Design And Analysis Of Proton Exchange Membrane Fuel Cells Thermal Management System For Road Vehicles

The development of hydrogen energy and fuel cell vehicle(FCV)industry in the background of carbon peak and carbon neutrality welcomes unprecedented opportunities.Proton Exchange Membrane Fuel Cell(PEMFC)has the advantages of fast start-up,high reliability,low operating temperature(333.15 K～363.15 K)and high energy density,which is one of the important applications to promote energy innovation and achieve the dual carbon goal in traffic field.During the working process,about 50% of the chemical energy of the PEMFC stack is converted into electrical energy to drive the FCV,and the rest is dissipated in the form of heat energy.Designing an effective thermal management system to ensure that the stack is within the proper operating temperature range is critical to the output performance,safety and reliability,and service life of vehicle PEMFC stacks.The main target of this research paper is to explore the possibility and feasibility of heat pipe technology for the thermal management of vehicle PEMFC stacks.Therefore,in order to meet the thermal management requirements of an FCV currently using a liquid-cooled thermal management scheme,design work and numerical simulation of the performance of the thermal management system based on the Pulsating Heat Pipe(PHP)technology is carried out.The main work and conclusions are as follows:(1)Combining the basic parameters and thermal management requirements of the current liquid cooling system of an FCV stack,the liquid cooling system is checked and designed.Based on the estimated total coolant flow rate into the stack,the cooling channels are designed,the cooling channel dimensions are determined,and the overall structural parameters of the stack including the liquid cooling system are obtained.(2)By establishing the multi-field coupled model of the liquid cooling system,the temperature distribution of PEMFC with different coolant inlet flow rates and temperatures and the surface uniform temperature characteristics of the bipolar plate are obtained.A threedimensional single-channel non-isothermal model of the vehicle PEMFC is established,and the Bruggeman equation used for oxygen diffusion in the model is modified,and the temperature distribution of the PEMFC under three different cooling schemes are studied and comparatively analyzed.The scheme in which the coolant on the anode and cathode plates enters from different sides is obtained as the better cooling scheme.(3)A new PHP-based thermal management scheme for vehicle PEMFC is proposed.The design of the PHP is carried out,including the structural design,the selection of working fluid and filling rate,the determination of the number of bends and the angle of inclination,and the design work of the cooling plate and the secondary cooling section.In which the Water Jacket,PHP,and Cooling Plate are made into a single unit,and a cooling plate is used to take away the heat dissipated by multiple single cells.Finally,the design work of the PHP-based vehicle PEMFC stack cooling system is completed.(4)The PHP internal liquid and vapor plugs are modeled to analyze the PHP oscillation characteristics.The results show that during the working of PHP,the internal liquid plug movement is mainly influenced by the driving force the most;the liquid plug is doing back-andforth oscillation movement,and the trend is unidirectional;the larger the internal diameter of PHP is,the more violent the oscillation of the liquid plug becomes.For the designed PHP,the thermal resistance model is established and the total thermal resistance of the PHP is obtained as0.0521 K/W and the equivalent thermal conductivity is 130,000 W/(m·K).(5)A PHP-based multi-physical field coupling model of the vehicle PEMFC cooling system is established,and multi-field coupling simulations are carried out.where the space occupied by the PHP is considered as an isotropic solid with an equivalent thermal conductivity of 130,000W/(m·K).The results show that the better flow velocity of the water jacket inlet coolant is 0.05m/s and the better inlet temperature is 333.15 K.Comparing the two thermal management schemes,the results show that the temperature fluctuation of the PEMFC under the liquid-cooled scheme is larger than that under the PHP scheme;although the temperature rise of the stack under the liquid-cooled scheme is smaller,the temperature difference of the stack under the PHP scheme is smaller,with better temperature uniformity and more reasonable temperature distribution;the value on the large surface provided by the liquid-cooled scheme is 1.63 K,while the value under the PHP scheme is only 0.43 K.The PHP solution provides a cooled large surface with a better temperature uniformity.In summary,this paper provides a new thermal management scheme for FCV based on PHP technology,and evaluates the performance of the PHP thermal management system through a detailed multi-field coupled numerical simulation study.The new thermal management scheme and model evaluation method proposed in this paper can provide a reference for future thermal management research of vehicle PEMFC stacks.