JP2005158510A - Heat exchanger for fuel cell vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat exchanger for a fuel cell vehicle capable of preventing accumulation of bubbles in a liquid passage. <P>SOLUTION: This heat exchanger is equipped with: a gas passage 51 for gas to flow; the liquid passage 52 disposed so that a flowing liquid thermally contacts the gas passage 51. The liquid passage 52 is disposed by nearly vertically directing it, and the liquid is led out from the upper end 44 of the liquid passage 52. Therefore, the liquid flowing through the inside of the liquid passage 52 flows from the nearly vertical lower side to the upper side. Therefore, bubbles mixed into the liquid passage 52 and bubbles generated by heating of the liquid passage 52 are raised from the lower side to the upper side along the flow of the liquid, and led out from the upper end 44 of the liquid passage 52 as it is. As a result, the accumulation of the bubbles in the liquid passage 52 can be prevented, and heat exchange performance degradation and thermal stress generation caused by the accumulation of the bubbles in the liquid passage 52 can be prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat exchanger for a fuel cell vehicle used in a fuel cell system as a vehicle drive source.

  The fuel cell system is a fuel cell, and is provided on both sides of the electrolyte by electrochemically reacting a fuel gas such as hydrogen gas (anode supply gas) and an oxidizing gas containing oxygen (cathode supply gas) via an electrolyte. Electric energy is directly taken out between the electrodes.

In recent years, fuel cell vehicles equipped with this fuel cell system as a vehicle drive source have been put into practical use. In this fuel cell vehicle, many heat exchangers are used. For example, there is a heat exchanger as disclosed in Patent Document 1.
JP 06-034295 A

  However, in the heat exchanger for a fuel cell vehicle disclosed in Patent Document 1, since the tube through which the liquid is circulated is arranged in the horizontal direction, bubbles are mixed in the liquid flow path formed in the tube. In this case, bubbles tend to accumulate in the liquid flow path. The part where the bubbles are accumulated becomes a part where heat exchange between the hot gas and the liquid is not effectively performed. In addition, since a temperature difference occurs between the part where the bubbles are accumulated and other parts, a thermal stress larger than usual may be generated in the heat exchanger due to the temperature difference.

  In particular, in a heat exchanger in which the combustion gas of the combustor is ventilated to exchange heat between the high-temperature combustion gas and the liquid, many bubbles are likely to be generated due to boiling of the liquid.

  Accordingly, an object of the present invention relates to a heat exchanger for a fuel cell vehicle capable of preventing bubbles from staying in a liquid flow path in order to solve the above-described conventional problems.

  A heat exchanger for a fuel cell vehicle according to the present invention includes a gas flow path through which a gas flows, and a liquid flow path that is disposed so as to be in thermal contact with the gas flow path and through which the liquid flows. The gist of the invention is that the liquid flow path is arranged in a substantially vertical direction and the liquid is led out from the upper end of the liquid flow path.

  According to the present invention, the liquid flowing through the liquid channel flows from the lower side to the upper side in the substantially vertical direction. For this reason, the bubbles mixed in the liquid flow path rise upward from below along the flow of the liquid and are led out from the upper end of the liquid flow path as they are.

As a result, bubbles can be prevented from staying in the liquid flow path. As a result, it is possible to prevent deterioration in heat exchange performance and generation of thermal stress caused by retention of bubbles in the liquid flow path.

  Hereinafter, an embodiment of a heat exchanger for a fuel cell vehicle according to the present invention will be described in detail with reference to the drawings.

"Overall configuration of fuel cell system"
First, a fuel cell system as a drive source for a fuel cell vehicle in which the heat exchanger 8 of this embodiment is interposed will be described. FIG. 1 is a conceptual diagram of the fuel cell system, and FIG. 2 is a plan view of the vicinity of the combustor and heat exchanger 8 of the fuel cell system.

