| Under the promotion of the policy,proton exchange membrane fuel cells with high energy density,low weight and fast charging have been comprehensively developed,especially in the field of heavy truck.However,40% ～ 60% of their energy is converted into heat during operation.If these heat cannot be effectively taken away,excessive heat will cause the fuel cell temperature to be too high and the temperature distribution is uneven.Resulting in its performance and life reduced.In view of the high heat dissipation density of proton exchange membrane fuel cells,how to effectively improve the heat dissipation efficiency,improve the internal temperature distribution uniformity,reduce the system volume and power consumption,and expand its application range is particularly important.In order to solve this problem,an experimental platform for heat dissipation performance of heavy truck fuel cells was built based on flow boiling cooling technology and separated heat pipe technology.A micro-channel parallel flow heat exchanger with compact structure and high heat exchange performance was selected and HFE-7100 was used as coolant.Compared with the traditional single-phase liquid cooling system using glycol-water solution,the temperature profiles of the heating side and the heat transfer performance of the two heat sink systems under different operating parameters were studied.The experimental results show that:(1)With the increase of ambient temperature,the heat dissipation of both cooling modes decreases,but the decrease of heat dissipation of twophase cooling mode is small.In addition,at 50℃,the heat lost by two-phase cooling was 2.45 times that by single-phase liquid cooling,and the EER increased by 132%.(2)With the increase of wind speed at the side of the heat exchanger,the heat lost by both cooling methods increased,but the system energy efficiency decreased.The change of heat lost by two-phase cooling method was smaller than that by single-phase liquid cooling method.And the experiment shows that the heat dissipation of two-phase cooling method at small wind speed is much greater than that of single-phase liquid cooling method at all wind speed.(3)When the coolant flow rate gradually increases from 3L/min to 4.5L/min,the difference between heat dissipation of two-phase cooling mode and single-phase liquid cooling mode increases from 4.8k W to 7.7k W,and the increase rate increases from 72% to 109%.At the same time,the system energy efficiency increased first and then remained unchanged or even decreased,and the optimal flow rate was 4L/min under this experimental condition,indicating that the system EER cannot be increased by blindly increasing the flow rate.(4)With the increase in the number of heat exchanger processes,the heat volume of both cooling methods showed a trend of first increasing and then decreasing,and the highest heat volume and the largest system energy efficiency ratio EER were achieved when using a 3-flow heat exchanger.(5)When two cooling methods are used to cool the heating end,the temperature distribution of the single-phase liquid-cooled cooling method increases in the flow direction linearly,with a maximum temperature difference of 30.4°C and a maximum temperature of 90°C near the outlet.The two-phase cooling method has a more uniform temperature spread and can control the temperature of the heating plate between 60 and 72°C,and can change its operating temperature by changing the pressure inside the tube.The system using two-phase cooling working medium has the advantages of high heat dissipation efficiency,good temperature distribution uniformity,wide operating temperature range,low power consumption,etc.It has good applicability in the field of vehicle fuel cells,and is worthy of promotion and application. |
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