Experimental Investigation On Heat Transfer Performance Of Pulsating Heat Pipe With Self-rewetting Nanofluids

In recent years,with the rapid development of electronic chip technology toward integration and miniaturization,the heat flux of chip increases rapidly,and the heat dissipation problem of electronic devices becomes very acute.Pulsating heat pipe is generally considered to be the most potential heat transfer element in solving the high heat flux dissipation in narrow space.Because of its advantages of simple fabrication,high heat transfer efficiency,no external power consumption,convenient carrying,strong adaptability and reliable operation.However,because its structure is simple,the method of optimizing the structure can not play the role of heat transfer enhancement.And because of the influence of thermophysical properties,pulsating heat pipes with pure working fluid can not simultaneously realize rapid start-up at low heating power and substantially heat transfer enhancement at high heating power.Based on the above considerations,the development of new working fluids is considered to be the most direct and effective way to enhance the heat transfer of pulsating heat pipes.In this paper,Al₂O₃/H₂O nanofluids and self-rewetting nanofluids prepared from n-butanol aqueous solution and graphene oxide dispersions are used as working fluids respectively.The effects of mass concentration,liquid filling ratio and vacuum degree on the heat transfer performance of pulsating heat pipe were studied experimentally.The experimental results show that,when Al₂O₃/H₂O nanofluids are used as working fluid,the optimal mass concentration and filling ratio of pulsating heat pipes are 0.3%and 50%respectively.Compared with deionized water pulsating heat pipes,it is found that the enhancement heat transfer rate of Al₂O₃/H₂O nanofluids pulsating heat pipes with mass concentration of 0.3%is as high as 10.28%when filling ratio is 50%.Different vacuum degrees of pulsating heat pipes will lead to different starting power.The higher the vacuum degree,the lower the starting power.When the heating power exceeds 90W,compared the evaporation section transient temperature of Al₂O₃/H₂O nanofluids pulsating heat pipe with that of the deionized water pulsating heat pipe,it is found that at high power,the addition of Al₂O₃/H₂O nanofluids delays the intense fluctuation of the transient temperature of the evaporation section.The heat transfer effect of self-rewetting nanofluids pulsating heat pipes with different filling ratios is different.Under the experimental conditions,when the filling ratio of self-rewetting nanofluids is 70%,the heat transfer efficiency of pulsating heat pipe is the best.Besides,the average temperature difference and average thermal resistance are the smallest.Compared with deionized water pulsating heat pipe,the enhancement rate is even as high as 29.2%.