Experimental Investigation of Nucleate Boiling Over Enhanced Cylindrical Surface

Abstract

In the era of technological advancement, there are demands of devices which have high heat flux, high precision and should occupy as minimum space as possible. To keep these devices in best performing conditions, air-based cooling systems and single phase liquid cooling systems, whose practical cooling capacity is limited to few hundred W/cm2 is not sufficient. For such devices we need two phase liquid cooling system whose capacity is several thousand W/cm2 . Therefore, boiling is most preferred mechanism for the same. This mechanism is found in industrial applications of refrigeration, electronic chip cooling, power plants and so on. The boiling mechanism is divided into 4 regime, out of which nucleate boiling regime is the most efficient. The effectiveness of boiling is governed by Heat Transfer Coefficient (HTC) and Critical Heat Flux (CHF) which in turn are governed by bubble dynamics which includes bubble nucleation, its growth and deattachment from the heater surface. Worldwide experimental and numerical research is going on to enhance heat transfer using techniques such as active technique, passive technique and compound technique. The aim of the present project work is to carry-out the experimental investigation of pool boiling over the different micro-channeled cylindrical copper surfaces with R141b as working fluid under atmospheric conditions, on an already validated experimental setup. In order to ensure the repeatability of results, experiments were conducted twice on each piece for each pressure. Also, comparison of heat transfer performance was done using refrigerant R-123 in addition to R141b. Moreover, the experiments were done at different pressures. The results are in good agreement with the previous studies conducted on enhanced cylindrical surfaces.