Contact heater/humidifier for fuel cell systems

#This invention relates to heat exchangers, and more particularly, to a heat exchanger that provides the additional function of heating and humidification of a gas, such as a gaseous reactant employed in a fuel cell system.

#Concerns about pollution resulting from the operation of internal combustion engines have promoted a considerable increase in interest in fuel cell systems that produce electric power for electric motors, particularly where the electric motor is employed to provide propulsion for a vehicle. Such systems are quite complex in a number of respects. For one, the multiple components of the systems are typically required to fit into a relatively small space. Further, the weight of system components when the system is used in a vehicle must be at a minimum so as to maximize fuel efficiency. Additionally, the systems must be capable of operating efficiently, with prompt response, to a variety of loading conditions corresponding to internal combustion engine operating states such as idle, on the one hand and full power on the other as well as intermediate loadings as might be utilized in a vehicle for relatively constant speed cruising.

#As is well known, the fuel cells have electrodes, one of which is subjected to gaseous fuel and another of which is subjected to a gaseous oxidant for the fuel. A typical fuel is hydrogen and a typical oxidant is the oxygen contained in air. The fuel may be molecular hydrogen provided by any of a variety of means as, for example, a source of compressed molecular hydrogen, or a hydrogen rich gas produced by catalytic processes from hydrocarbons as, for example, gasoline or diesel fuel or other organic compounds such as alcohols, most notably methanol.

#FIG. 1 is a schematic of one type of fuel cell system in which a humidifier made according to the invention may be employed;

#FIG. 2 is a partially fragmentary, perspective view of a preferred embodiment of a humidifier;

#FIG. 3 is an end elevation of the humidifier with the inlet manifold removed;

#Exemplary embodiments of the invention will be described herein in the environment of an intended use in a vehicle and one which utilizes molecular hydrogen an anode gas and an oxygen containing reactant which is employed as a cathode gas. However, it is to be understood that the invention may be employed with efficacy in nonvehicular applications, whether or not subjected to varying loads. The humidifier of the invention may also be employed with efficacy in other fuel cell systems such as reformer type fuel cell systems that employ a liquid fuel such as methanol, ethanol, gasoline, diesel fuel, etc. or gaseous fuels such as natural gas, propane or butane, etc. to generate a hydrogen rich anode gas. In a hydrogen fuel system, a humidifier such as that made according to the invention will generally be employed to humidify both the gaseous hydrogen fuel and the gaseous oxygen containing reactant, with one humidifier being disposed on the anode inlet side and another humidifier being employed on the cathode inlet side. However, it may be used in reformer type systems as mentioned above, in which case, a humidifier will typically be employed on the oxygen containing gas side, namely, the cathode side. In those instances where the reformer type system does not additionally humidify the hydrogen rich gas supplied to the anode side of the fuel cell, a humidifier may be employed in that location as well. Consequently, the invention should not be regarded as limited to vehicular systems or molecular hydrogen fuel systems except as expressly so stated in the appended claims as it is clearly applicable to nonvehicular applications as well as other fuel cell systems, including reformer type systems.

#It should also be understood that references to humidifying and increasing the dewpoint are used interchangeably and are intended to be synonymous. Further still, in many cases, but certainly not all, the humidifier will increase the temperature of the gas being humidified as it passes from the inlet to the outlet of the humidifier. But in all cases, the dewpoint of the gas is increased. Thus, references to “heating” of the gas are not intended to be limited to situations where gas exit temperature is greater than gas entry temperature. Rather, “heating” simply refers to the act of rejecting heat to the gas in the process of increasing the dewpoint of the gas as the gas travels from the inlet and the outlet.

#Turning now to FIG. 1, one type of fuel cell system with which the invention may be used is illustrated in FIG. 1. This system is specifically intended to be employed in a vehicle but may be used to advantage in other environments.