INVESTIGATION INTO METHODS OF ENHANCING HEAT TRANSFER UNDER IMPINGING AIR JETS

Impinging air jets are widely used in industry, for heating, cooling, drying, etc., because of the high heat transfer rates which are developed in the impingement region. In this study, two methods of enhancing jet heat transfer have been investigated, namely, by using turbulence promoters to artificially raise the turbulence level, and by using a loudspeaker to excite the jet acoustically. In both these cases, the increases in heat transfer from enhancement were found to be modest. Some experimental hot-wire anemometry data obtained for free and impinging air jet flows are presented here. The existence of a relationship between turbulence intensity and heat transfer mechanism is also discussed.