U.S. patent application number 10/891192 was filed with the patent office on 2005-01-13 for heat exchange system.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Hirakata, Syuji.
Application Number | 20050008914 10/891192 |
Document ID | / |
Family ID | 18581057 |
Filed Date | 2005-01-13 |
United States Patent
Application |
20050008914 |
Kind Code |
A1 |
Hirakata, Syuji |
January 13, 2005 |
Heat exchange system
Abstract
A heat exchange system includes a fuel cell that receives a
specified gas and generates electric power, a heat exchange device
that exchanges heat with a heat exchange medium, a heat exchange
medium passage, and a gas detector. The heat exchange medium
passage allows the heat exchange medium to circulate between the
heat exchange device and the fuel cell such that the heat exchange
medium can exchange heat with the heat exchange device and the fuel
cell. The gas detector is disposed at at least one of the heat
exchange device and the heat exchange medium passage to detect the
specified gas that leaks into the heat exchange medium.
Inventors: |
Hirakata, Syuji;
(Susono-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Aichi-ken
JP
471-8571
|
Family ID: |
18581057 |
Appl. No.: |
10/891192 |
Filed: |
July 15, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10891192 |
Jul 15, 2004 |
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09797935 |
Mar 5, 2001 |
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6800389 |
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Current U.S.
Class: |
429/435 ;
429/512 |
Current CPC
Class: |
Y02E 60/50 20130101;
H01M 8/04074 20130101; F28F 2265/16 20130101; H01M 8/04029
20130101; H01M 8/065 20130101 |
Class at
Publication: |
429/026 |
International
Class: |
F23L 015/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 2000 |
JP |
2000-060806 |
Claims
1-13. (Cancelled)
14. A heat exchange system, comprising: an exothermic body capable
of generating heat, said exothermic body being supplied with a heat
exchange medium for heat exchange therewith: a gas absorbing device
comprising a gas absorbing alloy that is able to absorb or release
a specified gas; a heat exchange device configured and positioned
to perform heat exchange with the heat exchange medium; a heat
exchange medium passage that circulates the heat exchange medium
among the heat exchange device, the exothermic body, and the gas
absorbing device such that the heat exchange medium can exchange
heat with the heat exchange device, the exothermic body and the gas
absorbing device; and a gas detector configured and positioned at
at least one of the heat exchange device and the heat exchange
medium passage at a location to detect the specified gas that leaks
into the heat exchange medium.
15. A heat exchange system according to claim 14, wherein the gas
detector is located at a portion of the heat exchange device or the
heat exchange medium passage, which portion is higher in position
than the other portions thereof.
16. A heat exchange system according to claim 14, wherein the gas
detector is located at a portion of the heat exchange device or the
heat exchange medium passage, which portion has a larger volume
than the other portions thereof.
17. A heat exchange system according to claim 14, further
comprising a warning generator that generates a warning when the
gas detector detects leakage of the specified gas into the heat
exchange medium.
18. A heat exchange system according to claim 14, wherein the
specified gas comprises hydrogen, and wherein the gas detector
comprises a hydrogen detector.
19. A heat exchange system according to claim 14, wherein: the heat
exchange device comprises a radiator with a radiator cap located at
the top thereof; and the gas detector is attached to the radiator
cap.
20. A heat exchange system according to claim 14, wherein the
exothermic body comprises a fuel cell that receives the specified
gas and generates electric power.
21. A heat exchange system, comprising: an exothermic body capable
of generating heat, said exothermic body being supplied with a heat
exchange medium for heat exchange therewith; a gas absorbing device
comprising a gas absorbing alloy that is able to absorb or release
a specified gas; a heat exchange device configured and positioned
to perform heat exchange with the heat exchange medium; a heat
exchange medium passage that circulates the heat exchange medium
among the heat exchange device, the exothermic body, and the gas
absorbing device such that the heat exchange medium can exchange
heat with the heat exchange device, the exothermic body and the gas
absorbing device; a heat exchange medium storage device configured
and positioned to store at least an excess of the heat exchange
medium when the amount of the heat exchange medium that circulates
through the heat exchange system becomes excessive; and a gas
detector configured and positioned at at least one of the heat
exchange device, the heat exchange medium passage and the heat
exchange medium storage device at a location to detect the
specified gas that leaks into the heat exchange medium.