  As shown in FIG. 1, the fuel cell system includes a hydrogen supply device (fuel gas supply device) 1 that supplies hydrogen as a fuel gas via a hydrogen supply pipe 11, and an oxidant gas via an air supply pipe 14. An air supply device (oxidant gas supply device) 2 for supplying air, an anode (fuel electrode) 4 and a cathode (oxidant electrode) 5 as electrodes, and hydrogen and oxygen supplied to each electrode are used. A fuel cell 3 for generating electricity, an anode offgas circulation device 6 for circulating the anode offgas upstream of the anode 4 via the anode offgas circulation pipe 12, a combustor 7 for combusting the anode offgas, and a refrigerant in the combustion exhaust gas of the combustor 7 A heat exchanger 8 for heating the air, a cooling device 9, a humidifier 10A for humidifying hydrogen as an anode supply gas, and a humidification for humidifying air as a cathode supply gas 10B, the air flow control valve 16, the heat exchanger 8 or the refrigerant pump 21 for circulating the refrigerant in the refrigerant flow path 20 between the cooling device 9 and the fuel cell 3, and the refrigerant flow path 20 through the heat exchanger 8 or A three-way valve 22 for switching to the cooling device 9, an anode offgas discharge valve 27 for discharging the anode offgas from the anode offgas circulation device 6 to the combustor 7 via the anode offgas discharge pipe 13, and a system controller 37 for controlling the entire fuel cell system. And.

  In this embodiment, the anode supply gas humidifier 10A and the cathode supply humidifier 10B have different configurations. The humidifier 10 </ b> A for anode supply gas humidifies hydrogen flowing through the hydrogen supply pipe 11 using water stored in the water tank 25. On the other hand, the humidifier 10B for the cathode supply gas has an assembly of hollow fiber membranes inside, and distributes the cathode off gas inside the hollow fiber membrane and distributes the cathode supply gas outside the hollow fiber membrane. The cathode supply gas is humidified with moisture in the off gas. That is, the cathode supply humidifier 10B is a water recovery device that recovers the moisture of the cathode offgas.

"Operation of the fuel cell system"
Next, the operation of the fuel cell system will be described.

  First, hydrogen from the hydrogen supply device 1 is humidified by the humidifier 10A and supplied to the anode 4, and air from the air supply device 2 is humidified by the humidifier 10B and supplied to the cathode 5, and these hydrogen and air are supplied. The fuel cell 3 reacts to generate electricity. At that time, the anode 4 which is not consumed and is left out is discharged from the anode 4. Also, a part of oxygen is consumed from the cathode 5 and cathode off gas containing moisture generated by power generation is discharged.

  During normal operation, the anode off-gas is circulated through the anode off-gas circulation pipe 6 through the anode off-gas circulation pipe 12 to the hydrogen supply pipe 11 and supplied to the anode 4 again. On the other hand, the cathode off gas is exhausted out of the system through the humidifier 10B, the combustor 7, the heat exchanger 8, and the exhaust pipe 19.

  Here, when a voltage lower than a predetermined voltage value is detected by the voltage detection means for detecting the cell voltage of the fuel cell 3, the system controller 37 determines that the amount of impurities accumulated in the anode supply gas has increased. The purge signal is transmitted to the combustor 7 based on the anode offgas discharge valve 27 based on the purge signal.

  In the combustor 7, the anode offgas (exhaust hydrogen) supplied via the anode offgas discharge valve 27 is mixed with the cathode offgas by the mixer 23, and this mixed gas is combusted in the combustion chamber 24 having a combustion catalyst. The combustion gas generated in the combustor 7 passes through the heat exchanger 8 and is exhausted outside the system (atmosphere) through the exhaust pipe 19.

  The combustor 7 can be supplied with hydrogen from the hydrogen supply device 1 through a pipe (not shown) and can be supplied with air through a pipe (not shown) to process the purged exhausted hydrogen. In addition to the time, heat can be generated by burning hydrogen and air (oxygen). Using this combustion heat, the fuel cell 3 can be heated as required.

"Fuel cell temperature control"
Next, temperature management of the fuel cell 3 will be described. The temperature of the fuel cell 3 is controlled so that the operating temperature is maintained at an appropriate temperature by a refrigerant such as antifreeze.

  During normal operation of the fuel cell system, it is necessary to keep the heated fuel cell 3 cooled to an appropriate operating temperature. Therefore, by connecting the refrigerant pump 21 and the cooling device 9 with the three-way valve 22, the refrigerant is circulated in a closed circuit of the refrigerant pump 21, the three-way valve 22, the cooling device 9, the fuel cell 3, and the refrigerant pump 21. Yes. As a result, the heat generated by the fuel cell 3 is released from the cooling device 9 to the outside of the system, and the temperature of the fuel cell 3 is maintained at an appropriate temperature.

