Experimental Study on Control of an Impinging Jet Heat Transfer Using Triangular Tabs

Abstract

This paper describes the heat transfer enhancement by triangular tabs attached to the nozzle exit of the jet. Experiments on the impinging jet were performed to clarify the effect of the triangular tabs on the heat transfer. In particular, the attention is paid on the relationship between tab pitch angle θ and heat transfer enhancement ratio defined as Nu_Tab/Nu₀. Temperature distribution was measured by a thermosensitive liquid crystal sheet on the impingement plate of a glass coated by ITO (Indium Tin Oxide) film. In the case of θ =90 or 135 deg, the region of heat transfer enhancement is wider than the case of θ =45 deg. The velocity field was also measured by a hot-wire anemometer in the jet and over the impinging plate to investigate the relation between the flow field and the temperature field. It is found that the flow fluctuation by the tabs clearly contributes to the heat transfer promotion.