22. A heat exchange system according to claim 21, wherein: the heat
exchange medium storage device comprises a reserve tank; and the
gas detector is attached to an upper portion of the reserve
tank.
23. A heat exchange system according to claim 21, wherein the gas
detector is located at a portion of the heat exchange device or the
heat exchange medium passage or the heat exchange medium storage
device, which portion is higher in position than the other
portions.
24. A heat exchange system according to claim 21, wherein the gas
detector is located at a portion of the heat exchange device or the
heat exchange medium passage or the heat exchange medium storage
device, which portion has a larger volume than the other portions
thereof.
25. A heat exchange system according to claim 21, further
comprising a warning generator that generates a warning when the
gas detector detects leakage of the specified gas into the heat
exchange medium.
26. A heat exchange system according to claim 21, wherein the
specified gas comprises hydrogen, and wherein the gas detector
comprises a hydrogen detector.
27. A heat exchange system according to claim 21, wherein: the heat
exchange device comprises a radiator with a radiator cap located at
the top thereof; and the gas detector is attached to the radiator
cap.
28. A heat exchange system according to claim 21, wherein the
exothermic body comprises a fuel cell that receives the specified
gas and generates electric power.
29 (Cancelled)
Description
INCORPORATION BY REFERENCE
[0001] The disclosure of Japanese Patent Application No.
2000-060806 filed on Mar. 6, 2000 including the specification,
drawings and abstract, is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a heat exchange system which feeds
a heat exchange medium to a fuel cell so as to exchange heat with
the fuel cell, or which feeds a heat exchange medium warmed through
heat exchange with a heating element, to a gas absorbing device
such as a hydrogen gas absorbing alloy tank, so as to heat the gas
absorbing device.
[0004] 2. Description of Related Art
[0005] In general, a fuel cell generates power in the manner as
follows: hydrogen-containing fuel gas and oxygen-containing
oxidizing gas are supplied to a fuel cell, so that electrochemical
reactions take place at an anode and a cathode of the cell,
according to reaction formulas as indicated below.
[0006] To be more specific, when the fuel gas and the oxidizing gas
are supplied to the anode and the cathode, respectively, the
reactions as represented by formulas (1) and (2) take place at the
anode side and the cathode side, respectively, such that the fuel
cell as a whole undergoes a reaction as represented by formula
(3).
H.sub.2.fwdarw.2H.sup.++2e.sup.- (1)
2H.sup.++2e.sup.-+(1/2)O.sub.2.fwdarw.H.sub.2O (2)
H.sub.2+(1/2)O.sub.2.fwdarw.H.sub.2O (3)
[0007] Since these electrochemical reactions are heat generating or
exothermic reactions, the inside of the fuel cell must be cooled in
order to prevent the temperatures at the anode and the cathode from
rising excessively. To this end, a heat exchange system is usually
provided for feeding the fuel cell with cooling water as a heat
exchange medium cooled by a radiator, through a cooling water
passage, thereby to cool the inside of the fuel cell. One such type
of heat exchange system for a fuel cell is disclosed in Japanese
Patent Publication No. HEI 7-66828.
[0008] In some cases, the fuel gas to be fed to the fuel cell is
supplied from a hydrogen absorbing alloy tank containing a hydrogen
absorbing alloy. In general, hydrogen absorbing alloys have the
property of releasing hydrogen through an endothermic reaction when
heated, and of absorbing hydrogen through an exothermic reaction
when cooled. Therefore, in order to extract hydrogen from the
hydrogen absorbing alloy, the hydrogen absorbing alloy inside the
hydrogen absorbing alloy tank must be heated as needed. To this
end, the heat exchange system feeds the hydrogen absorbing alloy
tank with cooling water that is a heat exchange medium warmed by
heat exchange with a heating element such as a fuel cell, through a
cooling water passage, thereby to heat the inside of the hydrogen
absorbing alloy tank.
