Note: Descriptions are shown in the official language in which they were submitted.
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PLUG BYPASS VALVES AND HEAT EXCHANGERS
This invention relates to heat exchangers, and in particular, to bypass
valves for bypassing or short-circuiting flow from the heat exchanger inlet to
the
heat exchanger outlet under conditions where the heat transfer function of the
heat exchanger is not required or is only intermittently required.
In certain applications, such as in the automotive industry, heat
exchangers are used to cool or heat certain fluids, such as engine oil or
transmission fluid or oil. In the case of transmission fluid, for instance, a
heat
exchanger is usually used to cool the transmission fluid. The heat exchanger
is
usually located remote from the transmission and receives hot transmission
fluid
from the transmission through supply tubing, cools it, and delivers it back to
the
transmission again through return tubing. However, when the transmission is
cold, such as at start-up conditions, the transmission oil is very viscous and
does not flow easily through the heat exchanger, if at all. In such cases, the
transmission can be starved of fluid and this may cause damage to the
transmission or at least erratic performance. Damage can also be caused to the
transmission if the quantity of fluid returned is adequate, but is over-cooled
by
the heat exchanger due to low ambient temperatures. In this case, water may
accumulate in the transmission fluid as a result of condensation (which
normally
would be vaporized at higher temperatures) and this may cause corrosion
damage or transmission fluid degradation.
In order to overcome the cold flow starvation problem, it has been
proposed to insert a bypass valve between the supply and return tubing to and
from the heat exchanger. This bypass valve may be temperature responsive so
that it opens causing bypass flow when the transmission fluid is cold, and it
closes to prevent bypass flow when the transmission fluid heats up to
operating
temperature. An example of such a bypass valve is shown in U.S. Patent No.
6,253,837 issued to Thomas F. Seiler et al. While this approach works
satisfactorily, the heat exchanger and bypass valve assembly becomes quite
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large and includes fluid inlet and outlet tubing that may not otherwise be
required.
In the present invention, the bypass valve can be incorporated as an
integral part of the heat exchanger as a plug-in item that can be located
anywhere desired between the inlet and outlet flow manifolds of the heat
exchanger.
According to one aspect of the invention, there is provided a bypass
valve for a heat exchanger including a plurality of parallel, tubular members
having adjacent wall portions defining flow openings in communication to form
flow manifolds. The bypass valve comprises a housing having a hollow plug
portion with opposed plug walls defining inlet and outlet openings therein,
the
plug walls being adapted to be sealingly mounted between selected adjacent
tubular member wall portions to allow fluid flow respectively between the flow
manifolds and the inlet and outlet openings. The housing also has an actuator
portion located adjacent to the plug portion. Also, an actuator is releasably
mounted in the actuator portion and has a reciprocating plunger extending into
the plug portion to block and unblock flow between the inlet and outlet
openings.
According to another aspect of the invention, there is provided a heat
exchanger comprising a plurality of parallel, tubular members having adjacent
wall portions defining flow openings in communication to form inlet and outlet
manifolds for the flow of fluid through the tubular members. A bypass valve
includes a housing having a hollow plug portion with opposed plug walls
defining inlet and outlet openings therein, the plug walls being sealingly
mounted between selected adjacent tubular member wall portions to allow fluid
flow respectively between the flow manifolds and the inlet and outlet
openings.
The housing also has an actuator portion located adjacent to the plug portion.
Also, an actuator is releasably mounted in the actuator portion and has a
reciprocating plunger extending into the plug portion to block and unblock
flow
between the inlet and outlet openings.
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Preferred embodiments of the invention will now be described by way of
example, with reference to the accompanying drawings, in which:
Figure 1 is an elevational view of a heat exchanger having a preferred
embodiment of a bypass valve according to the present invention mounted
therein;
Figure 2 is an enlarged view of the portion of Figure 1 indicated by circle
2;
Figure 3 is a perspective view, partly broken away of the bypass valve of
Figure 2 shown in the closed position;
Figure 4 is a perspective view similar to Figure 3 but showing the bypass
valve in the open position;
Figure 5 is an elevational view similar to Figure 2, but showing another
preferred embodiment of a bypass valve according to the present invention, the
valve being shown partially in cross-section;
Figure 6 is an elevational view similar to Figure 2, yet showing another
preferred embodiment of a bypass valve according to the present invention, the
valve being shown in cross-section and in the closed position;
Figure 7 is an elevational view similar to Figure 6, but showing the
bypass valve of Figure 6 in the open position;
Figure 8 is a schematic view of a heat exchanger having multiple passes
and more than one bypass valve; and
Figure 9 is an elevational view of a portion of another preferred
embodiment of a heat exchanger and bypass valve according to the present
invention.
