Numerical Study of Convective Heat Transfer Performance, Entropy Generation and Energy Efficiency of Al and Al_2O_3 Nanofluids in Minichannel

摘要

Due to their enhanced thermophysical properties, nanofluids are considered a promising cooling solution in many applications including energy systems and electronics. The convective heat transfer (CHT) characteristics and entropy generation of ethylene glycol (EG)/water-based Al and Al_2O_3 nanofluids are numerically investigated for five nanoparticles concentrations (from 1.0 to 3.0 vol.) and Reynolds number ranges between 400 and 2000 (laminar flow) under constant heat flux conditions in a minichannel. CFD tools are used to develop the numerical approach which is validated using experimental data of the base fluid. The results show good enhancement in CHT for both nanofluids in comparison with the base fluid and the CHT rises with increasing nanoparticles concentration and reaches the maximum enhancements of 20.3 for Al nanoparticles and 25.1 for Al_2O_3 nanoparticles at 3.0 vol. concentration. The pressure drop also increases with increasing nanoparticles concentration and Re for both nanofluids, while friction factor is increased with increasing concentration of nanoparticles and reduced with the increase of Reynolds number. The results of entropy generation showed a decrease with increasing the nanoparticles' concentration with lower values for Al nanofluids than Al_2O_3 nanofluids. In another hand, the energy efficiency evaluation of the nanofluids performance flow through the heat transfer system shows that there is no considerable change in the used energy of the overall system with nanofluids due to the increase in the pumping power.