Basic Study On The Thermosyphon Boiling Heat Transfer Of Three-dimensional Microchannel

In this paper,a new thchnology for 3D chip cooling is proposed to utilize the micro channels between chips to form the thermosiphon heat pipe,and a series of experiments were conducted to investigate the heat transfer characteristics.With deionized water and R113 as the basic heat-exchange working fluid,Ni-Cr alloy as the heating surface to simulates 3D chips,the influence of micro-channel three-dimensional size,tilt angle,working substance properties and heating surface treatment to thermosyphon boiling CHF and HTC were studied,and Two methods to enhance the thermosyphon boiling heat transfer of microchannels were proposed.Micro channels with the length of 30 mm,60mm,100 mm,the thickness of 0.05 mm,0.1mm,the width of 4mm,2mm,1.33 mm,1mm,0.8mm were used.Based on the experimental results of pure working fluid,the empirical formula for the thermosyphon boiling of conventional size channels was modified to make it suitable for the thermosyphon boiling of three-dimensional micro channels,which complements the effect of microchannel width on CHF.The error between the modified formula and experimental results is within 30%.In order to enhance the heat transfer,2000 ppm of surfactant SDS was added to the pure working fluid to form a moist fluid,thereby reducing the surface tension,enhancing the wettability,increasing the capillary force,and reducing the surface energy between the heating surface and the liquid surface.With the increase of the width of the channel,the enhancement rate of CHF decreases gradually;the longer the length of the microchannel with the same width and thickness,the weaker the enhancement;the smaller the thickness of the microchannel,the stronger the enhancement.For the moist R113,the CHF enhancement rate is 115% to 164%;for the moist deionized water,it is 117% to 156%.On the other hand,CuO nanofluids were used to modify the surface of the heating surface,a porous nano-deposition layer was formed,which increased the surface wettability of the heating surface,reduced the solid-liquid contact angle,and increased the vaporization core density.The CHF was enhanced,and the enhancement rate decreased with the increase of the channel length,and increased with the decrease of the channel thickness,but was insensitive to the change of the width of the three-dimensional microchannel.For R113,the CHF enhancement rate is 122% to 177%;for deionized water,it is 115% to 162%.While using the two kinds of enhancing methods at the same time,CHF was further enhanced.For the moist R113 with nano-structured surface,CHF enhancement rate is 132% to 224%;for moist deionized water with nano-structured surface,it is 135% to 208%.