The miniaturization trend of transistors and increase in packing density of electronic devices has resulted in high heat flux generation, which has created a need for efficient heat removal systems. The present research is an experimental study of pool boiling using plain copper chip and microchannel chip with boiling surface of 34.5mm x 32mm. Three dielectric fluids, Perfluoro-2-methylpentane (PP1), perfluoro-methyl-cyclopentane (PP1C), and fluorocarbon (FC-87) were used in a closed loop pool boiling system to determine their performance at atmospheric pressure. The pool boiling results have been compared with literature for a boiling surface of 10 mm x 10 mm to study the effect of heater size.
To improve the performance of the pool boiling system, we desire high critical heat flux and low surface temperatures. In the current study, we introduced two external structures fitted on the test surfaces for regulating the flow of vapor through specific structures and generating independent liquid-vapor pathways without any deposition and/or chemical surface modifications of the test surface. Firstly, an array of hollow conical structures (HCS) called volcano manifold are printed using additive manufacturing technique. A critical heat flux (CHF) of 28.1 W/cm2, 38.3 W/cm2 and 32.5 W/cm2 was achieved for volcano manifold with plain copper chip using PP1, PP1C and FC87 respectively giving 19%, 33% and 6.5% enhancement in CHF respectively as compared to a plain chip without volcano manifold. Secondly, dual taper manifold having taper angle of 15° is printed using a stereolithography (SLA) additive manufacturing technique. Plain chip with dual taper manifold gave the CHF of 25.6 W/cm2, 31.7 W/cm2 and 32.3 W/cm2 for PP1, PP1C and FC-87, respectively. These results indicate a deterioration in CHF caused by vapor constriction. In addition, the heater size effect was studied by comparing the pool boiling performance of a plain copper boiling surface of 34.5 mm x 32 mm (Large heater) with 10 mm x 10 mm (Small heater) from published literature for all three refrigerants. It was noted that 31%, 66% and 104% increment in maximum heat transfer coefficient was obtained for PP1, PP1C and FC-87 respectively with larger heater over smaller heater at CHF. The geometrical parameters of the enhancement structures were based on published results for water. The results show that the external surface modification techniques require further geometrical parameter optimization as the current designs based on water performance caused vapor constriction effects that caused performance deterioration for dielectric fluids.
Mechanical Engineering (MS)
Department, Program, or Center
Mechanical Engineering (KGCOE)
Satish G. Kandlikar
Mody, Farhan, "Evaluation of External Surface Modification Techniques to Enhance Pool Boiling of Dielectric Fluids" (2019). Thesis. Rochester Institute of Technology. Accessed from
RIT – Main Campus
Available for download on Thursday, November 26, 2020