  On the other hand, when starting the fuel cell system, it is necessary to raise the fuel cell 3 to an appropriate operating temperature. Therefore, the refrigerant pump 21 and the heat exchanger 8 are communicated with each other by the three-way valve 22 so that the refrigerant is circulated in the closed circuit of the refrigerant pump 21, the three-way valve 22, the heat exchanger 8, the fuel cell 3, and the refrigerant pump 21. It has become. As a result, the medium used as the refrigerant during normal operation can be used as the heating medium, and the temperature of the fuel cell 3 can be increased to an appropriate temperature for starting operation by raising the temperature of the heating medium with the heat exchanger 8. .

"Heat exchanger"
Next, a heat exchanger used in the fuel cell system will be described. 3 is a plan view of an assembly body in which a combustor, a heat exchanger, and an exhaust pipe are assembled. FIG. 4 is a side view of the assembly body. FIG. 5 is a vertical sectional view schematically showing the heat exchanger of this embodiment. is there.

  As shown in FIGS. 3 and 4, the heat exchanger 8 is housed in a cylindrical casing 62 inside a cylindrical heat shield 61. A combustion gas inlet 63 connected to the exhaust port of the combustor 7 is provided at one open end of the casing 62, and a combustion gas outlet 64 connected to the exhaust pipe 19 inlet at the other open end of the casing 62. Is provided.

  As shown in FIG. 5, the heat exchanger 8 is formed by alternately laminating flat tubes 42 and corrugated outer fins 43, and a reinforcing side plate 48 is attached to the outermost side in the laminating direction of the flat tubes 42. Has been.

  The flat tube 42 is arranged in the vertical direction. A cylindrical tank forming portion 42b that protrudes in the stacking direction Z of the flat tubes 42 is provided at the upper end and the lower end of each flat tube 42, and the cylindrical tank forming portions of the adjacent flat tubes 42 are provided. 42b communicates with each other. Thereby, an upper tank 44 is formed at the upper end of the heat exchanger 8, while a lower tank 45 is formed at the lower end of the heat exchanger 8.

  By being configured in this way, a gas flow path 51 through which combustion gas flows is formed between the flat tubes 42, and there is liquid inside the tube main body portion 42 a between the upper end portion and the lower end portion of the flat tube 42. A liquid channel 52 through which the water flows is formed. The liquid flowing in the liquid flow path 52 is in thermal contact with the gas flowing in the gas flow path 51 through the material of the flat tube 42. In the flat tube 42, a wavy inner fin (not shown) is interposed.

  In this embodiment, a pipe 47 as a heat exchanger liquid inlet is connected to one end of the lower tank 45 in the longitudinal direction, and a pipe as a heat exchanger liquid outlet is connected to one end of the upper tank 44 in the longitudinal direction. 46 is connected. Both the pipe 47 as the heat exchanger inlet and the pipe 46 as the heat exchanger liquid outlet are provided on one side (right side in FIG. 5) of the flat tubes 42 in the stacking direction Z.

  In the heat exchanger 8 configured as described above, the liquid flows as indicated by arrows in FIG. That is, the liquid supplied to the lower tank 45 through the pipe 47 as the heat exchanger liquid inlet flows from the lower side to the upper side of the liquid flow path 52 in each flat tube 42, and then is collected in the upper tank 44. It is discharged through a pipe 46 as a heat exchanger liquid outlet. The liquid is heated by the high-temperature combustion gas flowing through the gas flow path 51 between the flat tubes 42 when flowing through the liquid flow path 52 in the flat tube 42, and the heated liquid is taken out of the heat exchanger 8. It is. As a result, the combustion gas directed from the combustor 7 to the exhaust pipe 19 via the heat exchanger 8 is cooled by the heat exchanger 8 and exhausted through the exhaust pipe 19 (see FIGS. 3 and 4).

"effect"
Such a heat exchanger 8 has the following effects.

  First, according to the heat exchanger 8 of this embodiment, the gas flow path 51 through which the gas flows and the liquid flow path 52 arranged so that the flowing liquid is in thermal contact with the gas flow path 51. And the liquid channel 52 is arranged in a substantially vertical direction and the liquid is led out from the upper end portion 44 of the liquid channel 52. It circulates from the lower side to the upper side in the substantially vertical direction.

  Therefore, the bubbles mixed in the liquid flow path 52 float upward from below along the liquid flow, and are led out from the upper end portion 44 of the liquid flow path 52 as they are. Thereby, it is possible to prevent the bubbles from staying in the liquid flow path 52, and it is possible to prevent the heat exchange performance from being lowered and the generation of thermal stress caused by the bubbles staying in the liquid flow path 52.