[0009] Thus, the heat exchange system feeds cooling water serving
as a heat exchange medium to the fuel cell in order to cool it and
to the hydrogen absorbing alloy tank in order to heat it.
[0010] In the fuel cell, the cooling water supplied to the cell is
completely separated from the fuel gas and the oxidizing gas by
separators in each single cell. When the fuel cell is used for an
extended period of time, however, the sealing member that seals the
periphery of each separator may deteriorate, causing the fuel gas
or oxidizing gas to leak into the cooling water.
[0011] In the hydrogen absorbing alloy tank, the supplied cooling
water runs through a tube while circulating within the tank, and is
thus completely separated from hydrogen gas (that is, fuel gas). In
some cases, the wall surface of the tube deteriorates after an
extended period of use, and the hydrogen gas leaks into the cooling
water.
[0012] In the conventional heat exchange system, however, no
countermeasure has been taken against leakage of the fuel gas or
oxidizing gas into the cooling water as the heat exchange medium.
Thus, the heat exchange system may suffer from deterioration of
heat exchange performance due to the presence of gas in the cooling
water.
SUMMARY OF THE INVENTION
[0013] It is an object of the invention to provide a heat exchange
system which can minimize the possibility of a specified gas
leaking into a heat exchange medium.
[0014] To accomplish at least a part of the above object, a heat
exchange system according to the first aspect of the invention
includes a fuel cell that receives a specified gas and generates
electric power, a heat exchange device that performs heat exchange
with a heat exchange medium, a heat exchange medium passage, and a
gas detector. The heat exchange medium passage circulates the heat
exchange medium between the heat exchange device and the fuel cell
such that the heat exchange medium can exchange heat with the heat
exchange device and the fuel cell. A gas detector is provided at at
least one of the heat exchange device and the heat exchange medium
passage at a location to detect the specified gas that leaks into
the heat exchange medium.
[0015] According to a second aspect of the invention, there is
provided a heat exchange system which includes an exothermic body
capable of generating heat, a gas absorbing device comprising a gas
absorbing alloy that is able to absorb or release a specified gas,
a heat exchange device configured and positioned to perform heat
exchange with a heat exchange medium, a heat exchange medium
passage and a gas detector. The heat exchange medium passage
circulates the heat exchange medium among the heat exchange device,
the exothermic body, and the gas absorbing device such that the
heat exchange medium can exchange heat with the heat exchange
device, the exothermic body and the gas absorbing device. The gas
detector is provided at at least one of the heat exchange device
and the heat exchange medium passage at a location to detect the
specified gas that leaks into the heat exchange medium.
[0016] In the heat exchange system of the invention as described
above, even where a specified gas leaks into the heat exchange
medium, the gas detector immediately detects leakage of the gas, of
which the driver can be promptly informed. Thus, the leakage of the
gas into the heat exchange medium will not be left as it is, and
otherwise possible deterioration of the heat exchange performance
due to bubbling of the specified gas can be advantageously
avoided.
[0017] The heat exchange system may further include a heat exchange
medium storage device for storing at least an excess of the heat
exchange medium when the amount of the heat exchange medium that
circulates through the heat exchange system becomes excessive. In
this case, the gas detector is provided at at least one of the heat
exchange device, the heat exchange medium passage and the heat
exchange medium storage device. The provision of the gas detector
at the heat exchange medium storage device also yields the same
advantage as described above.
[0018] Preferably, the gas detector is located at a portion of the
heat exchange device or the heat exchange medium passage, which
portion is higher in position than the other portions thereof or
has a larger volume than the other portions thereof.
[0019] Since gas is normally likely to collect at a location that
is higher in position or has a larger volume or capacity, the gas
detector is preferably disposed at such a location so that leakage
of the specified gas into the heat exchange medium can be more
quickly and surely detected.
[0020] In one preferred embodiment of the invention, the heat
exchange device comprises a radiator with a radiator cap located at
the top thereof, and the gas detector is attached to the radiator
cap.
[0021] In another preferred embodiment of the invention, the heat
exchange medium storage device comprises a reserve tank, and the
gas detector is attached to an upper portion of the reserve
tank.
