Experimental And Numerical Simulation Study On Vehicle Spray Cooling Under Vibration Environment

With the continuous development of new energy vehicles,the demand for energy density of batteries and motors is increasing,which puts higher requirements on the thermal management of on-board devices such as batteries and motors.Therefore,the development of efficient cooling systems has become an urgent problem to be addressed in the direction of automotive thermal management.Spray cooling exploits the phase transition of the cooling medium to achieve efficient heat transfer,which has the characteristics of requiring less cooling medium,good surface temperature uniformity,and high cooling efficiency.However,vibrations due to road conditions and motor operation during vehicle operation are inevitable,which leads to considerable uncertainty in the heat transfer for spray cooling.Therefore,the heat transfer performance of spray cooling under vibration has been investigated by combining experimental studies with numerical simulations by constructing a closed vibrating spray cooling testbed.First,a closed vibrating spray cooling test bench was constructed.The data acquisition and signal control monitoring interface was built using Lab VIE W software to enable real-time monitoring of test data and control signals.Uncertainty analysis of the test data was performed to verify the reliability of the testbed.Subsequently,based on the test bench,spray cooling experiments in the non-boiling region of static and vibrating surfaces were carried out.It has been found that high vibrational frequencies are beneficial for spray cooling heat transfer.As the frequency increases,the heat transfer coefficient also increases,and the heat transfer performance of spray cooling is enhanced by 9.2%.However,the heat transfer performance of spray cooling is suppressed when the resonance frequency is close to the material.Small,large amplitude and low vibration frequency conditions are not conducive to spray cooling heat transfer.As the vibration displacement increases,the heat transfer performance is suppressed by 21.9%.From the analysis of the variance,it is found that the vibrational shift has a larger effect on the spray cooling than the frequency at low heating power.At high heating power,the effect of vibration on heat transfer is reduced due to enhanced evaporation of the liquid film.To further explore the influence of vibration on the heat transfer performance of spray cooling,a numerical simulation model of spray cooling heat transfer on vibration surface was established.The influence of vibration on the heat transfer performance of spray cooling was analyzed from the perspective of temperature distribution,liquid film thickness,and liquid film velocity.The simulation results show that with the increase of heating power,the surface temperature increases,the evaporation effect is enhanced,and the thin liquid film area on the surface is larger.At high vibrational frequencies,it is found that the region of the thin liquid film on the vibrating surface is wider and the higher the frequency,the better the heat transfer effect.Under the condition of vibration displacement,the phenomenon of liquid film hysteresis occurs,and the surface instability affects the convective heat transfer process,which is not conducive to spray cooling.Finally,using the similarity principle and dimensional analysis method,based on a large number of experimental data in the paper,the dimensionless correlation of spray cooling heat transfer in non-boiling region under vibration is fitted.It is found that the Nusselt number Nu is affected by the Prandtl number Pr and Reynolds number Re.Finally,the accuracy of the correlation is improved by adding the evaporation coefficient.The maximum error accuracy of the dimensionless correlation of spray cooling heat transfer obtained by fitting is 9.7%,and the fitting result is good.