有/无泵辅助板式蒸发器环路热管系统性能的实验研究

Experimental Study on Plate Evaporator Loop-Heat-Pipe Systems with/without Pump-Assistance

实验研究了泵辅助和无泵辅助板式蒸发器环路热管系统的启动特性、不同热流密度下系统内工质的流动传热特性和热效率,以及在一定热流密度下不同泵功率对泵辅助板式蒸发器环路热管系统的影响。结果表明:无泵辅助系统需蒸发器内产生气态工质后才开始运行并进行换热,冷凝器内的工质是相变换热,而泵辅助环路热管系统一经启动就开始运行并进行热量交换,冷凝器内的换热方式逐渐由显热换热转变到相变换热;无泵辅助系统热效率随蒸发器热流密度的升高而升高,而泵辅助系统随蒸发器热流密度的升高而降低,泵辅助系统整体热效率高于无泵系统;当热流密度为0.25 W·cm^(-2)时,泵辅助环路热管热效率较无泵辅助环路热管热效率高22.1%,而当热流密度为1.25 W·cm^(-2)时,泵辅助系统仅比无泵辅助系统高2.7%,说明当热流密度较小时,泵辅助系统更具优越性;对于泵辅助环路热管系统,系统热效率随着泵功率的增加而减小,在1.25 W·cm^(-2)热流密度下,适用的泵功率强度不应超过0.002 W·cm^(-2),表明系统热流密度与泵功率存在最优匹配。研究结果可为设计分离型平板式太阳能热水器及热沉散热器提供参考。

Starting characteristics of plate evaporator loop-heat-pipe systems with/without pump-assistance were studied,and flow heat transfer characteristics and thermal efficiency of the two systems under different heat flux were compared.Effects of different pump power on the pump-assisted system under certain heat flux were investigated.The results show that the non-pump system starts working when the evaporator generates gas working fluids,and the heat transfer in the condenser is via phase change.However,the pump-assisted system starts immediately and the heat transfer mode changes from sensible heat transfer to phase change heat transfer.Thermal efficiency of the non-pump system increases when the evaporator heat flux increases,while the pump-assisted system shows the opposite.The overall thermal efficiency of the pump-assisted system is higher.When the heat flux is0.25W·cm-2,the thermal efficiency of the pump-assisted system is22.1%higher.However,this value is2.7%when the heat flux is1.25W·cm-2.The thermal efficiency of the pump-assisted system declines with the increase of pump power intensity for static heat flux.The pump power intensity should not exceed0.002W·cm-2when the heat flux is1.25W·cm-2,and there is an optimal combination for the system heat flux and the pump power.This study provides guidelines for the design of separate flat-panel solar water heaters and heat sink radiators.