[0022] Where the radiator is used as the heat exchange device, and
the reserve tank is used as the heat exchange medium storage
device, the gas detector is located at the upper portion of the
radiator or the reserve tank which is higher in position and has a
larger volume or capacity and at which the specified gas leaking
into the heat exchange medium is likely to collect. Also, the gas
detector provided at such a location can be relatively easily
detached or removed, thus facilitating maintenance or replacement
of the gas detector.
[0023] The heat exchange system of the invention is preferably
installed in a vehicle. In the case where a fuel cell and a
hydrogen absorbing alloy tank are installed in an electric vehicle
or a hybrid vehicle, for example, the heat exchange system
installed in the vehicle permits early detection of any leakage of
a specified gas into the heat exchange medium.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a schematic view showing a heat exchange system
according to a first embodiment of the invention;
[0025] FIGS. 2A and 2B are sectional views schematically showing a
stack structure and a single cell structure, respectively, of the
fuel cell of FIG. 1;
[0026] FIG. 3 is a schematic view showing a heat exchange system
according to a second embodiment of the invention; and
[0027] FIG. 4 is a view showing an example of another location at
which a hydrogen sensor may be installed.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0028] Hereinafter, presently preferred embodiments of the
invention will be described. FIG. 1 is a schematic view showing a
heat exchange system according to a first embodiment of the
invention.
[0029] The heat exchange system of this embodiment can cool a fuel
cell 30 and heat a hydrogen absorbing alloy tank 40. The heat
exchange system is installed in an electric vehicle or a hybrid
vehicle or the like having the fuel cell 30 and the hydrogen
absorbing alloy tank 40.
[0030] As shown in FIG. 1, the heat exchange system mainly includes
a radiator 10, cooling water passages 60 to 64, water pumps 70 and
76, valves 72 and 74, and a reserve tank 20, and uses cooling water
as a heat exchange medium flowing through the system. As the
cooling water, normal water can be used, but it is preferable to
use water to which anticorrosive and/or antifreeze treatment(s)
have been applied.
[0031] The radiator 10 is a heat exchange device for cooling the
cooling water warmed by the fuel cell 30, and includes an upper
tank 12 and a lower tank 14 for temporarily storing the cooling
water, and a core 16 for passing the cooling water. Although not
shown in FIG. 1, the core 16 is composed of a combination of narrow
water tubes through which the cooling water runs and wavy metal
plates called corrugated fins, the combination being in the form of
a network.
[0032] The cooling water warmed by the fuel cell 30 flows to the
upper tank 12 to be temporarily stored therein and then led to the
lower tank 14 through the water tubes in the core 16 to be stored
in the lower tank 14. While the cooling water passes through the
water tube, the fins that are in contact with the tubes take away
or dissipate the heat, to thus cool the cooling water. The fins are
cooled by the breeze while the vehicle is running, or by a cooling
fan (not shown) provided behind the radiator 10.
[0033] In this manner, the cooling water cooled and stored in the
lower tank 14 flows out from the lower tank 14 to reach the fuel
cell 30 through the cooling water passage 60. A water pump 70 is
provided midway in the cooling water passage 60 so as to forcibly
circulate the cooling water flowing through the cooling water
passage 60. The water pump 70 and another water pump 76 which will
be described later are both electrically driven.
[0034] The cooling water which has reached the fuel cell 30 enters
a manifold (not shown) that allows cooling water to flow into the
fuel cell 30, and is then divided into streams flowing into cooling
water channels within respective single cells so as to cool the
anode and cathode of each single cell. During the flow through the
fuel cell 30, the cooling water itself is warmed by taking heat
away from the anode and the cathode of each cell. The streams of
cooling water that have passed through these cooling water channels
again join together to reach a manifold (not shown) which allows
the cooling water to flow out from the fuel cell 30.
[0035] The cooling water that flows out from the fuel cell 30
passes through the cooling water passage 61 and is then divided
into two flow paths, one of which is led to a valve 72 and the
other of which is led to a valve 74. These valves 72 and 74
selectively switch between a flow path leading the cooling water
warmed by the fuel cell 30 to the hydrogen absorbing alloy tank 40
so as to heat the hydrogen absorbing alloy tank 40, and a flow path
bypassing the hydrogen absorbing alloy tank 40.
