STUDY OF MULTISPECIES NANO-PARTICLES TO ENHANCE THERMO-HYDRAULIC PERFORMANCE IN MICROCHANNELS

Abstract

Nanofluid is the colloidal suspension of nano-sized solid particles of metals or metal oxides in base fluids such as water, ethylene glycol etc. When liquid is mixed with nanoparticles, it exhibits substantially higher thermal conductivity than those of the corresponding base fluids. The augmented thermal conductivity of nanofluids over the base fluids is considered one of the driving factors for enhanced heat transfer performance of nano-fluids. The forced convection heat transfer of nanofluid is investigated by numerous researchers over the last few years. Recently, multispecies nanofluids have been defined as a new class of nanofluids with possible applications in almost all fields of heat transfer. The idea of using multispecies nano-fluids is expected to improve the heat transfer characteristics of individual nanofluids and to beneficially combine different properties from metal oxides, metals etc. The present research work is undertaken using the Computational Fluid Dynamics (CFD) to analysis and assess the high performing nanofluid for micro-channel applications. The study considers three metal oxide, two metal nano particles and their combinations in the base fluid i.e. desalinated water. The study is conducted for different Reynolds numbers and heat capacity. The performance of the nano-fluids is assessed based on the convective heat transfer coefficient, Nusselt number and pumping power requirement based on total pressure loss. The extensive numerical analysis suggests that MgO-Water nano-fluid possesses excellent heat transfer performance over other combinations considered. Study also reveals that the metal oxides possess better cooling performance in terms of convective heat transfer coefficient as compared to metal nanofluids. Among multispecies nanofluids of Ag-MgO-Water, Al2O3-Cu-Water and CuO-Cu-Water, the Al2O3-Cu-Water nano fluid performed better providing highest Nusselt number which is approximately 6% over and above that provided by pure water. Utilizing the data generated by parametric study for different nano-fluids, two combinations nanofluids are utilized for design of a compact heat exchanger with three different heat capacities i.e. 1 kW, 50kW and 100 kW. The hydraulic performance of this heat exchanger was compared in terms of pumping power requirements and it revealed that pumping power requirement increases nearly exponentially for higher Reynolds numbers.