BeskrivelseTo regulate the magnitude and the direction of the heat flux in an exchanger-based methanol evaporator of a fuel cell system, thermoelectric (TE) modules can be deployed as active heat pumps. The performance of the TE-integrated evaporator is strongly influenced by its heat exchange structure. The structure transfers the fuel cell exhaust heat to the evaporation chamber to gasify the methanol, where TE modules are installed in between to facilitate the heat regulation. In this work, firstly, a numerical study is conducted to determine the working currents and working modes of the TE heat regulators under the system working condition fluctuations and during the system cold start. A 3-dimensional evaporator model is generated in the computational fluid dynamics (CFD) code ANSYS FLUENT® by combining a compact TE model with a number of various heat exchange structure geometries. The compact TE model adopts order-reduction technique in both gridding and computing to improve the computation efficiency, and can extract its effective materials properties based on the parameters from module manufacturers’ datasheets. Secondly, the evaporator model is used on the active heat exchanger to minimize the thermal resistance and to assess the system pressure drop. The factors studied includes: type of the fins of the heat exchange structure, thickness of the fins, etc. Results prove that the TE-integrated evaporator can probably work more efficiently and smoothly under both fluctuation and cold start. The analysis in this paper shows that the TE-integrated methanol evaporator is of promising performance.
|Periode||10 jul. 2012|