Research On Spray Cooling Of Avionic Devices

With the rapid development of semiconductor technology,the problem of heat dissipation in avionics devices has become increasingly prominent.How to efficiently cool avionics devices and control their temperature within a safe range has become an important issue in securing aviation safety.The spray cooling technology has become one of the important means to solve the problem of heat dissipation of avionics devices due to its high heat transfer efficiency,low use of working medium,and uniform temperature at the heat exchange surface.In this paper,the effects of spray height,spray angle,spray pressure,and heating power on the spray cooling performance were studied by establishing an experimental platform.The working conditions were analyzed and experimental support was provided for the application of avionics spray cooling system.Firstly,the experimental study of smooth heat transfer surface under normal temperature and atmospheric pressure is carried out.The main work is as follows: 1.Experiments are carried out around the critical height,and the spray pressure,the injection angle when the heating power are kept constant.It is pointed out that there is a spray height that optimizes the spray cooling,but the according spray height is less than the critical height.2.Through theoretical calculation,the effect of spray pressure on the spray particle size and droplet rate is explored.Based on the above results,the influence curve of the spray pressure on the heat exchange effect is analyzed.The experiment proves that the spray pressure is 0.6MPa where the spray cooling effect is the best and the increase of spray pressure increases firstly yet leads to decrease of heat flux afterwards.3.For inclined spray,the influence of two kinds of inclined ways with fixed height change angle,spray bottom circle and inner inscribed with heat exchange surface on heat exchange effect are analyzed.It is pointed out that the second kind of inclined ways can promote heat exchange and get the best heat transfer effect at 30 degrees.With the increase of heating power,the heat transfer coefficient of spray cooling decreases,and when the spray pressure is low,this trend is more obvious.Furthermore,the effect of spray height,spray pressure,heating power and pressure on the spray chamber pressure on the heat exchange was studied under low pressure.The results show that the pressure of the spray chamber has an obvious lifting effect on the heat exchange capacity,and the heat flux density increases exponentially when the pressure of the spray chamber is lowered gradually.The low chamber pressure condition promotes nucleate boiling of the heat exchanger surface,and the maximum heat flux is increased by nearly 100% compared with the normal pressure condition.At the same time,the temperature of the heat exchange surface is also higher than that under normal pressure,but the temperature is generally within the safe working range.