Date of Award


Publication Type

Master Thesis

Degree Name



Mechanical, Automotive, and Materials Engineering


heat transfer, industry, inverter, jets, power electronics, turbulence


Ram Balachandar


Narayan Kar




With an increasing shift from the use of conventional internal combustion engine vehicles (ICE) to that of electric vehicles (EV), comes a great demand to improve the reliability and efficiency of on-board power electronics of an EV inverter. During typical operating conditions, heat fluxes up to 300 kW/m2 are common leading to SiC and GaN based switching elements to reach temperatures well above 175 ᵒC and causing them to fail. To this end, a thermal management system is required to cool the electronic components. Impinging jet technology is growing in popularity for electronics cooling applications due to its superior mass and heat transfer capabilities and is the cooling method investigated in this study. The working fluid studied is a 60 to 40% (by volume) ethylene glycol - water mixture. The jet plate included an in-line array of tapered impinging jets with a nozzle inlet and outlet diameter of 4 mm and 2 mm, respectively. The effects that Reynolds number, coolant inlet temperature, stand-off distance (H/D) and jet to jet spacing (S/D) have on the overall efficiency of the system is studied. The overall cooling efficacy is determined based on the heat transfer to pressure drop trade-off. The jet Reynolds numbers tested were 3,398, 5,112, 7,973 and 10,592. A small, intermediate and large stand-off distance of 2, 5 and 8, respectively were analyzed. For each stand-off distance, a small and large jet-to-jet spacing of 6 and 18.5 were tested. It was found that small jet-to-jet spacings and large stand-off distance is detrimental to the cooling performance of the system. It was also determined that small stand-off distances result in the highest pressure drops and large stand-off distances reduced the heat transfer performance due to lower jet velocities contributed by the entrainment effect. This is the first study to be conducted towards the use of impinging jets to cool inverters.