[0036] For example, when the valve 72 is closed and the valve 74 is
open, the warmed cooling water flows through the cooling water
passage 62 into the hydrogen absorbing alloy tank 40 so as to heat
the hydrogen absorbing alloy tank 40. On the contrary, when the
valve 72 is open and the valve 74 is closed, the warmed cooling
water bypasses the hydrogen absorbing alloy tank 40 without being
used to heat the hydrogen absorbing alloy tank 40.
[0037] The hydrogen absorbing alloy tank 40 contains a hydrogen
absorbing alloy 42. As is well known in the art, the hydrogen
absorbing alloy 42 has the property of releasing hydrogen through
an endothermic reaction when heated, and absorbing hydrogen through
an exothermic reaction when cooled. Therefore, when it is desired
to extract or take out absorbed hydrogen from the hydrogen
absorbing alloy tank 40, warmed cooling water is supplied to the
hydrogen absorbing alloy tank 40 so as to heat the hydrogen
absorbing alloy 42 in the hydrogen absorbing alloy tank 40 as
described above. On the other hand, when it is desired to store
hydrogen in the hydrogen absorbing alloy tank 40, the temperature
of the hydrogen absorbing alloy 42 in the tank 40 is lowered by
stopping the supply of the warmed cooling water to the hydrogen
absorbing alloy tank 40.
[0038] When the warmed cooling water is supplied to the hydrogen
absorbing alloy tank 40, the cooling water flows through a cooling
water tube 44 circulating within the hydrogen absorbing alloy tank
40 so as to heat the hydrogen absorbing alloy 42 in the hydrogen
absorbing alloy tank 40.
[0039] After flowing out from the hydrogen absorbing alloy tank 40,
the cooling water that heated the hydrogen absorbing alloy 42 is
returned to the upper tank 12 of the radiator 10 through cooling
water passages 63 and 64. Midway in the cooling water passage 63,
the water pump 76 is provided for forcibly circulating the cooling
water which has passed through the hydrogen absorbing alloy tank
40. Thus, the water pump 76 is driven when the valve 72 is closed
and the valve 74 is open.
[0040] When the cooling water is not supplied to the hydrogen
absorbing alloy tank 40, on the other hand, the warmed cooling
water that flows out from the fuel cell 30 is returned to the upper
tank 12 of the radiator 10 after passing through the valve 72 and
the cooling water passage 64.
[0041] A radiator cap 18, which also serves as a pressure
regulating valve, is mounted on the top of the upper tank 12, and a
cooling water tube 65 extends from the radiator cap 18 to a reserve
tank 20.
[0042] As shown in FIG. 1, the reserve tank 20 is a simple sealed
type reserve tank, and an air intake tube 66 connects to the
reserve tank 20 to maintain atmospheric pressure inside the reserve
tank 20.
[0043] When the temperature of the cooling water in the upper tank
12 rises to such an extent that part of the water boils and the
pressure within the upper tank 12 exceeds a predetermined level,
cooling water and steam emitted from the tank 12 are pushed out
through the cooling water tube 65 into the reserve tank 20. In the
reserve tank 20, the steam liquefies and returns to water 22
without being actively cooled because of the low ambient
temperature. Later, when the pressure inside the upper tank 12
becomes lower than the atmospheric pressure due to a decrease in
the temperature of the cooling water in the upper tank 12, the
cooling water flows out from the reserve tank 20 and runs back to
the upper tank 12 through the cooling water tube 65.
[0044] The reserve tank 20 has a cooling water supply cap 24
mounted atop it. The cooling water supply cap 24 can be opened so
that the cooling water 22 in the reserve tank 20 can be replenished
when it falls below a predetermined amount.
[0045] The heat exchange system shown in FIG. 1 has been
schematically described above. Hydrogen sensors 50 and 52 and so
forth, which are characteristic features of the invention, will be
described in detail later.
[0046] Next, a circulation path of fuel gas to be supplied from the
hydrogen absorbing alloy tank 40 to the fuel cell 30 will be
briefly described.
