Heat transfer characteristics of swirling impinging jets

Abstract

Impinging jets are used in a wide number of industrial cooling applications due to their high heat and mass transfer abilities. The current research is concerned with the effect of swirl on the heat transfer characteristics of jet impingement cooling. Two inserts were designed order to generate swirling flow. These two designs, ?Swirl Insert A? and ?Swirl Insert B?, were tested at various Reynolds numbers, between 8000 and 16000 inclusive, and at H/D=0.5 and 1. The jet was directed downwards onto a 25?m thick stainless steel foil which was ohmically heated. Images were recorded using a thermal imaging camera focused on the underside of the foil. These images were then analysed using Matlab and the Nusselt number profile was obtained. It was found that, while both swirl inserts establish an improvement in the heat transfer by comparison to that of a jet with no swirl, the ?Swirl Insert B? design performed better that the ?Swirl Insert A? design for high Reynolds number at H/D=0.5 and consistently for H/D=1. It was also discovered that, while both the ?No Insert? and ?Swirl Insert B? results did not change dramatically with an alteration in H/D, ?Swirl Insert A? decreased by ~10%.