Experimental and Numerical Investigations on Steady and Unsteady Jet Impingement Cooling for High-Power Electronics

Effective cooling of electronic equipment has emerged as a challenging and constraining problem of the 21st century. This paper reports the experimental and numerical investigations carried out to study the feasibility and effectiveness of steady and unsteady air jet impingement cooling used in high-power electronics. The results obtained from numerical studies are validated with the values obtained from experimental studies. Studies have been conducted to see the effects of parameters such as the Reynolds number, the period of pulse, and the ratio of jet spacing to diameter (Z/D) on the heat transfer characteristics. The Reynolds number is varied between 10000 and 20000 and the period of pulse is varied between 2 and 10 s. It is found that in both steady and unsteady jets, an optimum cooling is obtained when the Z/D ratio is 5. For a Reynolds of 20000, the stagnation heat transfer coefficient increases by 25% when an unsteady jet is used instead of a steady jet. A correlation is proposed for the Nusselt number in terms of the Reynolds number and this is valid for air as the cooling medium.