Review of Nucleate Pool Boiling Heat Transfer using Refrigerant

摘要

Nucleate pool boiling has an important place in refrigeration industries. The pool boiling process occurs in the shell side of flooded evaporators and low pressure refrigerants are proposed for industry applications. Enhancement of heat transfer rate depends on different design of heating surface, type of refrigerant and operating parameters like heating surface roughness, surface orientation, operating pressure & temperature. Refrigerant plays a crucial role in the study of nucleate pool boiling heat transfer. Various inferences have been drawn based on the existing parameters by different researchers for enhancement of heat transfer rate. In this paper a detailed study has been carried out using different refrigerants on different surfaces to investigate the optimum value of heat transfer coefficients (HTC). The process could be further investigated using heat transfer enhancement particles such as nanofluids and modification of the heating surface. The surfaces are characterized with contact angle, roughness, film thickness and scanning electron microscopy (SEM) & atomic force microscopy (AFM) etc. The surface modification can be done by nanocoating or polishing the surface area. The addition of lubricant to individual or binary or ternary refrigerants can significantly alter the boiling phenomena for accumulating lubricant at the nanocoating heat transfer surface. Many researchers explained the heat transfer enhancement techniques by the passive methods. Many authors gave empirical correlations (dimensional and nondimensional) for heat transfer coefficient in terms of surface roughness factor, vapour density, liquid density, etc from their experimental results. But there was no theoretical method to get the value of HTC which is a function of bubble density, surface roughness factor, bubble growth, etc.