复合吸液芯微细直径热管的传热性能分析
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摘要
对3种复合吸液芯微细直径热管(外径2 mm)进行了理论分析和实验研究,3种吸液芯分别为铜粉丝网复合吸液芯(SMCP)、泡沫铜丝网复合吸液芯(SMCF)和复合丝网吸液芯(MSM);结合毛细极限理论分析了这3种热管的极限传热功率,并分析其在不同充液率下的极限传热功率、轴向温度分布和蒸发冷凝热阻特性.结果表明:SMCP、SMCF和MSM热管的最佳充液率分别为110%、95%和90%,此时其极限传热功率均为7 W,与理论计算值接近;3种热管的轴向温差随着加热功率的增大而增大,其轴向温差最大值分别为4.22、4.20和4.90℃;随着加热功率的增大,蒸发热阻逐渐增大;充液率较低时,冷凝热阻变化幅度不大,充液率较高时,SMCP热管的冷凝热阻出现较大幅度波动,而SMCF和MSM热管的冷凝热阻相对稳定;当3种热管的充液率为各自最佳充液率且加热功率为7 W时,其蒸发热阻分别为0.437、0.493和0.591℃/W,冷凝热阻分别为0.167、0.106和0.110℃/W.
In this paper theoretical and experimental studies are conducted on three kinds of micro-diameter heat pipes( MDHPs,their outer diameter is 2 mm) with composite wick. The composite wicks consist of copper powdermesh( SMCP),copper foam-mesh( SMCF) and mesh-mesh( MSM). By referring to the capillary limit theory,the heat transfer power of the three kinds of MDHPs is analyzed and at the same time,maximum heat transfer capability under different filling ratios,the axial temperature distribution and the evaporation and condensation thermal resistances are analyzed. The results indicate that the maximum heat transfer capabilities of the three are 7 W,with the corresponding optimum filling ratios of SMCP,SMCF and MSM being 110%,95% and 90% respectively,which are close to the theoretical values of capillary limit. The axial temperature differences of MDHPs increase with the heating power,and the maximum values are 4. 22,4. 20 and 4. 90 ℃ respectively. With the increase of heating power,the evaporation thermal resistance increases gradually. The change of condensation thermal resistance is small under low filling ratio. With high filling ratio,condensation thermal resistance of SMCP heat pipe fluctuates greatly,while condensation thermal resistances of SMCF and MSM heat pipes are relatively stable. When the filling ratios of the three kinds of MDHPs and their respective optimum filling ratios and heat transfer performance reach 7 W,their evaporation resistances of MDHPs are 0. 437,0. 493 and 0. 591 ℃/W,and their condensing heat resistances are 0. 167,0. 106 and 0. 110 ℃/W,respectively.
In this paper theoretical and experimental studies are conducted on three kinds of micro-diameter heat pipes( MDHPs,their outer diameter is 2 mm) with composite wick. The composite wicks consist of copper powdermesh( SMCP),copper foam-mesh( SMCF) and mesh-mesh( MSM). By referring to the capillary limit theory,the heat transfer power of the three kinds of MDHPs is analyzed and at the same time,maximum heat transfer capability under different filling ratios,the axial temperature distribution and the evaporation and condensation thermal resistances are analyzed. The results indicate that the maximum heat transfer capabilities of the three are 7 W,with the corresponding optimum filling ratios of SMCP,SMCF and MSM being 110%,95% and 90% respectively,which are close to the theoretical values of capillary limit. The axial temperature differences of MDHPs increase with the heating power,and the maximum values are 4. 22,4. 20 and 4. 90 ℃ respectively. With the increase of heating power,the evaporation thermal resistance increases gradually. The change of condensation thermal resistance is small under low filling ratio. With high filling ratio,condensation thermal resistance of SMCP heat pipe fluctuates greatly,while condensation thermal resistances of SMCF and MSM heat pipes are relatively stable. When the filling ratios of the three kinds of MDHPs and their respective optimum filling ratios and heat transfer performance reach 7 W,their evaporation resistances of MDHPs are 0. 437,0. 493 and 0. 591 ℃/W,and their condensing heat resistances are 0. 167,0. 106 and 0. 110 ℃/W,respectively.