[0047] As shown in FIG. 1, a hydrogen gas is first supplied from
outside to the hydrogen absorbing alloy tank 40 through a hydrogen
gas inflow passage 80. At this time, if the supply of heated
cooling water to the hydrogen absorbing alloy tank 40 is stopped,
and the temperature of the hydrogen absorbing alloy tank 40 falls
as described above, the supplied hydrogen gas is absorbed in the
hydrogen absorbing alloy 42. Then, if the supply of the heated
cooling water to the hydrogen absorbing alloy tank 40 is started,
and the temperature inside the tank 40 rises, the hydrogen gas
absorbed in the hydrogen absorbing alloy 42 is released therefrom.
At this moment, a valve 82 is opened, and the released hydrogen gas
is supplied to the fuel cell 30 through fuel gas passages 81 and 83
to serve as fuel gas in the cell. Midway in the fuel gas passage 83
are provided a hydrogen gas compressor 84 for circulating the
hydrogen gas, a valve 85 for stopping the supply of the hydrogen
gas to the fuel cell 30, and a throttle valve 86 for adjusting the
amount of flow of the hydrogen gas to be supplied to the fuel cell
30. The hydrogen gas supplied to the fuel cell 30 enters a manifold
for fuel gas inflow and is then divided into streams flowing into
fuel gas channels within respective single cells so that the
hydrogen gas is supplied to the anode of each single cell, as will
be described later. The remaining hydrogen gas that was not
supplied to the anode is re-collected into a manifold for fuel gas
outflow and flows out from the fuel cell 30. The hydrogen gas thus
discharged is returned again to the fuel gas passage 81 through a
fuel gas passage 87 and circulated.
[0048] The schematic structure of the fuel cell 30 will be
described hereinafter with reference to FIGS. 2A and 2B. FIGS. 2A
and 2B are sectional views schematically showing stack structure
and single cell structure, respectively, of the fuel cell 30 as
shown in FIG. 1. FIG. 2A shows a section of the stack structure,
and FIG. 2B shows a section of the single cell structure which is
an enlargement of a portion of FIG. 2A including a single cell.
[0049] As shown in FIG. 2B, a single cell is composed of an
electrolyte film 35, an anode 36 and a cathode 37 which are
diffusion electrodes that sandwich the film 35 from both sides, and
two separators 34 which sandwich the electrodes from both sides.
The separators 34 have mutually opposed surfaces in which recesses
are formed, and cooperate with the anode 36 and cathode 37
sandwiched between the separators 34 to form gas channels within
the single cell. Of the gas channels thus formed, gas channels 32
formed between the separator 34 and the anode 36 allow hydrogen gas
supplied as described above as fuel gas to pass therethrough, and
gas channels 33 allow oxygen containing air, serving as oxidizing
gas, to pass therethrough.
[0050] In the present embodiment, as shown in FIG. 2A, two adjacent
separators 34, which are located at intervals of two single cells,
are in direct contact with each other, and have recesses formed in
their opposed surfaces such that cooling water channels 31 are
formed between the adjacent separators 34. The cooling water
supplied to the fuel cell 30 as described above is caused to flow
through the cooling water channels 31.
[0051] As shown in FIG. 2A, the cooling water flowing through the
cooling water channels 31 is usually completely separated from the
hydrogen gas and oxidizing gas respectively flowing through the gas
channels 32 and 33. However, as the fuel cell 30 is used for an
extended period of time, cracks may be formed in the separators 34,
or a sealing member (not shown) sealing the periphery of the
separators 34 may deteriorate, causing the hydrogen gas (and/or the
oxidizing gas) flowing through the gas channels 32 (and 33) to leak
into the cooling water flowing through the cooling water channels
31.
[0052] In the hydrogen absorbing alloy tank 40, the supplied
cooling water normally flows through the cooling water tube 44
circulating in the tank 40 while being completely separated from
the hydrogen gas, as shown in FIG. 1. In some cases, however, the
wall surface of the cooling water tube 44 may deteriorate after a
long period of use, and the hydrogen gas present in the upper
portion of the hydrogen absorbing alloy tank 40 may leak into the
cooling water passing through the cooling water tube 44.