  In particular, in this embodiment, since the gas flowing through the gas flow path 51 is hot and the liquid flowing through the liquid flow path 52 boils and bubbles are likely to be generated inside, the structure in which the bubbles do not stay in the liquid flow path is provided. It works more effectively.

  2ndly, according to the heat exchanger 8 of this embodiment, the flat tube 42 arrange | positioned toward an up-down direction is laminated | stacked in multiple stages at predetermined intervals, and the upper end part of the flat tube 42 adjacent to a lamination direction Since the upper tank 44 communicating with each other and the lower tank 45 communicating with the lower ends of the flat tubes 42 adjacent to each other in the stacking direction are provided, the flat tube 42, the upper tank 44, and the lower tank 45 are provided. Thus, the heat exchanger 8 can be configured simply.

  In addition, in the heat exchanger 8 of this embodiment, the flat tube 42 itself has the tank formation part 42b which communicates with the adjacent flat tube 42 and forms the tanks 44 and 45, Therefore The heat exchanger 8 is further simplified. It can be configured.

  Third, since the heat exchanger liquid inlet 47 and the heat exchanger liquid outlet 46 are provided on one outermost side (right side in FIG. 5) in the stacking direction Z of the flat tubes, one side of the heat exchanger 8 (FIG. 5). Since the pipe 55 (for example, rubber hose) on the inlet side and the pipe 54 (for example, rubber hose) on the outlet side can be attached together from the middle right side), the pipe connected to the heat exchanger liquid inlet 47 and the heat exchanger liquid outlet 46 The attachment work of 54 and 55 is simplified.

  Moreover, since it is not necessary to provide the connection space S (two-dot chain line in FIG. 5) on both sides (left and right in FIG. 5) of the heat exchanger 8, the space occupied by the heat exchanger 8 can be reduced. Therefore, it is suitable as the vehicle-mounted heat exchanger 8 in which the mounting space is limited.

  In short, the heat exchanger for a fuel cell vehicle according to the present invention includes a gas flow path through which gas flows and a liquid flow path arranged so that the flowing liquid is in thermal contact with the gas flow path. The liquid flow path is arranged in a substantially vertical direction and the liquid is led out from the upper end portion of the liquid flow path. Circulate towards. For this reason, the bubbles mixed in the liquid flow path rise upward from below along the flow of the liquid and are led out from the upper end of the liquid flow path as they are. As a result, bubbles can be prevented from staying in the liquid flow path. As a result, it is possible to prevent deterioration in heat exchange performance and generation of thermal stress caused by retention of bubbles in the liquid flow path.

FIG. 1 is a conceptual diagram of a fuel cell system. It is a top view of the vicinity of the combustor and heat exchanger of the fuel cell system. The top view of the assembly body which assembled the combustor, the heat exchanger, and the exhaust pipe. The side view of the assembly body which assembled the combustor, the heat exchanger, and the exhaust pipe. The vertical sectional view showing roughly the heat exchanger of this embodiment.

Explanation of symbols

8 ... Heat exchanger 42 ... Flat tube 42b ... Tank forming part 44 ... Upper tank 45 ... Lower tank 46 ... Pipe (heat exchanger liquid outlet)
47 ... Pipe (heat exchanger liquid inlet)
51 ... Gas channel 52 ... Liquid channel Z ... Flat tube stacking direction

Claims (3)

In a heat exchanger for a fuel cell vehicle used in a fuel cell system as a vehicle drive source,
A gas flow path through which gas flows, and a liquid flow path arranged so that the flowing liquid is in thermal contact with the gas flow path,
A heat exchanger for a fuel cell vehicle, wherein the liquid passage is arranged in a substantially vertical direction, and the liquid is led out from an upper end portion of the liquid passage. A heat exchanger for a fuel cell vehicle according to claim 1,
A plurality of flat tubes arranged in the vertical direction are stacked in multiple stages at predetermined intervals, and an upper tank is provided to connect the upper ends of the flat tubes adjacent in the stacking direction, and the lower portion of the flat tube adjacent in the stacking direction By providing a lower tank that communicates with each other,
A heat exchanger for a fuel cell vehicle, characterized in that the liquid flow path is formed in the flat tube and the gas flow path is formed between flat tubes adjacent in the stacking direction. A heat exchanger for a fuel cell vehicle according to claim 2,
A heat exchanger for a fuel cell vehicle, wherein a heat exchanger liquid inlet and a heat exchanger liquid outlet are provided on one outermost side in the stacking direction of the flat tubes.

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