引文
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[18]李勇,陈春燕,曾志新.纤维复合沟槽吸液芯微热管的传热性能实验[J].华南理工大学学报(自然科学版),2013,41(7):45-49,55.LI Youg,CHEN Chun-yan,ZENG Zhi-xin.Experimental investigation into heat transfer performance of micro heat pipe with fiber-combined grooved wick[J].Journal of South China University of Technology(Natural Science Edition),2013,41(7):45-49,55.
[2]HOSSAIN R A,CHOWDHURI M A K,FEROZ C M.Design fabrication and experimental study of heat transfer characteristics of a micro heat pipe[J].Jordan Journal of Mechanical and Industrial Engineering,2010,4(5):531-542.
[3]GRIMES R,WALSH E,WALSH P.Active cooling of a mobile phone handset[J].Applied Thermal Engineering,2010,30:2363-2369.
[4]SETOH G,TAN F L,FOK S C.Experimental studies on the use of a phase change material for cooling mobile phones[J].International Communications in Heat and Mass Transfer,2010,37:1403-1410.
[5]YANG X,YAN Y Y,MULLEN D.Recent developments of lightweight,high performance heat pipes[J].Applied Thermal Engineering,2012,33/34:1-14.
[6]WONG S C,LIOU J H,CHANG C W.Evaporation resistance measurement with visualization for sintered copperpowder evaporator in operating flat-plate heat pipes[J].International Journal of Heat and Mass Transfer,2010,53:3792-3798.
[7]WONG S C,TSENG H H,CHEN S H.Visualization experiments on the condensation process in heat pipe wicks[J].International Journal of Heat and Mass Transfer,2014,68:625-632.
[8]LIN K T,WONG S C.Performance degradation of flattened heat pipes[J].Applied Thermal Engineering,2013,50:46-54.
[9]LI Y,HE H F,ZENG Z X.Evaporation and condensation heat transfer in a heat pipe with a sintered-grooved composite wick[J].Applied Thermal Engineering,2013,50:342-351.
[10]CHEN J S,CHOU J H.Cooling performance of flat plate heat pipes with different liquid filling ratios[J].International Journal of Heat and Mass Transfer,2014,77:874-882.
[11]LIPS S,LEFVRE F,BONJOUR J.Combined effects of the filling ratio and the vapour space thickness on the performance of a flat plate heat pipe[J].International Journal of Heat and Mass Transfer,2010,53:694-702.
[12]LI Y,CHEN S L,HE B L,et al.Effects of vacuuming process parameters on the thermal performance of composite heat pipes[J].Applied Thermal Engineering,2016,99:32-41.
[13]LI Y,ZHOU W J,HE J B,et al.Thermal performance of ultra-thin flattened heat pipes with composite wick structure[J].Applied Thermal Engineering,2016,102:487-499.
[14]CHI S W.Heat pipe theory and practice[M].Washington D C:Hemisphere Publishing Corporation,1976.
[15]CHI J S W.Mathematical modeling of high and low temperature heat pipes[R].Washington:George Washington University,1971.
[16]KLINE S J,MCCLINTOCK F A.Describing uncertainties in single-sample experiments[J].Mechanical Engineering,1953,75(1):3-8.
[17]费业泰,陈晓怀,秦岗,等.误差理论与数据处理[M].7版.北京:机械工业出版社,2017.
[18]李勇,陈春燕,曾志新.纤维复合沟槽吸液芯微热管的传热性能实验[J].华南理工大学学报(自然科学版),2013,41(7):45-49,55.LI Youg,CHEN Chun-yan,ZENG Zhi-xin.Experimental investigation into heat transfer performance of micro heat pipe with fiber-combined grooved wick[J].Journal of South China University of Technology(Natural Science Edition),2013,41(7):45-49,55.