ENHANCEMENT EVALUATION CRITERIA FOR POOL BOILING ENHANCEMENT STRUCTURES IN ELECTRONICS COOLING: CHF ENHANCEMENT RATIO (ER-CHF) AND ENHANCEMENT INDEX (EI)

Extensive research shows the necessity of efficient cooling systems to enable electronic components to operate at high performance levels for a sustained period. While conventional methods have served the cooling needs so far, rising computational power, energy efficiency, and sustainability requirements call for improved techniques. The literature shows the effectiveness of two-phase systems in cooling electronic components like microprocessors. The literature further describes various enhancement mechanisms to elevate the critical heat flux (CHF) and heat transfer coefficient (HTC) in these systems. While a high CHF is desired, having a high HTC is equally important to keep the operating temperatures below a permissible limit. The present article summarizes enhancement structures found in the literature suitable for electronic cooling to provide this dual enhancement in CHF and HTC. New enhancement evaluation criteria that also consider the surface temperature limit imposed by the electronic components are introduced. The CHF enhancement ratio (ER_CHF) represents the ratio of CHF for enhancement structures to the CHF for a plain surface, and the enhancement index (EI) represents the ratio of wall superheat at CHF with the enhanced structures to the wall superheat at its respective CHF condition for a plain surface. It is desirable to have a high value of ER_CHF coupled with a low value of EI (lower the better), preferably below 1.0.