SIMULATION OF NUCLEATE POOL BOILING HEAT TRANSFER CHARACTERISTICS OF THE AQUEOUS KAOLIN AND BAUXITE NANOFLUIDS

Nanofluid suspensions have become the working fluid of the nowadays' heat transfer implementations due to their distinguished behaviors in convective heat transfer. Boiling heat transfer which provides high heat fluxes is a kind of convective heat transfer, and thereby, thermal performance of such mechanism largely depends on the type of working fluid utilized. In this study, heat transfer characteristics of two different aqueous nanofluid suspensions, namely, kaolin-distilled water and bauxite-distilled water, under saturated boiling conditions were investigated numerically. Using computational fluid dynamics (CFD) approach and time-dependent volume-of-fluid (VOF) multiphase model, vapor volume fractions and velocity vectors in fluids of interest were specified in both distilled water and the prepared nanofluid suspensions. For each working fluid, the beginning time of boiling was determined to illustrate how nanoparticles affect this phenomenon. Besides, the influences of the heating power applied to the heater on such boiling characteristics as bubble shape, bubble generation, and the quantity of bubbles were investigated. The boiling regimes of transition boiling and film boiling that cannot be encountered in operation were demonstrated by numerical simulations. The numerical results show that nanoparticles doped into the distilled water decreased the beginning time of the boiling compared to distilled water, and remarkably affected the bubble generation and departure characteristics.