Study On Thermal Management Approaches Of Proton Exchange Membrane Fuel Cell Via Numerical Method

Proton exchange membrane fuel cell(PEMFC)is an energy conversion device which can convert the fuel’s chemical energy into electrical energy through electrochemical reaction.Because of its advantages including zero pollution,low noise and high energy conversion efficiency,PEMFC is regarded as an ideal new energy power generation device.PEMFC has a very wide application prospect,which can be used in automotive power,mobile power and so on.In practical applications,thermal management plays a key role on its performance and stability due to the fact that if the temperature is too high,the membrane of PEMFCs will dehydrate,and if the temperature is too low,the chemical reaction rate will be reduced and the performance of PEMFC will be weakened.Besides,the non-uniformity of temperature distribution will also weaken the stability and lifetime of PEMFC.Therefore,effective thermal management is of great importance,especially for the PEMFCs with high power and PEMFC stacks.The main research objective of this paper is to study the influence of three widely commercialized flow fields on the thermal management of PEMFC stack based on numerical simulation method,and to study the potential advantages and application value of phase-change cooling as a new cooling method in PEMFC.First,the influence of flow fields on the thermal management of PEMFC stack is studied by numerical simulation in this study.Three commercially utilized flow fields including the straight flow field from Ballard,the waved flow field from Honda,and the three-dimensional mesh flow field from Toyota,are chosen and investigated.After the simulation model is built,the reliability and accuracy of the model are proved by experimental verification.At the same time,the corresponding thermal management evaluation index is defined to evaluate the influence of flow fields on thermal management of stack.The results show that the stack with3 D mesh flow field has the best performance,but the corresponding thermal management performance and the temperature uniformity are the worst,which is due to the normal phase convection brought by the repeated small cell structure of 3D mesh flow field,resulting in some local high temperature points.In contrast,the conventional two-dimensional flow fields,straight-one and waved-one,enable similar thermal management performance.Secondly,phase-change cooling strategy is proposed in this paper and its feasibility and potential advantages are demonstrated by simulation method.The results show that the phase-change cooling enables much better cooling performance and greatly improved temperature uniformity compared with conventional cooling approaches,water-cooling and air cooling,at the same coolant flow rate.For the phase-change cooling strategy,it is also found that the decrease in coolant flow rate would not worsen the cooling performance in a certain range.Moreover,a method to adapt phase-change cooling to different operating temperatures is proposed,which is to increase the boiling point of the coolant to a suitable temperature by adding pressure in the cooling channel,and the feasibility of this method is also proved by numerical simulation.