Referring firstly to Figures 1 and 2, a heat exchanger is generally
indicated by reference in 10, and a preferred embodiment of a bypass valve
according to the present invention is generally indicated by reference numeral
12. Heat exchanger 10 is formed of a plurality of parallel, spaced-apart,
tubular
members 14 preferably with enlarged distal end portions 16 that have adjacent
wall portions 17 defining flow openings (not shown) in communication. Tubular
members 14 are preferably formed of mating plate pairs with transversely
CA 02354217 2001-07-26
protruding cupped end portions to form these enlarged end portions 16 that
also
together form flow manifolds 19 and 21. However, tubular members 14 could be
formed of tubes with separate joined enlarged end portions 16, if desired.
Alternatively, tubular members of uniform width or thickness could be used, in
which case tubular spacers could be used between the tube ends in place of
enlarged distal end portions 16. If it is not necessary to space tubular
members
14 apart transversely, then such spacers would not be required. Yet another
possibility would be to use transversely orientated tubular manifolds 19 and
21
attached in communication with the ends of tubular members 14. For the
purpose of this disclosure, the term "distal end portions" is intended to
include
all of the above-mentioned tube member communicating wall structures.
Corrugated cooling fins 18 are located between the tubular members 14 where
the tubular members 14 are spaced apart transversely.
In the heat exchangers shown in Figures 1 and 2, the tubular members
14 are formed into two upper and lower groups separated by central back-to-
back dimpled plates 20 having offset end portions 22, 24. As seen best in
Figure 2, the space between offset end portions 22, 24 provides a location
where bypass valve 12 can be plugged into heat exchanger 10. Bypass valve
12 includes a hollow plug portion 26 located in this space, and which will be
described in further detail below.
As mentioned above, the enlarged distal end portions 16 have transverse
openings therethrough (not shown), so that the distal end portions 16 located
above bypass valve 12 are all in communication and form either an inlet or an
outlet manifold 19 depending on the direction in which fluid is to flow
through
heat exchanger 10. Similarly, the enlarged distal end portions 16 located
below
bypass valve 12 are all in communication and form a respective outlet or inlet
manifold 21. As seen best in Figure 1, an inlet or outlet fitting 28
communicates
with the enlarged distal end portions below it and an inlet or outlet fitting
30
communicates with the enlarged distal end portions above it. So, for example,
fluid entering inlet fitting 28 travels from right to left as shown in Figure
1
through all of the tubular members 14 located above dimpled plates 20, to a
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similar left hand manifold formed by enlarged distal end portions 32, and then
downwardly through a cross-over fitting 34 into a left hand manifold in the
lower
section of heat exchanger 10 formed by enlarged distal end portions 32, and
then back to the right end and out through outlet fitting 30. Heat exchanger
10
is thus called a two-pass heat exchanger and can have any number of tubular
members 14 above or below the dimpled plates 20. In fact, there could just be
one tubular member 14 above or below dimpled plates 20, as illustrated in the
embodiment shown in Figure 9 and as described further below.
Heat exchanger 10 also has upper and lower dimpled plates 36. Suitable
mounting brackets 40 are attached to dimpled plates 36, 38 as are the inlet
and
outlet fittings 28, 30.
Referring next to Figures 3 and 4, bypass valve 12 includes a housing 42
having a hollow plug portion 26 with spaced-apart, opposed, flat, parallel
plug
side walls 43 defining transversely located inlet and outlet openings 44, 46
formed therein for the flow of fluid through plug portion 26 when valve 12 is
in
the open position as shown in Figure 4. Plug walls 43 are sealingly mounted
between selected adjacent tubular member wall portions 17 of the enlarged
distal end portions 16 of tubular members 14. The distal end portions 16 have
flat mating surfaces. The offset end portions 22 mate flush against their
adjacent
distal end portion flat surfaces and the flat housing side walls 43 mate flush
against the flat offset end portions 22. However, housing side or plug walls
43
would mate flush against the flat portions of distal end portions 16, if
dimpled
plates 22 were not used in heat exchanger 10. This mounting allows bypass
fluid flow directly between selected distal end portions 16, or respectively
between the flow manifolds 19 and 21 and the inlet and outlet openings 44 and
46, or between the inlet and outlet fittings 28, 30 when bypass valve 12 is
open.
