An Experimental Investigation of Pool Boiling Heat Transfer Over a Micro-finned Cylindrical Surfaces

Abstract

Pool boiling heat transfer provides an excellent mechanism for the removal of heat from the surface being heated. High heat transfer rates are achieved due to the phase change of liquid to vapour. Pool boiling is used in a variety of applications, such as power generation, electronic cooling, refrigeration, and air conditioning heat transfer devices. Over the past few decades, numerous studies have been conducted on the enhancement of pool boiling using different heat transfer enhancement techniques. The techniques can be divided into three categories: passive, active, and compound. In the present work, passive techniques have been used for the enhancement of the pool boiling over the cylindrical surfaces. The V-grooved microchannel has been formed over the cylindrical surface as part of the passive technique, and an experimental study was conducted on this surface using R123 at different pressures. The experiments were conducted on three MCFS between the heat flux ranges of 10kW/m2 to 110kW/m2 in decreasing order of heat flux, and the results of these three MFCS are compared to plain surface. The high density cartridge heater is used to supply heat to the cylindrical micro-finned surface. To obtain the wall superheat, K type thermocouples and RTD sensors have been used, respectively. The pressure during experiments were maintained by supplying the chilled water through the condenser coil. It is a well-known fact that the boiling heat transfer coefficient depends upon the bubble departure behaviour from the surface contact angle and fluid properties. In this work, the bubble departure diameter over MFCS is also studied. It is measured by Image-J software from images captured by using a Canon EOSI1200D camera at different values of heat fluxes at various pressures. The result indicates that the BHTC increases with pressure. There is a significant improvement in MFCSs in BHTC at all pressures. Out of all three MFCS’s, MFCS-3 with a hydrophobic surface (contact angle of 109.75°C) and having a high depth and low fin thickness, has better performance.