Experimental Investigation of Heat Transfer Coefficient of Nanofluid Flow Boiling in a Horizontal Annular Tube

Abstract

Nanofluid is a suspension of nanometer-sized particles in a base fluid. In the last newlinedecade, nanofluids are in research focus to improve the efficiency of thermal systems. In the newlinepast few years, the flow boiling of nanofluids has achieved a lot of attention. When the liquid newlineis forced to flow over a heated surface and the phase transition from the liquid to the gas takes newlineplace is termed as the flow boiling. Flow boiling of nanofluids is a difficult process to newlineunderstand and still needs more research. Due to this complexity nanofluids are considered to newlinebe exceptionally attractive heat transfer fluids in numerous thermal applications. In the flow newlineboiling bubbles are present which develop and collapse quickly close to the surface. Flow newlineboiling is affected by mass flux, heat flux, and the pressure in the test section. newlineIn this study, experimental investigations have been performed on the flow boiling of newlineDI (de-ionized) water, water-based TiO2, and Al2O3 nanofluids flowing in an annular tube to newlineexamine the heat transfer coefficient. An Ultrasonic Vibration Machine (UVM) was used to newlineprepare the nanofluids. During the experiments, the volumetric concentration of both the newlinenanofluids was varied from 0.05 to 0.20%. The process parameters i.e. heat flux, mass flux, newlineand pressure were varied from 6.25 to 143.2 kWm newline-2 newline, 338 to 1014 kgm newline-2 newlines newline-1 newline, and 1 to 2.5 bar, newlinerespectively. From the results, it was observed that the heat transfer coefficient for both the newlinenanofluids was greater than water. newline