Bypass valve side or plug walls 43 are spaced apart a predetermined distance
so as to determine the spacing between adjacent heat exchanger tubular
members, especially if dimpled plates 20 are not used.
Bypass valve housing 42 also has an actuator portion 48 located
adjacent to and communicating with plug portion 26. A temperature responsive
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actuator 50 is located in housing 42. Actuator 50 has a central shaft 52
attached to a
removable closure 54 located remote from plug portion 26. Removable closure 54
has an O-ring seal 56 and is held in position by a split pin 58 passing
through
openings 60 in housing actuator portion 40 and a through hole 62 in closure
54.
Temperature responsive actuator 50 has a reciprocating barrel portion 64
which forms a plunger slidably located in housing plug portion 26 to block and
unblock flow between inlet and outlet openings 44, 46. A spring 66 is located
in
housing actuator portion 48 and bears against an annular shoulder 68 on barrel
64 to
act as bias means to urge the actuator 50 to retract so that barrel or plunger
64
unblocks the flow of fluid through inlet and outlet openings 44, 46 of bypass
valve 12,
when the actuator is not extended due to temperature, as described next below.
Temperature responsive actuator 50 is sometimes referred to as a thermal
motor and it is a piston and cylinder type device. Barrel or plunger 64 is
filled with a
thermal sensitive material, such as wax, that expands and contracts, causing
the
actuator to extend axially upon being heated to a predetermined temperature
and to
retract upon being cooled below this predetermined temperature. Where bypass
valve 12 is used in conjunction with an automotive transmission fluid or oil
cooler,
this predetermined temperature is about 80°C, which is the temperature
of the fluid
from the transmission when bypass flow is no longer required.
Referring next to Figure 5, another preferred embodiment of a bypass valve
according to the present invention is generally indicated by reference numeral
70.
Bypass valve 70 is similar to bypass valve 12 except that a sliding plate 72
bears
against central shaft 52 and a spring 74 is located in housing actuator
portion 48 to
urge central shaft 52 toward the housing plug portion 26. Spring 74 absorbs
any
pressure spikes or peeks that may occur in the inlet and outlet manifolds of
heat
exchanger 10. A notch 76 is formed in barrel 64 to allow the fluid to act
against the
end of barrel 64 and provide this pressure relief even when bypass valve 70 is
closed. A bleed hole through plunger or barrel 64
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communicating with inlet opening 44 could also be used in place of notch 76
for
this purpose. Otherwise, bypass valve 70 is substantially the same as bypass
valve 12.
Referring next to Figures 6 and 7, another preferred embodiment of a
bypass valve according to the present invention is generally indicated by
reference numeral 80. In bypass valve 80, the temperature responsible actuator
50 includes a solenoid having a solenoid coil 82 and a central actuator shaft
84
attached to a plunger 86. Plunger 86 also has a notch or bleed hole 76 to
provide pressure spike relief when valve 80 is closed. Actuator shaft 84
extends upon energization of solenoid coil 82, so that plunger 86 blocks flow
between the housing inlet and outlet openings 44, 46. A spring 88 located in
housing plug portion 26 bears against plunger 86 to act as bias means for
urging the actuator shaft 84 to retract upon the energization of solenoid coil
82.
A temperature sensor 90 is attached to plunger 86 and is in the form of a
thermistor electrically coupled to solenoid coil 82 for actuation of the
solenoid
coil when the temperature of the fluid going through heat exchanger 10 reaches
a predetermined temperature. Temperature sensor 90 could be located
elsewhere in bypass valve 80, or even elsewhere in heat exchanger 10.
Preferably, temperature sensor 90 is electrically connected to an electrical
control circuit 92 mounted in housing actuator portion 48. Electrical control
circuit 92 is in turn is electrically connected to solenoid coil 82 for
controlling the
movement of plunger 86 in accordance with the temperature sensed by
temperature sensor 90. In this way, the opening of bypass valve 80 could be
controlled to provide variable opening, rather than a simple on or off, but
the
latter is also possible.
