of Figures 1 to 3;
Figure 15 is an enlarged sectional view taken along lines 15-15 of Figure
14;
Figure 16 is an elevational view similar to Figures 4, 13 and 14, but
showing yet another type of core plate used in the heat exchanger of Figures I
to
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3;
Figure 17 is an enlarged scrap view of the area indicated by circle 5 in
Figure 16, but showing a modification to the location of the orifice;
Figure 18 is a scrap view similar to Figures 17 but showing yet another
modification to the flow orifice;
Figure 19 is a scrap view similar to Figure 17 and 18 but showing yet
another modification to the flow orifice;
Figure 24 is a scrap view similar to Figures 17 to 19 but showing yet
another modification to the flow orifice;
Figure 21 is a diagrammatic perspective view taken from the front and
from the right side showing.the flow path inside the heat exchanger of Figures
1 to
3;
Figure 22 is a perspective view similar to Figure 21, but taken from the rear
and from the left side of the heat exchanger of Figures 1 to 3;
Figure 23 is a perspective view similar to Figures 21 and 22, but illustrating
the flow path in another preferred embodiment of the present invention;
Figure 24 is a scrap view similar to Figure 17, but showing a portion of one
of the core plates that is used in the embodiment of Figure 23;
Fig-are 25 is a scrap view similar to Figure 24 but showing a modified type
of orifice;
Figure 26 is a scrap view similar to Figures 24 and 25, but showing yet
another modirication to the orifice;
Figure 27 is a scrap view similar to Figures 24 to 26, but showing yet
another modification to the onfice; and
Figure 28 is an elevational view of a core plate that is used in another
preferred embodiment of the invention where the inlet and outlet manifolds are
located at opposed ends of the core plate, rather than being adjacent as in
the
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embodiments shown in Figures 1 to 3.
Referring firstly to Figures 1 to 6, a preferred embodiment of the present
invention is made up of a plurality of plate pairs 20 formed of back-to-back
plates
14 of the type shown in Figures 4 to 6. These are stacked, tube-like members
having enlarged distal end portions or bosses 22, 26 having inlet 24 and
outlet 30
openings, so that the flow travels in a U-shaped path through the plate pairs
20.
Each plate 14 preferably includes a plurality of evenly spaced dimples 6
projecting into the flow channel created by each plate pair 20. Preferably,
fins 8
are located between adjacent plate pairs. The bosses 22 on one side of the
plate
are joined together to form an inlet manifold 32 and the bosses 26 on the
other
side of the plates are joined together to form an outlet manifold 34, As seen
best in
Figure 2, a longitudinal tube 15 passes into the inlet manifold openings 24 in
the
plates to deliver the incoming fluid, such as a two-phase, gas/liquid mixture
of
refrigerant, to the right hand section of the heat exchanger 10. Figure 3
shows end
plate 35 with an end fitting 37 having openings 39, 41 in communication with
the
inlet manifold 32 and outlet manifold 34, respectively.
The heat exchanger 10 is divided into plate pair sections A, B, C, D, E by
placing barrier or partition plates 7, 11, 12, such as are shown in Figures 7
to 12,
between selected plate pairs in the heat exchanger. The inlet and outlet
manifolds
formed in the plate pairs of each section may be considered separate manifolds
from each other, the inlet manifolds of adjacent sections being joined to
communicate with one another and the outlet manifolds of adjacent sections
being
joined to communicate with one another. For example the inlet manifold 32 of
section C is joined to communicate with the inlet manifold of section D and
the
outlet rnanifold of section C is joined to communicate with the outlet
manifold of
section D. Referring to Figures 21 and 22, sections are shown schematically,
and
the dividing walls represent actual barrier plates 7, 11, and 12 as shown in
Figures
7, 11 and 12. As shown in Figures 7 to 12, each barrier may have an end flange
or
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flanges 42 positioned such that the barrier plates can be distinguished from
one
another when positioned in the heat exchanger. For example barrier plate 7 has
two end flanges 42, barrier plate 11 has a lower positioned end flange 42 and
barrier plate 12 has an upper positioned end flange 42. The direction of flow
is
indicated with arrows. Referring again to Figures 21 and 22, an inlet tube 15
delivers the fluid through an inlet 18 to the right hand section A of the heat
exchanger where it would travel down along the back, or along the right hand
side
of the plates 14 as seen in Figure 4, cross over_ and travel up the front, or
along the
left hand side of the plates as seen in Figure 4. Barrier plates 7,12 each
include an
opening 70 to accommodate the inlet tube 15. The flow then passes through a
left
hand hole 36 of barrier 7, traveling down along the front of the next section
B of
plates, across and up the back of these plates to pass through a hole 3 8 in
barrier
plate 11 (see Figure 11) which surrounds tube 15.
