Studies on Heat Transfer and Pressure Drop Characteristics of Nanofluids in Flat Vertical Tubes

Abstract

Cooling is one of the critical problems being faced by the modern industry due to the technological development such as microelectronic devices, high power engines, and ultrahigh heat-flux optical devices. Conventional heat transfer fluids such as water and ethylene glycol have been used for cooling purposes in automobile radiators; however, the heat transfer performance of these liquids is limited owing to their poor thermo-physical properties. An enhancement in the heat transfer performance of these fluids can result in improved performance of the automobile engines. Nanofluids can be used in heat exchangers and automobile cooling systems due to their better features than micrometer and millimeter sized particles i.e., high specific surface area, less erosion of components, low pumping power, etc. In this work two types of nanoparticles such as aluminum oxide (Al2O3) and copper oxide (CuO) were used to prepare the nanofluids. The objective of the work is estimation of thermo physical properties of different concentrations of Al2O3 and CuO nanoparticles at different temperatures. The various thermophysical properties of prepared nanofluids such as thermal conductivity, density, specific heat and viscosity were measured experimentally using KD2 Pro, specific gravity bottle, differential scanning calorimeter and viscometer, respectively. The stability of nanofluids is checked by Zeta potential, measuring the absorbance using UV-vis spectrophotometer and thermal conductivity. The aluminum oxide nanofluids remain more stable than copper oxide nanofluids. The thermal conductivity enhanced significantly with increase in particle concentration and temperature. The thermal conductivity of nanofluids was more sensitive to temperature than that of the base fluid. The density and viscosity increased with increasing the particle concentration, while they both decreased with increase in temperature. The heat capacity of nanofluids increases with temperature but diminishes with increase in particle volume concentration.