不凝气体对竖管太阳能海水淡化装置性能的影响

EFFECTS OF NON-CONDENSABLE GASES ON PERFORMANCE OF VERTICAL TUBULAR SOLAR SEAWATR DESALINATION DEVICE

针对太阳能海水淡化装置内不凝气体抑制气水混合物冷凝换热的问题,设计一种竖管太阳能海水淡化装置,通过分别填充氦气和空气作为蒸发冷凝腔工作介质,研究2种不凝气体对装置产水速率、蒸发冷凝温差、热扩散系数以及竖直温度梯度分布等性能的影响机理。结果表明,该淡化装置加热温度为80℃时,填充氦气的装置产水速率为245 g/h,比填充空气的装置产水速率增加15%,填充氦气的装置上测点温度与下测点温度相差约0.1℃,基于试验数据给出不凝气体为氦气运行条件下装置内Nu与Ra的经验关联式,二者呈指数函数关系,决定系数为0.9926。

A novel vertical tubular seawater desalination unit which can be driven by solar energy had been designed and constructed,with an aim to investigate the effects of non-condensable gases on restraining the condensation heat transfer process. An experimental and theoretical analysis are carried out to investigate how the water yield,evaporation and condensation temperature difference,temperature gradient along vertical surface,and thermal diffusivity coefficient are affected by non-condensable gases,which are selectedas air and helium. The research results indicate that,when the heating temperature is 80 ℃ and the carrier gas is helium gas medium,the water yield can reach to 245 g/h. It is increased by 15.0% than the carrier gas of air. The temperature difference between the top shell and bottom shell is about 0.1 ℃. A new empirical correlation for the Nusselt number and Rayleigh number was fitted by using a consolidated data as the carrier gas is helium gas medium. The Nusselt number attenuated exponentially with the Rayleigh number,the adjusted R^2 value for the data fit was 0.9926.