| A proton exchange membrane fuel cell(PEMFC)is a power generation device that converts chemical energy stored in hydrogen energy into electrical energy.PEMFCs have attracted widespread attention due to their high energy conversion efficiency,fast start-up,and low emissions.A large amount of heat is generated during the actual operation of the fuel cell stack.In this thesis,from the perspective of thermal management of fuel cells,aiming at improving the uniformity of PEMFC temperature distribution and reducing pressure loss,a multiple-input multiple-output(MIMO)cooling plate flow field is proposed,and a numerical calculation model of the cooling flow field is established.The heat dissipation performance of the PEMFC cooling plate under the action of the cooling water flow direction was analyzed,and the flow field structure of the parallel cooling plate was analyzed by characteristics,and the effect of the geometrical characteristics of the flow channel on the heat dissipation performance of the flow field was obtained.First,a multi-input multi-output cooling plate flow field is proposed.The mathematical model was established by CFD method,and the effect of the MIMO cooling plate flow field in different inlet and outlet directions on the cooling performance of the fuel cell stack was studied.The effects of different inlet flow rates and inlet and outlet types on the fuel cell flow distribution,temperature distribution and pressure drop in the flow field were analyzed.The results show that the thermal properties of the serpentine flow field with parallel inlets is the best.The serpentine flow field improves the uniformity of flow distribution and avoids the generation of local hot spots.Compared with the parallel flow field,the maximum temperature value is reduced to322.7K.Secondly,a MIMO serpentine cooling plate flow field is designed to improve the heat spreading ability of the PEMFC.The effects of the number of cooling channels,cooling water flow direction,flow rate and temperature on the temperature,pressure and liquid water distribution of the fuel cell were studied.The results show that,compared with the single-channel flow field,the MIMO flow field has a smaller pressure drop and better heat dissipation,which alleviates the flooding problem of the PEMFC.When the cooling water flows downstream,the temperature difference on the membrane is the smallest,and the cooling effect is the best.The temperature on the fuel cell membrane decreases gradually with the increase of the cooling water flow rate.The smaller the temperature difference between the cooling water and the gas in the flow channel,the better the temperature uniformity of the cell.Finally,based on the single-variable analysis principle,the parametric analysis of the Z-type MIMO parallel cooling plate flow field structure is carried out.The effects of the parallel flow channel width,flow channel spacing and flow channel depth of the fuel cell cooling plate on the flow distribution uniformity and heat dissipation characteristics of the cooling plate were studied.The results show that keeping the other geometric dimensions constant,increasing the width of the flow channel can significantly improve the uniformity of flow distribution and the thermal properties of the cooling plate.When the runner spacing is reduced,the number of runners increases,and the flow difference between runners decreases,which effectively improves the uniformity of flow distribution and improves the heat dissipation capability of the PEMFC cooling plate. |
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