Heat exchange system

Details Heat exchange system Heat exchange system

2001-03-05

2004-10-05

Chaney, Carol (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

With pressure equalizing means for liquid immersion operation

C180S065100, C180S065310

Reexamination Certificate

active

06800389

ABSTRACT:

INCORPORATION BY REFERENCE
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
1. Field of the Invention
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.
2. Description of Related Art
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.
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
2
→2H
+
+2e
−
  (1)
2H
+
+2e
−
+(½)O
2
→H
2
O  (2)
 H
2
+(½)O
2
→H
2
O  (3)
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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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, t

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