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分别以蒸馏水和无水乙醇为工质在闭式循环喷雾冷却系统上研究了喷雾流量、表面结构、喷雾工质对传热性能的影响。从对流换热和相变换热比例关系的角度对实验数据进行了整理。结果表明:随喷雾流量的增加,热流密度增加、相变换热份额降低。当水喷雾流量为227.1 g/min、表面温度为74.32℃时,热流密度达到6.8×105W/m2;表面温度对换热有较大影响,温度越高换热性能愈强,无水乙醇的换热始终强于蒸馏水,特别是表面温度较高时,强化换热效果更为明显;其相变份额同样始终大于蒸馏水,表面温度为50℃、流量同为27.52 g/min时,蒸馏水的相变换热份额仅为20.4%,而无水乙醇的达到55.5%。微结构表面虽然减弱了对流换热能力,但减薄了液膜厚度,增强相变换热能力,使换热效果大幅提升。给出了反映表面温度影响的无量纲准则方程。
The effects of spray flow, surface structure and spray working medium on the heat transfer performance were studied on a closed-cycle spray cooling system using distilled water and anhydrous ethanol as the working fluid respectively. The experimental data are sorted from the perspective of the proportional relationship between convective heat transfer and phase change heat transfer. The results show that as the spray flow rate increases, the heat flux density increases and the phase transformation heat transfer fraction decreases. When the water spray flux is 227.1 g / min and the surface temperature is 74.32 ℃, the heat flux density reaches 6.8 × 105W / m2. The surface temperature has a great influence on the heat transfer. The higher the temperature is, the stronger the heat transfer is. Heat is always stronger than distilled water, especially when the surface temperature is higher, the effect of heat transfer enhancement is more obvious. The phase transition share is always higher than that of distilled water. When the surface temperature is 50 ℃ and the flow rate is 27.52 g / min, The share of heat transfer is only 20.4%, while the absolute ethanol reached 55.5%. Though the microstructure surface weakened the convective heat transfer capability, the thickness of the liquid film is thinned and the phase transformation heat capacity is enhanced, so that the heat exchange effect is greatly enhanced. The dimensionless criterion equation that reflects the influence of surface temperature is given.