JPH0799698B2 - Fuel cell temperature controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a temperature adjusting device capable of smoothly increasing the temperature inside a cell during a starting operation of a fuel cell.

[Conventional technology]

A fuel cell is formed by stacking a plurality of unit cells consisting of a matrix impregnated with an electrolyte solution and a pair of fuel electrodes sandwiching the matrix and an oxidizer electrode to form a stack. Electricity is generated by supplying air with an electrochemical reaction.

When the fuel cell supplies a current to the load, the internal voltage of the fuel cell, the diffusion resistance of the fuel gas and the oxidant gas to the electrode, and the energy loss due to the electrode reaction increase as the current increases, and the output voltage gradually decreases. The energy loss corresponding to the voltage drop is released as heat. The electrode reaction of the fuel cell is an exothermic reaction, and heat is generated almost in proportion to the electric current. In addition, the voltage drop caused by the deterioration of the electrode characteristics also causes an increase in heat.

On the other hand, the fuel cell has an appropriate operating temperature for high efficiency operation. For example, the phosphoric acid fuel cell has an appropriate operating temperature of 190 to 195 ° C. To maintain this proper operating temperature, the self-heating of the fuel cell that accompanies power generation after the start of operation of the fuel cell is used, but as mentioned above, an increase in current may cause an excessive temperature rise. In order to suppress it, as shown in the system diagram of FIG. 3, a cooling system for the heat medium that passes through the heat exchanger in the fuel cell main body and circulates outside is provided.

The conventional cooling system and temperature raising system will be described below with reference to FIG. 3. The fuel cell 1 is provided with a heat medium circulation path 2 connected by piping. This circulation path 2 has a circulation pump 3,
The heat exchanger 9, the heat medium tank 5, and the heat exchanger in the fuel cell 17 are connected by piping, and the heat generated in the fuel cell 1 is radiated to the outside by the heat medium. Water or cooling oil is used as the heat medium, but here, the case where cooling oil is used is targeted. As a cooling oil, heat resistance,
From the viewpoint of flame retardancy and harmless to the human body, heat resistant and flame retardant oils such as dibenzine / toluene and silicone oil are used. Further, a temperature sensor 7 is provided in the fuel cell 1 to monitor its operating temperature, and a fan 8 is rotated to circulate the heat medium when a strong cooling is required by a signal from the controller 15 according to the temperature condition. When the fuel cell is started or when the temperature is lower than the reference value, the temperature raising burner 4 is operated,
The fan 8 is rotated, and the heat medium is heated by the heat exchanger 9 and sent to the fuel cell 1, and is controlled so that the operating temperature is maintained appropriately.

An exhaust port having a valve 13 is attached to the heat medium tank 5 so that the heat medium tank 5 can be exhausted when the pressure inside the tank rises.

[Problems to be Solved by the Invention]

By the way, a fuel cell provided with a cooling system and a temperature raising system as described above is used in the heat medium circulation path in a cold region in winter, when the ambient temperature may require a start operation from below freezing. As a heat medium consisting of heat-resistant and flame-retardant oil, for example, using dibenzyl toluene,
As shown in the characteristic diagram of viscosity and temperature in FIG. 4, the viscosity of the heat medium sharply increases as the temperature decreases, so that the driving power of the circulation pump 3 increases and the pipe size of the heat medium circulation passage 2 increases. In addition, an increase in temperature, a temperature raising device such as an electric heater for preheating the heat medium tank 5, the heat medium tank 5 and the heat medium pipe, and a power source thereof are required. For this reason, the fuel cell power generator becomes large in size, and the loss of auxiliary machinery also increases, which is a factor to prevent the size and weight reduction of a fuel cell used for applications such as a mobile power source.

In view of this point, the present invention provides a fuel cell that exhibits a sufficient temperature raising capability even when starting operation in an extremely low ambient temperature, and that does not interfere with temperature adjustment with good responsiveness during normal operation. An object of the present invention is to provide a temperature control device.

