Examination of the Local and Fluctuating Heat Transfer due to Swirling Jets Impinging upon a Heated Horizontal Surface

Abstract

In the area of heat dissipation, impinging jets have been researched over many years and are a well defined method of attaining high heat transfer coefficients. Many different techniques have been looked at over past years in an attempt to discover a way to enhance this heat transfer further. This study investigates the effect of introducing a swirling motion into the fluid flow before exiting a jet nozzle. The final objective is to discover an optimal swirl geometry which will increase the heat transfer within a system compared to what would be achieved from a non-swirling jet with the same external nozzle geometry. The impinging jets’ performance is determined through experimental testing using thermal imaging techniques and hot film sensors with high response times. Results from comparing the heat transfer distributions of the non-swirling jet to four swirling jet geometries have shown both enhanced and diminished performance. The changes in the Nusselt number distributions are found to be highly dependant on the swirl generator geometries. The fluctuating heat transfer results provided by a hot film sensor have illustrated the regions where the swirl generators influence the heat transfer.