有/无泵辅助板式蒸发器环路热管系统性能的实验研究
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摘要
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 is 0.25 W·cm~(-2), the thermal efficiency of the pump-assisted system is 22.1% higher. However, this value is 2.7% when the heat flux is 1.25 W·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 exceed 0.002 W·cm~(-2) when the heat flux is 1.25 W·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.
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 is 0.25 W·cm~(-2), the thermal efficiency of the pump-assisted system is 22.1% higher. However, this value is 2.7% when the heat flux is 1.25 W·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 exceed 0.002 W·cm~(-2) when the heat flux is 1.25 W·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.
引文
[1]QU Jian(屈健),WU Hui-ying(吴慧英).Experimental investigation on the heat transfer performance of a pulsating heat pipe charged with water/FC-72 nanoemulsion fluids(水/FC-72纳米乳液振荡热管传热特性研究)[J].Journal of Chemical Engineering of Chinese Universities(高校化学工程学报),2012,26(2):210-215.
[2]YUAN Da-zhong(袁达忠),MA Xue-hu(马学虎),FANG Zheng(房正).Fluid flow and heat transfer characteristics of a two-phase closed thermosyphon(两相闭式热虹吸管的流动与传热特性)[J].Journal of Chemical Engineering of Chinese Universities(高校化学工程学报),2008,22(4):557-562.
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[4]Singh R,Nguyen T,Mochizuki M.Capillary evaporator development and qualification for loop heat pipes[J].Applied Thermal Engineering,2014,63(1):406-418.
[5]WANG Ye(王野),JI Xian-bing(纪献兵),ZHENG Xiao-huan(郑晓欢),et al.Capillary pumping characteristics of sintered porous wicks for loop heat pipes(环路热管烧结毛细芯的抽吸特性)[J].Journal of Chemical Engineering of Chinese Universities(高校化学工程学报),2016,30(3):560-565.
[6]Schweizer N,Stephan P,Schlitt R.A concept for a miniature mechanically pumped two-phase cooling loop[J].[2018-06-29].https://doi.org/10.4271/2008-01-1953.
[7]Zhang S,Ma G,Zhou F.Experimental study on a pump driven loop-heat pipe for data center cooling[J].Journal of Energy Engineering,2014,1(14):04014054.
[8]He W,Hong X Q.Operational performance of a novel heat pump assisted solar facade loop-heat-pipe water heating system[J].Applied Energy,2015,146(371):371-382.
[9]Park C,Vallury A,Zuo J.Performance evaluation of a pump-assisted,capillary two-phase cooling loop[J].Journal of Thermal Science and Engineering Applications,2009,1(12):022004.
[10]LI Qiang(李强),ZHOU Hai-ying(周海迎),XUAN Yi-min(宣益民).Investigation on heat transfer characteristics of composite capillary evaporator(复合结构毛细蒸发器传热特性研究)[J].Journal of Engineering Thermophysics(工程热物理学报),2008,29(1):148-150.
[11]WEI Xin-li(魏新利),GUAN Zhong-jie(关中杰),ZHANG Wei-long(张伟龙).Investigation of starting and filling ratio characteristics of loop heat pipes with plate-type evaporator(平板蒸发器环路热管启动及充灌率特性研究)[J].Journal of Thermal Science and Technology(热科学与技术),2018,17(3):191-197.
[12]HE Jiang(何江),LIN Gui-ping(林贵平),BO Li-zhan(柏立战).Adverse effect of non-condensable gas on the operating performance of loop heat pipe(不凝气体对环路热管工作性能的不利影响)[J].Journal of Aerospace Power(宇航动力学报),2014,29(10):2377-2384.
[2]YUAN Da-zhong(袁达忠),MA Xue-hu(马学虎),FANG Zheng(房正).Fluid flow and heat transfer characteristics of a two-phase closed thermosyphon(两相闭式热虹吸管的流动与传热特性)[J].Journal of Chemical Engineering of Chinese Universities(高校化学工程学报),2008,22(4):557-562.
[3]Maydanik Y F,Vershinin S V,Pastukhov V G,et al.Loop heat pipes for cooling systems of servers[J].IEEE Transactions on Components and Packaging Technologies,2010,33(2):416-423.
[4]Singh R,Nguyen T,Mochizuki M.Capillary evaporator development and qualification for loop heat pipes[J].Applied Thermal Engineering,2014,63(1):406-418.
[5]WANG Ye(王野),JI Xian-bing(纪献兵),ZHENG Xiao-huan(郑晓欢),et al.Capillary pumping characteristics of sintered porous wicks for loop heat pipes(环路热管烧结毛细芯的抽吸特性)[J].Journal of Chemical Engineering of Chinese Universities(高校化学工程学报),2016,30(3):560-565.
[6]Schweizer N,Stephan P,Schlitt R.A concept for a miniature mechanically pumped two-phase cooling loop[J].[2018-06-29].https://doi.org/10.4271/2008-01-1953.
[7]Zhang S,Ma G,Zhou F.Experimental study on a pump driven loop-heat pipe for data center cooling[J].Journal of Energy Engineering,2014,1(14):04014054.
[8]He W,Hong X Q.Operational performance of a novel heat pump assisted solar facade loop-heat-pipe water heating system[J].Applied Energy,2015,146(371):371-382.
[9]Park C,Vallury A,Zuo J.Performance evaluation of a pump-assisted,capillary two-phase cooling loop[J].Journal of Thermal Science and Engineering Applications,2009,1(12):022004.
[10]LI Qiang(李强),ZHOU Hai-ying(周海迎),XUAN Yi-min(宣益民).Investigation on heat transfer characteristics of composite capillary evaporator(复合结构毛细蒸发器传热特性研究)[J].Journal of Engineering Thermophysics(工程热物理学报),2008,29(1):148-150.
[11]WEI Xin-li(魏新利),GUAN Zhong-jie(关中杰),ZHANG Wei-long(张伟龙).Investigation of starting and filling ratio characteristics of loop heat pipes with plate-type evaporator(平板蒸发器环路热管启动及充灌率特性研究)[J].Journal of Thermal Science and Technology(热科学与技术),2018,17(3):191-197.
[12]HE Jiang(何江),LIN Gui-ping(林贵平),BO Li-zhan(柏立战).Adverse effect of non-condensable gas on the operating performance of loop heat pipe(不凝气体对环路热管工作性能的不利影响)[J].Journal of Aerospace Power(宇航动力学报),2014,29(10):2377-2384.