Numerical and Experimental study on theThermal Characteristics of Steam Reformer for 5kW PEMFC

Abstract

The analysis of 5kW Cylindrical natural gas steam reformer is carried out experimentally and numerically with special attention on thermal characteristics. The evaluation system is configured to probe the thermal and chemical characteristics of the steam reformer. A reactor unit equipped with nickel based catalysts was designed to actived the steam reforming reaction without the inclusion of high temperature shift and low temperature shift processes. Reactor temperature distribution and its overall thermal efficiency depend on various inlet conditions such as the equivalence ratio, the steam to carbon ratio, and the fuel distribution ratio into the reactor and the combustor components. These experiments attempted to analyze the reformer's thermal and chemical properties through quantitative evaluation of product composition and heat exchange between the combustor and the reactor. FDR is critical factor in determining the overall performance as unbalanced fuel injection into the reactor and the combustor deteriorates overall thermal efficiency. Local temperature distribution als influences greatly on the fuel conversion rate and thermal efficiency. for the experiments, the operation conditions were set as SCR was in range of 2.5 to 4.0 and FDR was in 0.4 to 0.7 alonf with equivalence ratio of 0.9 to 1.1; optimum results were observed for FDR of 0.63 and SCR of 0.3 in the cylindrical steam reformer. The acquired experimentsl data is used for the validation of our proposed numerical model. The combination of experimetal and numerical data provides detailed information leading to better understanding the internal reaction mechanism. The results indicate that the thermal efficiency can be enhanced through appropriate managements of combustor heat, reactant concentration, and inflowing rates taht can be implemented by inlet gas control into both main reactor and combustor. parametirc study of the operation control variables such as steam to carbon ratio and combustible reactant ration could determine the optiomal values for the highes thermal performance.