Computational prediction of pressure drop and heat transfer with cryogen based nanofluids to be used in micro-heat exchangers

Abstract

Micro heat exchangers are the integral part of advanced technologies such as space technologies. However, the cooling of these micro heat exchangers encounters various challenges due to large aspect ratios. Further, the conventional coolants could not dissipate the heat due to limited thermal conductivity and specific heat. Hence, suspension of nanoparticles in such coolants would increase the efficiency of micro heat exchanges. Nanofluids are widely used in biomedical applications, as coolants in transportation, industrial cooling, nuclear reactor cooling and defense applications due to their higher stability, higher heat transfer capabilities and reduced particle clogging.In the present work, the thermophysical properties of Al2O3, SiO2, SiC, CuO and TiO2 nanoparticles in Liquid Nitrogen (LN2) are studied with the volume concentration of 3%. It is observed that thermal conductivity of nanofluid is enhancing with the increase in volume concentration of nanoparticles which result in enhancing the heat transfer rate in micro heat exchangers. In order to confirm this fact, a computational investigation on pressure drop and heat transfer is performed with Liquid Nitrogen as a base fluid and CuO, SiO2, SiC, Al2O3 and TiO2 as nanoparticles. A computational geometry is developed in ANSYS® and the pressure drop and heat transfer analysis is done using FLUENT®. Relevant boundary conditions are applied to reflect the practical operating conditions of micro heat exchangers. It is observed from the results that the decrease in pressures drop with the suspension of CuO nanoparticle is low. Further, the heat transfer is observed to be increasing with the addition of Al2O3 and SiO2 nanoparticles with the concentration of 3% by volume. Finally, it can be concluded that the dispersion of the nanoparticles in Liquid Nitrogen (LN2) is beneficial to be used in micro heat exchangers.