[Means for Solving the Problems]

In order to solve the above problems, according to the present invention, a first heat exchanger provided in a fuel cell, a heat medium tank,
In a temperature control device for a fuel cell, which includes a heat medium circulation path for sequentially connecting a circulation pump and a second heat exchanger including a burner and a fan, and circulating a heat medium composed of heat-resistant and flame-retardant oil, Valves are provided between the first heat exchanger and the heat medium tank and between the second heat exchanger and the first heat exchanger, respectively, and the second heat exchanger side of the two valves is provided. In the heat medium circulation path, a heat medium bypass path connected via a valve is provided between the heat medium tank and the second heat exchanger outlet, and the first heat exchanger and the second heat exchanger are provided. It is assumed that a heat medium purging gas supply source is connected via a valve in the vicinity of the valve provided between the first heat exchanger and the valve provided between the heat exchanger and the first heat exchanger.

[Action]

According to the configuration of the present invention, in the winter cold region, when the fuel cell is started, the heat medium bypass is connected to the heat medium circulation passage connected to the heat exchanger in the fuel cell, which adjusts the temperature of the fuel cell conventionally provided. Since the passage is provided, the heat medium heated by the second heat exchanger, the burner and the fan provided therein, passes through the heat medium bypass passage by the operation of the valve, enters the heat medium supply source, and circulates. Second by pump again
Sent to the heat exchanger of. This circulation rapidly raises the temperature of the heat medium, and when the temperature reaches the reference value, the heat medium bypass passage is closed by operating the valve to supply the heat medium to the first heat exchanger in the fuel cell, and the operating temperature of the fuel cell is increased. Contribute to the temperature rise up to.

If the heat medium that had become highly viscous due to cooling due to the ambient temperature during the stoppage remained in the piping of the heat exchanger in the fuel cell,
When the above-mentioned sufficiently viscous low-viscosity heat medium is supplied at the time of start-up, the increase in the resistance in the pipe will be an obstacle to its operation due to the high-viscosity heat medium, so when the fuel cell is stopped, at the time of the next restart. Therefore, while the heat medium has a high temperature and low viscosity, the heat medium purging gas is supplied to the heat medium circulation passage through the valve, and the heat medium is returned to the heat medium tank by the pressure of the gas. Thus, according to the present invention, by providing the heat medium bypass passage and the heat medium purging gas supply source, the fuel cell can be easily started even in a cold region.

〔Example〕

The present invention will be described below based on examples. FIG. 1 is a system diagram showing an embodiment of the present invention. The same parts as those in FIG. In FIG. 1, a valve 31 and a valve 33 are provided in the heat medium circulation passage 2, and a heat medium bypass passage 12 is provided through the valve 32 toward the heat medium tank 5 through the pipe between the valve 31 and the heat exchanger 9. Has been.

In order to start the fuel cell from a low ambient temperature in cold regions, first, the valves 31 and 33 are closed, the valve 32 is opened, and the circulation pump 3 and the burner 4 are operated. By doing so, the heat medium which is left at a low temperature and has a high viscosity is circulated and heated in the bypass passage 12 having a short pipe length without passing through the heat exchanger 17 in the fuel cell. Next, when the temperature detected by the heat medium temperature sensor 6 attached to the heat medium tank 5 reaches the reference value, the valve 32 is closed and the valves 31 and 33 are opened by the command of the control unit 16, and the heat exchanger in the fuel cell is opened. The heat medium is supplied to 17 and the temperature is continuously raised until the fuel cell reaches the operating temperature.

