Research On Vibration Enhanced Heat Transfer And Flow Characteristics Of Automotive Radiator

Radiator as one of the key components in the automotive cooling system,its structure and performance directly affects the compactness and heat dissipation effect of the whole cooling system,and plays an important role in the power of the vehicle.The heavy load,high heat production and low driving speed of engineering vehicles make their requirements for radiators to be able to dissipate heat efficiently more prominent,and at the same time,the vehicle itself will inevitably be accompanied by vibration when working,and the existence of vibration conditions provides a new direction for improving the performance of automotive radiators.Therefore,this paper investigates the performance of an automotive serrated fin radiator based on the vibration-enhanced heat transfer theory and using computational fluid dynamics.Through the comparative analysis at two different states,static and vibrating,a better understanding of the mechanism of the effect of vibration on the performance of automotive radiators is provided to improve the heat dissipation efficiency from both the perspective of its own structure and vibration conditions.The main contents are as follows:(1)The existing serrated fin radiator structure has been improved to obtain a new serrated fin structure with better performance.By providing different shapes of grooves and bumps on the surface of the conventional serrated fin radiator and changing the structure of the windward side of the fins to round,both heat dissipation and pressure drop loss are improved simultaneously.The shape of the grooves and projections on the surface of the new serrated fin radiator was determined to be circular,with a radius of0.15 mm,where the balance of heat transfer and pressure drop loss is optimal.Compared with the conventional serrated fins,the average pressure drop loss is basically unchanged,and the average improvement in heat transfer and overall performance is 8.7%.(2)The heat dissipation performance of the new serrated fin heat sink is studied in the vibration state,and the vibration can indeed enhance the heat transfer compared with the static state.Numerical simulations were performed to obtain the distribution of temperature,velocity and flow fields of the heat sink unit in both stationary and vibrating states.The changes of temperature,velocity and flow fields in one simple harmonic vibration cycle are analyzed in detail,and the differences of temperature,velocity and flow fields between stationary and vibration are compared and analyzed.The results show that the vibration will increase the temperature difference between the cold air and the hot fins and improve the heat transfer environment.At the same time,the vibration will disturb the air flow and change the air flow direction,so that the air flows more towards the fin wall and forms a certain angle with the wall,which hinders the development of the boundary layer.When the fin wall vibrates at f = 15 Hz and A =4 mm,the pressure drop loss increases by only 1.7% and the heat transfer efficiency increases by 22.6% compared to the stationary condition.(3)The effect of different parameters on the vibration-enhanced heat transfer was studied,and the mechanism of vibration-enhanced heat transfer was analyzed based on the field synergy principle.The effects of different vibration parameters such as frequency and amplitude and external parameters such as wind speed and ambient temperature on the heat transfer performance of vibration strengthening were studied.The results show that when the amplitude is increased when the amplitude is small or the frequency is increased when the amplitude is small,the effect on the vibration-enhanced heat transfer is less efficient at this time.Therefore,when using vibration for enhanced heat transfer,a suitable combination of frequency and amplitude needs to be selected within the appropriate frequency and amplitude range.There is a critical wind speed,and the low wind speed is more conducive to the performance of vibration-enhanced heat transfer.The influence of ambient temperature on vibration-enhanced heat transfer is small.Vibration is used to achieve enhanced heat transfer by changing the angle between the temperature and velocity fields,and a small field synergy angle is more conducive to convective heat transfer.