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Fuel cells are related to a number of scientific and engineering disciplines, which include electrochemistry, catalysis, membrane science and engineering, heat and mass transfer, thermodynamics and so on. Several thermophysical phenomena such as heat transfer, multicomponent transport and two phase flow play significant roles in hydrogen proton exchange membrane fuel cells and direct methanol fuel cells based on solid polymer electrolyte membrane. Some coupled thermophysical issues are bottleneck in process of scale-up of direct methanol fuel cells and hydrogen proton exchange membrane fuel cells. In present paper, experimental results of visualization of condensed water in fuel cell cathode microchannels are presented. The equivalent diameter of the rectangular channel is 0.8mm. Water droplets from the order of 0.08mm to 0.8mm were observed from several different locations in the channels. Several important problems, such as generation and change characteristics of water droplet and gas bubble, two phase flow under chemical reaction conditions, mass transfer enhancement of oxygen in the cathode porous media layer, heat transfer enhancement and high efficiency cooling system of proton exchange membrane fuel cells stack, etc., are discussed.

Fuel cells have attracted extensive attention throughout the world in recent years for their high efficiency and high environmental compatibility. Temperature plays a key role in achieving high performance of fuel cells because it deeply influences the activity of catalyst, dehydration of solid polymer membrane, mass transfer and heat management of fuel cells. The temperature distribution has close relationship with current density distribution and lifetime of fuel cells because the uniformity of temperature distribution is a quite important problem for fuel cells. In this paper, a review of temperature measurement technologies that can be used to measure temperature distribution of fuel cells was presented. The measurement of cathode exterior surface temperature fields of a hydrogen proton exchange membrane fuel cell under various operational conditions was conducted by using the technology of infrared thermal imaging. The proton exchange membrane fuel cell structure was designed for uniformity of input heat. A NEC TH5102 thermo tracer was applied to measure the cathode exterior surface temperature distributions of the cell with 5cm 2 active area. The experimental results showed that the infrared thermal imaging is an effective method to measure the exterior temperature fields of the PEMFC. The cathode temperature distributions of the cell varied with cell temperatures and flow rates.