Referring next to Figure 8, a heat exchanger 100 is shown schematically
and it is like two heat exchangers 10 of Figure 1 mounted in series. Two
bypass
valves 102, 104 are used to provide thermal modulation of the fluid flowing
through the heat exchanger 100. Bypass valve 102 may have a predetermined
temperature set point or activation temperature, and bypass valve 104 may
have a somewhat higher temperature set point or activation temperature. Heat
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exchanger 100 is a four pass heat exchanger having four groups or stacks 106,
108, 110 and 112 of tubular members.
Where both bypass valves 102 and 104 are open, such as during cold
flow operation, there is full fluid bypass from inlet fitting 28 to outlet
fitting 30.
Where bypass valve 102 is closed and valve 104 is open, such as during warm
up or an interim temperature of fluid flowing through heat exchanger 100,
there
would be fluid flow through the top two passes 106 and 108 of heat exchanger
100, but passes 110 and 112 would be bypassed through bypass valve 104.
Where the fluid reaches its hot operating temperature, both bypass valves 102
and 104 would close giving flow through all four passes 106, 108, 110 and 112
and no bypass flow at all. Additional multiples of passes and bypass valves
could be used in a single heat exchanger as well. Any of the types of bypass
valves described above could be used in heat exchanger 100.
Referring next to Figure 9, other preferred embodiments of a heat
exchanger 113 and a bypass valve 115 are shown. In bypass valve 115, inlet
and outlet openings 44, 46 are formed in opposed plug walls 114, 116 and this
shows that inlet and outlet openings 44, 46 can be located anywhere in plug
portion 26 as long as one of these openings is blocked when valve 115 is
closed. Otherwise, bypass valve 115 is substantially similar to or can
incorporate
the features of the bypass valves 12, 70 and 80 described above. In the
embodiment of Figure 9, plate 38 (which preferably is dimpled but may be flat)
and a bottom plate 118 (which may also be dimpled or flat), together form a
tubular member 120 which is one of the tubular members that make up heat
exchanger 113. Tubular member 120 is actually a bypass channel and has flow
openings 122 that communicate with the flow openings in the adjacent enlarged
distal end portions 16 of adjacent tubular member 14, and as such forms part
of
the inlet and outlet manifolds of heat exchanger 113. Instead of tubular
member
120, a regular tubular member 14 could be used in heat exchanger 113, if
desired. This would produce a full flood or single pass heat exchanger.
Tubular
members 14 may or may not have turbulizers in them or be made of dimpled
plates, but the bottom tubular member 120 likely would not be turbulized or
have
other types of flow augmentation, such as dimples.
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In the assembly of heat exchangers 10, 100 and 113,-the various
components, such as the tubular members 14 or 120 and fins 18 are stacked
together along with dimpled plates 20, if desired, and upper and lower dimpled
plates 36, 38. Mounting plates or brackets 40 and inlet and outlet fittings
28, 30
can be preassembled to upper and lower dimpled plates 36, 38, or assembled
along with all of the other components. The housing 42 of the preferred bypass
valve 12, 70, 80 or 115 (without any other bypass valve components) is then
placed in the desired location in the heat exchanger and the entire assembly
is
brazed together in a brazing furnace. It will be appreciated that in the
preferred
embodiments, aluminum or a brazing-clad aluminum is used for most of the
parts of the heat exchangers, so that all of the parts can be brazed together
in a
brazing furnace. After this assembly is cooled, the desired actuator
components
of the bypass valves are inserted into housing 42 and the removable closures
54
are secured in position with split pins 58.
Having described preferred embodiments of the invention, it will be
appreciated that various modifications can be made to the structures described
above. For example, instead of using a thermal motor or solenoid type actuator
for the bypass valves, other devices could be used as well, such as a bi-
metallic
helix to move the barrel or plunger of the valve. The tubular members can also
have other shapes or configurations as well.
From the above, it will be appreciated that the bypass valves of the
present invention are in the form of plugs that can be plugged in at any
desired
location in the heat exchanger with a simple rearrangement of the location of
some components. The bypass valve housings actually act as a form of baffle
plate to intermittently block flow between manifold portions of the heat
exchangers. In fact, the bypass valves could be plugged in anywhere in the
heat
exchangers where it is desired to have bypass flow between the plate pairs or
tubes. The bypass valve housings are brazed in place along with all of the
other heat exchanger components. The actual valve elements in the actuators
are then removably or releasably located in the bypass valve housings to
complete the assembly. No external tubing or peripheral components are
required to make the actuator valves active.
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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
it is not to limit the scope of the invention.