Study On Heat Transfer Characteristics Of Micro Size Heat Pipe For Novel Passive 3D Chip Cooling

In this paper,a micro size heat pipe structure for the passive 3D chip cooling is proposed,and the natural convective boiling heat transfer characteristics of the micro channel are studied.With Ni-Cr alloy surface as heat transfer surface,deionized water and R113 as the heat transfer fluids,the influences of inclination,length and width on CHF are studied.Based on the previous research and the experimental results,a new formula for CHF is put forward.The error between the experimental results and the new formula is within 30%.For the same micro channel,with deionized water as the heat transfer fluid,SiO₂ nano fluid modifying surface has little effect on the CHF of vertical micro channel,Cu,CuO and Al₂O₃ nano fluids modifying surfaces can all improve the CHF of vertical micro channel.The optimal mass fractions of those nano particles are 0.75%,1%,1%respectively.With Ni-Cr alloy surface as heat transfer surface,adding SDS into deionized water can improve the CHF of the vertical and horizontal micro channels about 38%-72%and 31%-65%respectively,the optimal SDS concentration is 2000ppm.With optimal nano fluids modifying surfaces as heat transfer surfaces,adding SDS into deionized water can still improve the CHF of vertical micro channel,the optimal SDS concentrations for Cu,CuO and Al₂O₃ nano fluid modified surfaces are 2500ppm,2500ppm,2000 ppm respectively.For different micro channels,with Ni-Cr alloy surface as heat transfer surface,adding SDS?2000ppm?into R113 can improve the CHF of the vertical and horizontal micro channels about 39%-68%and37%-63%respectively.With CuO?1%?nano fluid modifying surface as heat transfer surface,adding SDS?2000ppm?into R113 can improve the CHF of the vertical and horizontal micro channels about 83%-139%and77%-131%respectively.The improvement increases with the decrease of length and the optimal width is 0.05mm.For the same micro channel,with CuO?1%?,Cu?0.75%?,Al₂O₃?1%?nano fluids modifying surfaces as heat transfer surfaces,adding SDS?2000ppm?into R113 can still improve the CHF of vertical micro channel.No matter modifying the heat transfer surfaces with nano fluids or adding SDS into deionized water or R113,the HTC can be both improved.There is a peak of the heat transfer coefficient value.At the peak,the improvement of HTC is greater than that of CHF.