Investigation of the Entropy Generation and Exergy Destruction Rates for a Novel Micro-Jet Heat Sink Working With a Nanofluid for Efficient Cooling of Motor Inverters in Electric Vehicles

Abstract

Abstract Unlike the first law analysis which quantifies energy in systems, the second law of thermodynamics specifies the quality of energy and the direction of the processes. In this research, a novel heat sink based on micro-jet impingement for cooling inverters in electric vehicles is thermodynamically analyzed to establish the entropy generation and exergy destruction rates. The numerical simulations are performed using the finite volume method implemented in ANSYS Fluent. Numerical analyses are performed for typical motor inverter heat fluxes ranging from 100 to 300 W/cm2, Reynolds number between 5,000 and 20,000. Alumina-water nanofluid was considered with nanoparticles at concentrations of 0, 0.008, and 0.017 by volume. Results indicate that the maximum reduction in the thermal entropy generation rate is 6.65% when the nanoparticle concentration rises to 0.017. Whereas the frictional entropy generation rate increases by 73% for the same increase in nanoparticle volume fraction. Despite this, the total irreversibility drops as the concentration rises such that the highest reduction in the total irreversibility is 6.1% since the thermal entropy generation rate is the dominant source of irreversibility. With this, utilizing nanofluids decreases the exergy destruction rate leading to a lower amount of wasted energy. When the concentration is increased from 0 to 0.008 and 0 to 0.017 at a heat flux of 100 W/cm2, the optimal Reynolds numbers for maximum reduction in exergy destruction are 10,000 and 5,000, respectively.