When the fuel cell stops operating, the valves 31 and 32 are closed and the valves 33 and 34 are opened while the temperature of the heat medium is high so that the fuel cell can be started quickly without trouble during the next restart. The purging gas is supplied from the gas tank as the medium purging gas supply source to the heat medium circulation passage 2 through the pressure reducing valve 35, and the high temperature heat medium in the pipe and in the heat exchanger 17 in the fuel cell is purged by the gas. It is returned to the heat medium tank 5 under the pressure of. By doing so, the temperature of the heat medium becomes low at a low ambient temperature during operation stop, the viscosity becomes high, and the obstacle caused by the increase in resistance in the pipe at the next restart can be removed. The first
In the figure, the position of the circulation pump 3 is not limited to the above-described embodiment, but is located in the heat medium circulation passage between the heat medium outlet side of the second heat exchanger and the heat medium bypass passage inlet. You may.

FIG. 2 is a system diagram showing a different embodiment of the present invention. The difference from the embodiment shown in FIG. 1 is that a heat medium purging compressor is provided in place of the heat medium purging gas tank so that air can be purged by the gas. Used as the first
The device can be downsized as compared to the embodiment shown in the figure.

〔The invention's effect〕

As described above, the present invention sequentially connects the first heat exchanger provided in the fuel cell, the heat medium tank, the circulation pump, the second heat exchanger having the burner and the fan, as described above,
In a temperature control device for a fuel cell, comprising a heat medium circulation path for circulating a heat medium composed of heat resistant / flame retardant oil, between the first heat exchanger and the heat medium tank, and the second heat exchanger. And a valve between the first heat exchanger and
In the heat medium circulation path on the second heat exchanger side of the two valves, a heat medium bypass path connected via a valve is provided between the heat medium tank and the second heat exchanger outlet, Gas supply source for heat medium purging via a valve in the vicinity of the valve between the valve provided between the first heat exchanger and the second heat exchanger and the first heat exchanger Since it is connected to the fuel cell, when the fuel cell is started from the ambient temperature below freezing in cold regions in winter, it is possible to avoid the use of the heat medium at low temperature and high viscosity. As a result, the piping size of the heat medium circulation path can be reduced. Also, the power of the circulation pump that drives the circulation of the heat medium can be kept low. Further, conventionally, the piping of the equipment for cold regions has used the electric heating function for heat retention and preheating, but this is no longer necessary, and the electric heating device and the power source are not required, and the fuel cell power generator can be made compact and lightweight.

[Brief description of drawings]

1 is a system diagram showing an embodiment of the present invention, FIG. 2 is a system diagram showing a different embodiment of the present invention, FIG. 3 is a system diagram showing a conventional example, and FIG. 4 is a temperature and viscosity of a heat medium. It is a graph which shows the relationship of. 1: Fuel cell, 2: Heat medium circulation path, 3: Circulation pump, 4: Burner, 5: Heat medium tank, 6: Heat medium temperature sensor, 7: Fuel cell temperature sensor, 8: Fan, 9: Heat exchanger , 10: Heat medium purging gas tank, 11: Heat medium purging compressor, 12: Heat medium bypass passage, 13, 31, 32, 33, 34: Valve, 15, 16: Control section, 1
7: Fuel cell heat exchanger, 35: Pressure reducing valve.

Claims (1)

[Claims] 1. A first heat exchanger provided in a fuel cell, a heat medium tank, a circulation pump, and a second heat exchanger equipped with a burner and a fan are sequentially connected to each other, so that heat resistance and difficulty can be improved. In a temperature control device for a fuel cell, which comprises a heat medium circulation path for circulating a heat medium made of a combustible oil, there is provided between the first heat exchanger and a heat medium tank, and between the second heat exchanger and the first heat exchanger. And a valve between the heat medium tank and the outlet of the second heat exchanger in the heat medium circulation path of the two valves on the second heat exchanger side. A heat medium bypass passage connected through the valve, and a valve provided between the first heat exchanger and the second heat exchanger and the valve between the first heat exchanger. A temperature control device for a fuel cell, characterized in that a heat medium purging gas supply source is connected in the vicinity through a valve.