| Aiming at the problem that the thermal management system of the full-power fuel cell passenger vehicle is difficult to dissipate heat under high temperature climbing conditions,this paper develops a scheme of spray cooling the radiator in the engine compartment by using the fuel cell reaction product water.The effectiveness of spray cooling and the effect of spray cooling on the heat dissipation performance of the radiator and the thermal management system of the vehicle are studied by numerical simulation and experimental verification methods,mainly including the following research contents:(1)The topology diagram of the radiator spray cooling system based on the recovery of the water produced by the fuel cell is constructed.According to the size of the radiator of the real vehicle,the cooling scheme of the eight nozzles up and down double row inclined arrangement and intermittent spraying is determined;the cooling mechanism of the evaporative condenser is used to analyze the radiator Spray cooling process;According to the water production mechanism of the fuel cell,a rapid calculation model of the water recovery amount of the spray system is established.(2)The numerical simulation of radiator spray cooling is realized by STAR-CCM+,and the high temperature climbing condition of the vehicle is selected as the simulation input condition,and the influence law of the spray angle and spray flow on the heat dissipation performance of the radiator under the influence of the external wind speed is analyzed,and the results under this working condition are obtained.The best spray angle and spray flow rate for single-nozzle spray cooling of radiator.(3)The radiator spray cooling experimental bench was built,and the accuracy of the numerical simulation of the radiator spray cooling was verified through experiments;the experiment obtained the curve of the temperature difference between the inlet and outlet of the radiator coolant with time,which was divided into 5 main parts according to the shape of the curve.According to the analysis of the heat transfer mode of the radiator spray cooling,the stage Ⅰ is mainly the droplet impingement heat transfer process,the stage Ⅱ is mainly the liquid film convection heat transfer process,and the stages Ⅲ～Ⅴ are mainly the liquid film evaporation heat transfer process.It can be seen from the actual observation that the humidity around the radiator in stage Ⅲ is high,the evaporation rate of the liquid film is slow,the convective heat transfer of the liquid film is weakened,and the fins of the radiator are covered with a liquid film,the air convection heat transfer of the radiator is blocked,and the heat dissipation effect is the worst.In the selection of actual spray parameters,it should be avoided that the temperature difference between the inlet and outlet of the coolant at this stage is lower than the temperature difference of the original vehicle-mounted radiator during operation;after that,the spray cooling effect of the radiator under different spray durations was studied,and the spray economy index was introduced.In the intermittent spray strategy,the optimal spray time in a single spray cycle is 20 s.Finally,the empirical formula of the evaporation rate of the water surface is modified by combining the radiator liquid film coverage and the effective spray coefficient,and a new method for radiator spray cooling is proposed.The calculation method of the heat dissipation power and the evaporation rate of the liquid film is carried out,and the reliability of the method is verified by experiments.(4)Through the calculation method of spray cooling heat dissipation power and liquid film evaporation rate,it is concluded that the balance water required by the spray cooling system is 2336.81 g and the increased heat dissipation power is11.35 k W under the high temperature climbing condition of the full-power fuel cell passenger vehicle..GT-COOL software is used to build a fuel cell cooling circuit model considering spray cooling.The simulation results show that the application of spray cooling under high temperature climbing conditions can reduce the total power consumption of the fuel cell cooling circuit system by 47.7%;if the cooling is not changed Fan and water pump speed,this solution can reduce the volume of the radiator by 15.9%.In this thesis,the research on the heat dissipation performance of fuel cell vehicle radiator based on spray cooling is carried out,and the radiator spray cooling scheme is proposed.The influence of spray flow and spray inclination on the heat dissipation performance of the radiator is revealed through numerical simulation,and the radiator spray is analyzed by using the experimental bench.The cooling heat transfer process verifies the calculation method of the spray cooling power,and proves the effectiveness of the spray cooling scheme in the thermal management of full-power fuel cell passenger vehicles,which can provide a reference for the design of the simulation and experimental platform of the spray cooling system.It provides a new idea for the design of thermal management system for high-power fuel cell vehicles. |