[0053] If hydrogen gas leaks into the cooling water in the above
manner, the hydrogen gas turns into bubbles in the cooling water,
which may possibly result in deterioration of the heat exchange
performance of the entire heat exchange system.
[0054] In view of the above problem, the present embodiment adopts
the following structure for detecting leakage of hydrogen gas into
the cooling water early and informing the driver of the vehicle of
the gas leakage.
[0055] In the heat exchange system of the present embodiment as
shown in FIG. 1, the hydrogen sensor 50 is mounted in the radiator
cap 18 at the top of the radiator 10, and the hydrogen sensor 52 is
mounted at the top portion of the reserve tank 20. Each of the
hydrogen sensors 50 and 52 detects even a very small amount of
hydrogen if it is contained in the air, and outputs a detection
signal.
[0056] The heat exchange system of the present embodiment further
includes a control unit 90 and a hydrogen gas leakage warning lamp
92 provided on the dashboard of the driver's seat. The control unit
90 detects the leakage of hydrogen gas into the cooling water from
a detection signal received from the hydrogen sensors 50 and 52,
and outputs a driving signal. The hydrogen gas leakage warning lamp
92 lights up when the driving signal is received from the control
unit 90.
[0057] When hydrogen gas leaks into the cooling water, the hydrogen
gas turns into bubbles, which then flow through the cooling water
passage together with the cooling water and collect at a portion
within the heat exchange system which is higher in position and has
a relatively large capacity. To be more specific, the hydrogen gas
in the form of bubbles collects at the top portion of the upper
tank 12 of the radiator 10, or around the radiator cap 18, which is
located at the highest position in the heat exchange system. If the
pressure inside the upper tank 12 is high, the cooling water is
pushed out as described above from the upper tank 12 into the
reserve tank 20 through the cooling water tube 65 so that the
hydrogen gas caught within the upper tank 12 is also pushed out
into the reserve tank 20 along with the cooling water. The hydrogen
gas pushed out together with the cooling water turns into bubbles
in the cooling water 22 and floats up to the surface of the water,
to be present at the top of the reserve tank 20.
[0058] As described heretofore, the hydrogen sensors 50 and 52
mounted in the radiator cap 18 of the radiator 10 and in the
reserve tank 20, respectively, detect hydrogen gas collected at the
top of the upper tank 12 or at the top of the reserve tank 20 due
to the leakage of the hydrogen gas into the cooling water, and
output detection signals. Upon detecting the leakage of the
hydrogen gas into the cooling water from the detection signals, the
control unit 90 outputs a driving signal to the hydrogen gas
leakage warning lamp 92. The lamp 92 then lights up to inform the
driver that hydrogen gas is leaking into the cooling water.
[0059] Thus, in the heat exchange system of the present embodiment,
if hydrogen gas leaks into the cooling water, the hydrogen sensors
50 and 52 immediately detect the leakage, and the hydrogen gas
leakage warning lamp 92 informs the driver of the leakage. Once the
driver notices the lighting of the lamp 92, the driver can ask for
an inspection of the vehicle soon in order to get repairs or
replacements and so forth as necessary. The hydrogen gas collected
in the upper tank 12 of the radiator 10 and the hydrogen gas
collected at the top of the reserve tank 20 can be easily
discharged into the air by opening the radiator cap 18 and the
cooling water supply cap 24, respectively. Moreover, the hydrogen
sensors 50 and 52 are installed at sites which allow the sensors to
be comparatively easily detached, which facilitates the maintenance
or replacement of these hydrogen sensors.
[0060] FIG. 3 is a block diagram showing the structure of a heat
exchange system according to a second embodiment of the invention.
The heat exchange system of the present embodiment differs from the
system of the first embodiment shown in FIG. 1 in that a completely
sealed type reserve tank 100 is used instead of the simple sealed
type reserve tank 20. Since the other components are identical to
those shown in FIG. 1, the description of these components will be
omitted.