Most of the flow then travels down the backside and up the front of the
next section C of the heat exchanger plates and passes out via the outlet
manifold
through an outlet hole 40, which is the left hand hole of the barrier plate 12
shown
in Figure 12 through to the outlet manifold of section D. However, some of the
flow passes via the inlet manifold of section C through a small orifice 17
(see
Figure 12) and into the inlet manifold of the next section D of core plates.
In this
next section D, flow again travels down the back and up the front and out
through
the outlet hole 40 in the next barrier 12. Again some of the flow goes through
the
inlet manifold through an orifice 17 into the inlet manifold of yet another
section
E of core plates. In this last section E of core plates, the flow goes down
the back,
up the front and finally out of the heat exchanger outlet 58.
Referring again to Figure 21, it will be appreciated that in the first two
sections of core plates from the right A, B the fluid is flowing in series
through
these sections. However, when the fluid reaches the third section C, most of
it
travels in the U-shaped direction, but some of it is passed via the inlet
manifold
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through the small orifices 17 in plates 12, to the next section's inlet
manifold so
that the flow in the last three sections of core plates is in parallel. This
parallel
flow produces proportional, even flow distribution to balance the flow rate
among
all of the sections in the heat exchanger.
Rather than using the core plates of Figure 4 and the barrier or partition
plates of Figures 7 to 12, the partitions of Figures 7 to 12 could actually be
built
right in or made an integral part of the core plates 50, 52, 54 as shown in
Figures
13 to 16. Core plate 50 as shown in Figure 13_is equivalent to core plate 14
of
Figure 4 with a barrier plate 7 of Figure 7 in that it has outlet opening 30
but inlet
opening 24 includes an integral barrier 60 with a hole 70 therethrough to
accommodate tube 15. Core plate 52 of Figure 14 is equivalent to core plate 14
of
Figure 4 with a barrier plate 11 of Figure 11 in that outlet opening 30 is
blocked by
an integral barrier 62 and inlet opening 24 is not blocked. Core plate 54 of
Figure
16 is equivalent to core plate 14 of Figure 4 with a barrier or partition
plate 12 of
Figure 12 in that inlet opening 24 is blocked by an integral barrier 64 having
a
hole 70 to accommodate tube 15 and an orifice 17 thereby allowing a portion of
flow to pass through the inlet manifold to the next section. It will be
appreciated
that the core plates of Figure 13 and Figure 14 would be used in the Figure 21
embodiment in the location of the respective partitions 7 and 11. The core
plate
shown in Figure 16 would be used where the partitions 12 are indicated in
Figure
21.
Figures 17 to 20 show different configurations of orifices 17 in core plates
that would be used in the location of barriers 12 in the embodiment of Figure
21.
The different orifices 17 are used to balance the flow rates amongst all of
the
sections in the manifold. The flow rates can be controlled by adjusting the
sizes or
locations (top or bottom) or the shapes of the orifices, such as round,
vertical slot,
horizontal slot or any other configuration. The location of the orifice high
or low
on the partition or core plate can be used to adjust the proportion of liquid
to gas
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phase within the flow that is passed through the orifice, while the size of
the hole
is used more to adjust the overall mass flow rate. The sensitivities of the
orifice
size and location will tend to be application-specific, depending on how well
mixed the two phases of the flow are at the point of flow splitting. Also,
rather
than one orifice hole, several smaller holes would be used. Further, the
orifice in
the first partition plate could be larger, or there could be more orifices,
than in the
second or down stream partition or barrier.
In the embodiment represented by Figure 23, it will be noted that there is
no longitudinal inlet tube. The flow as indicated with arrows enters the left
side of
the heat exchanger, travels in series through the first two sections, and then
in
parallel through the last three sections in a manner similar to that of the
embodiment of Figures 21 and 22. In this Figure 23 embodiment, it will also be
noted that the inlet 18 and outlet 58 are at opposite ends of the heat
exchanger,
rather than being adjacent as in the embodiment of Figures 21 and 22. In the
embodiment of Figure 23, the core plates would not have holes to accommodate a
longitudinal inlet tube, as indicated in Figures 24 to 27. Similar
modifications will
be made to the barrier or partition plates 7, 11, 12 of' Figures 7 and 12, if
such
barriers are used with the core plates 14 of Figure 4 to make a heat exchanger
as
indicated in Figure 23.
As mentioned above, the flow through the core plates travels in a U-shaped
path in the embodiments of Figures 1 to 27. However, this U-shaped path could
be, in effect, straightened out, in which case core plates 56 as shown in
Figure 28
would be used.
As will be apparent to those skilled in the art in the light of the foregoing
disclosure, many alterations and modifications are possible in the practice of
this
invention without departing from the spirit or scope thereof. The foregoing
description is of the preferred embodiments and is by way of example only, and
is
not to limit the scope of the invention.
