NUMERICAL INVESTIGATION OF THE EFFECTS OF HEAT FLUX ON BUBBLE GROWTH AND DEPARTURE DURING NUCLEATE BOILING HEAT TRANSFER

Abstract

The demand to transfer higher heat fluxes at lower wall superheats and to predict the limits of the boiling process is growing and makes the scientific investigation of boiling phenomena inevitable. A numerical investigation on effect of heat flux on nucleate pool boiling heat transfer of water using five different heated surfaces such as: brass, copper, mild steel, stainless steel and aluminum were carried out at atmospheric pressure in this study. This present work is devoted to investigate the effects of heat flux on bubble growth and departure during a nucleate pool boiling of saturated water at 100℃ and 1 atmospheric pressure. All of the samples were tested under the same operational condition and surface temperatures were measured for each of the surface at different heat flux. The samples were heated under the same range of heat flux of 100 to 1000 kW/m2 and the corresponding coefficient of heat transfer was determined. It is found that the bubble diameter and heat transfer coefficient increase with increasing heat flux and temperature difference. It is also observed that the enhancement was found to be more pronounced at high heat fluxes. Copper has the best thermal performance among the samples and mild steel the least. The result revealed that among the heated surface tested in this study, copper and aluminium gave the best thermal performance at high and low superheated temperature condition respectively. Also, the heat transfer coefficients results obtained with the Computational Fluid Dynamics simulation method were compared with the experimental results for different pool boiling conditions obtained by other authors from the open literature.