[0061] When the pressure in the upper tank 12 exceeds a
predetermined level due to a rise in the temperature of the cooling
water in the upper tank 12 of the radiator 10, the cooling water
and steam emitted from the tank 12 flow into the reserve tank 100
through a cooling water tube 68 in the same manner as with the
reserve tank 20 shown in FIG. 1. However, since the reserve tank
100 is of the completely sealed type unlike the reserve tank 20,
the cooling water never returns to the upper tank 12 from the
reserve tank 100 through the cooling water tube 68 even if the
pressure in the upper tank 12 falls due to a decrease in the
temperature of the cooling water in the upper tank 12. Instead, the
cooling water 22 in the reserve tank 100 is led to the cooling
water passage 60, not through the cooling water tube 68, but
through a cooling water passage 67 after leaving an outlet formed
at the bottom of the reserve tank 100.
[0062] Since hydrogen gas that leaks into the cooling water may
collect at the top of the reserve tank 100 in the present
embodiment, a hydrogen sensor 52 is provided at the top of the
reserve tank 100 for detecting the leakage of the hydrogen gas.
Thus, the present embodiment provides the same advantages as the
first embodiment. In addition, the use of the reserve tank of the
completely sealed type in the present embodiment eliminates a
possibility that impurities contained in the air may be introduced
into the cooling water.
[0063] While the hydrogen sensors are mounted in the radiator cap
18 of the radiator 10 and at the top of the reserve tank 20, 100 in
the illustrated embodiments, such a hydrogen sensor may be
installed midway in a cooling water passage connecting the radiator
10 and the fuel cell 30 or the hydrogen absorbing alloy tank 40 as
shown in FIG. 4.
[0064] FIG. 4 shows an example of a location at which a hydrogen
sensor may be installed. In FIG. 4, a portion of the cooling water
passage 64 through which the cooling water flows into the upper
tank 12 of the radiator 10 forms a circuit that projects upwards so
as to bypass an obstacle(s) or the like. Since the circuit portion
of the passage 64 is higher in position than the other portions, it
is considered that hydrogen gas that leaks into the cooling water
and turns into bubbles is likely to collect at the circuit portion.
In this modified example, therefore, another hydrogen sensor 54 is
provided at the circuit portion of the cooling water passage
64.
[0065] Thus, the same advantages as provided in the illustrated
embodiments may be obtained by providing an additional hydrogen
sensor at a portion of the cooling water passage which is higher in
position than the other portions.
[0066] It is to be understood that the invention is not limited to
details of the illustrated embodiments, but may be embodied with
various changes or improvements without departing from the scope of
the invention.
[0067] In the heat exchange system of each of the above
embodiments, the fuel cell 30 is cooled by using the cooling water,
and the hydrogen absorbing alloy tank 40 is heated by using the
cooling water that has been warmed through the cooling of the fuel
cell 30. However, the invention is not restricted to this type of
system. For instance, the invention is applicable to a system in
which cooling water is used only to cool the fuel cell 30. In
another example of the heat exchange system, the hydrogen absorbing
alloy tank 40 can be heated by cooling water that has been warmed
not by taking heat away from the fuel cell 30 but by cooling
another heat-generating or exothermic body (auxiliary equipment or
an engine in the case of a hybrid car, for example).
[0068] In the illustrated embodiments, the hydrogen sensors 50, 52,
and 54 detect the presence of hydrogen in the air. However, if a
sensor capable of detecting the presence of hydrogen in a liquid is
developed, such a sensor could also be used. In that case, sensors
could be installed at any location in the path through which the
cooling water flows, without taking account of the height in
position or the likelihood of collection of hydrogen gas in the
form of bubbles.
[0069] While leakage of hydrogen gas into cooling water is detected
by the hydrogen sensors in the illustrated embodiments, leakage of,
for example, oxidizing gas into cooling water may be detected by
using a gas sensor for detecting oxidizing gas.
[0070] In the illustrated embodiments, cooling water is used as a
heat exchange medium. However, the invention is not restricted to
this, but may use a heat exchange medium other than water.
[0071] In the above embodiments, the warning lamp 92 is used to
visually inform the driver that hydrogen gas is leaking into the
cooling water. Alternatively, a beeper or a speaker can be used to
give notification by sound.
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