Chemistry: electrical current producing apparatus – product – and – With pressure equalizing means for liquid immersion operation
Reexamination Certificate
2000-11-16
2003-03-25
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
With pressure equalizing means for liquid immersion operation
C429S010000, C429S006000, C429S006000
Reexamination Certificate
active
06537692
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell apparatus, and in particular, to an improvement of a so-called PEM type fuel cell apparatus having a polymer solid electrolyte film. More particularly, the present invention relates to an improvement of a water direct injection type, in particular, to a fuel cell apparatus with direct spraying of water onto an air electrode from a nozzle.
A cell main body of the PEM type fuel cell apparatus has a structure including a polymer solid electrolyte film held between a fuel electrode (also called as a hydrogen electrode in the case of using hydrogen as a fuel electrode) and an air electrode (also called an “oxygen electrode” or “oxidation electrode” because oxygen is a reaction gas. A reaction layer including a catalyst is interposed between the air electrode and the electrolyte film.
The fuel cell having the above structure is generated in an electromotive force in the following manner. More specifically, a fuel gas is supplied to a fuel electrode side (anode), and then, an oxidation gas is supplied to an air electrode side; as a result, electricity is generated with the progress of electrochemical reaction, and then, the electrocity thus generated is picked up by an external circuit.
More specifically, a hydrogen ion obtained by the fuel electrode (anode) is moved in the form of a ion (H
3
O
+
) to the air electrode (cathode) side in an electrolyte film containing water. Moreover, an electron obtained by the fuel electrode (anode) is moved to the air electrode (cathode) side through an external load, and then reacts with oxygen contained in an oxidation gas (e.g., air) to generate water. Thus, electric energy generated by consecutive electrochemical reactions.
The present applicant previously proposed a fuel cell apparatus in Japanese Application No. 10-378161. The fuel cell apparatus has a structure supplying liquid water onto the surface of air electrode for the purpose of cooling the air electrode having an exothermic reaction so as to improve power generation performance.
In a so-called water direct injection type fuel cell apparatus as proposed in the above application, feed water is controlled in accordance with temperature of the fuel cell main body so as to cool the fuel cell main body. On the other hand, a predetermined amount of process air is constantly supplied to the air electrode. In other words, the air volume delivered by the air supply system is always constant. Applicants' prior application describe influence of the sensible heat and latent heat of the water cooling the fuel cell main body. In this case, the sensible heat is that heat which is removed from the fuel cell main body without vaporization of the supplied water. On the other hand, the latent heat is heat which is removed from the fuel cell main body by vaporization of the directly injected water.
It has now been found that the latent heat of water is used to cool the fuel cell main body, and that the sensible heat makes little contribution to cooling. Therefore, in order to more effectively use the latent heat of water, in other words, in order to more effectively cool by vaporizing water supplied to the air electrode, supply amount of process air supplied to the air electrode, that is, the air volumetric flow rate should be controlled. Given, such insight applicants now recognize a number of deficiencies in the previously proposed water direct injection type fuel cell apparatus.
More specifically, when the fuel cell main body is operated at a high temperature, unless the amount of air (predetermined amount of supply) supplied to the air electrode is sufficient to properly utilize the latent heat of water, the fuel cell dries up and for this reason, the air temperature becomes high. In such a case, in order to cool the fuel cell main body, a large amount of water is supplied so as to utilize the latent heat of vaporization of water. However, in this case, a large capacity pump is required for supplying the large amount of water. The large capacity pump hinders any attempt to miniaturize the fuel cell apparatus, and a great amount of power is consumed in driving the large capacity pump, thus reducing the efficiency of the fuel cell apparatus. Moreover, when a large amount of water is supplied to the fuel cell, its process air passage fills with water, or a water membrane is formed on the surface of the air electrode, creating the possibility that the amount of oxygen necessary for the chemical reaction of the fuel cell will not be supplied to the air electrode.
On the other hand, when the fuel cell main body is operated at a low temperature, in the case where the air (predetermined amount) supplied to the air electrode is excessive, the temperature of the fuel cell main body is lowered, and there is a power loss for the fan which supplies the air.
The water evaporated at the air electrode is condensed for recycle by a condenser together with reaction water and, thereafter, is recovered. The condenser can effectively condense water when only a small amount of air is to be treated and the temperature of the air is high, in which case the capacity of the condenser can be small and the condenser small is size. In the case where the fuel cell main body is operated at a low temperature and the supply of process air is larger, a larger capacity (large size) condenser is required.
SUMMARY OF THE INVENTION
The present invention has been made taking the above-described problem in the prior art into consideration. It is, therefore, an object of the present invention to provide a fuel cell apparatus, which includes a water supply for supplying water, in liquid form, onto a surface of an air electrode of a fuel cell.
The fuel cell apparatus of the present invention further includes an air supply controller for varying the amount of process air supplied to the air electrode.
In the fuel cell apparatus constructed as described above, the amount of process air (volumetric flow rate) is variable so that it can be set to the optimum amount, whereby it is possible to sufficiently and effectively cool using the latent heat of evaporation of water supplied to the air electrode, i.e., to effectively cool the air electrode, in particular, and the fuel cell body, in general. The droplet size of the water spray ranges from 50 &mgr;m to 500 &mgr;m in order to most effectively use latent heat of evaporation of the water. Moreover, it is desirable that the thickness of the electrolyte film of the fuel cell be less than 200 &mgr;m.
More specifically, when the fuel cell main body is operated at a high temperature to reduce the temperature, the amount of air supplied per unit time, (the amount of air passing through the air chamber A—see
FIG. 3
) is increased, taking caution that a sufficient amount of water is supplied. In prior art apparatus wherein the supply of air is fixed the sensible heat of water is used, and a relatively large quantity of water must be supplied and for this reason, there are various problems even if the amount of air supplied is increased. In the present invention, however, almost no problem is caused even if the amount of air supplied is great. Even then, the load on the air supply device (fan, etc.) is extremely small as compared with the prior art which uses a greater amount of water.
When the fuel cell is operated at a low temperature to increase its operating temperature, the amount of the air supply is decreased. By doing so, it is possible to securely increase the temperature of the fuel cell main body, while reducing the power consumed by the air supply device to the extent possible.
Moreover, in the water recycle condenser, as the internal air temperature increases, the temperature difference between the internal and external air increases and, therefore, the capacity of the condenser can be made smaller.
According to the present invention, the air supply and the water supply are controlled independently of each other. Therefore, it is possible to independently control the required amounts of the air and water with
Horiguchi Munehisa
Kato Kenji
Kabushikikaisha Equos Research
Kalafut Stephen
Lorusso & Loud
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