Study of thermal integration issues and heat loss pathways in a planar microscale fuel processor: Demonstration of an integrated silicon microreactor based methanol steam reformer

The onboard extraction of hydrogen by processing easily stored, high density liquid hydrocarbons seems to be the most promising method of supplying high purity hydrogen to proton exchange membrane fuel cells (PEMFCs) for portable power. Microreactor technology is a promising approach to harnessing the high energy density of hydrocarbons and is being used to produce hydrogen-rich gases by reforming of methanol and other liquid hydrocarbons. A number of crucial challenges exist for the realization of practical portable fuel processor and fuel cell systems. Based on the literature and research conducted, several of the key issues are identified. Miniaturization of system components and thermal management in miniature systems are perhaps the most crucial challenges for portable fuel processors.; Silicon microfabrication technology was explored to achieve miniaturization. In this study, a silicon microreactor-based catalytic methanol steam reforming reactor was designed, fabricated, and demonstrated in the context of complete thermal integration to understand the crucial issues and to develop a knowledge base required to rationally design and integrate the microchemical components of a fuel processor. Detailed thermal and reaction experiments were carried out to demonstrate the potential of microreactor-based on-demand H2 generation. Based on thermal characterization experiments, the heat loss mechanisms and effective convective heat coefficients from the planar microreactor structure were determined. The result provided fundamental insight of critical thermal transfer issues such as transfer of heat between reactor components, control of' temperature, insulation, and heat losses. Based on this understanding, suggestions are{09} made for scale up of reactor components and a packaging scheme for reduction of convective and radiative losses.; Keywords. portable power, microreactor, PEMFC, methanol reformer, fuel process thermal management...