Experimental Study On Influence Of Cathode Flow Field On Performance Of Proton Exchange Membrane Fuel Cell With Multiple Operating Conditions

With the depletion of fossil energy and the growing environmental problems,energy and environmental issues are becoming the main problems that constrain social development since last century.Proton Exchange Membrane Fuel Cell(PEMFC)has attracted more and more attention in terms of automotive power because of its advantages: rapid start-up,high efficiency and low pollution and it is gradually becoming a hot research topic in new energy vehicles area.Water and heat management problems of PEMFC especially cold start operating condition below 0 °C need to be solved due to the negative influence on performance and a lot of work has been done.Based on published research results,the performance of 5 cm × 5 cm PEMFC with anode serpentine flow channel under different cathode flow fields(serpentine,parallel,wavy,interdigitated)is experimentally studied in the thesis.Both normal operating condition at 70 °C and cold start operating condition below 0 °C are taken into account.In normal operating condition,the performance of PEMFC with 4 different relative humidity degree of reatant gas(80%/80%,80%/40%,40%/80%,40%/40%)is investigated,the polarization curves and power density curves are also performed and each of impedance parts is analyzed with EIS.The experiment results show that higher relative humidity reactant gas causes higher performance.The economic anlaysis including pumping loss of all flow field combinations is considered.Cold start performance of PEMFC with different flow field combinations are also researched,which includes 4 experiment modes: various start current density mode,various start voltage mode,various cathode inlet gas flux mode,various initial temeperature mode.The cold start experiment results are consisted of four parts.In various current density mode,lower current density induces lower water production speed,which leads to longer operating time.In various voltage mode,higher output voltage means lower current density and its difficulty in successful cold start becomes lower.In various cathode inlet gas flux mode,more supercooled product water can be removed from CL by larger cathode flow flux.In various initial temperature mode,higher temperature makes freezing rate become lower and the possibility of CL warming above 0 °C before it is fully filled with ice become higher,which makes operating time become longer.Also,the phenomenon that S-S has the shortest operating time and S-I has the longest operating time is explained by combining heat transfer factor(reflected by energy flow analysis)and mass transfer factor(reflect by structural analysis),which also illustrates the tight coupling relationship between heat and mass transfer phenomenon.