Local and Instantaneous Heat Transfer Characteristics of Arrays of Pulsating Jets

Abstract

Recent investigations have revealed that pulsations in an incident jet flow can be an effective technique for modifying convective heat transfer characteristics. While these studies focused on single impinging jets, industrial applications of impinging jets usually involve arrays of jets. To explore the effects of flow pulsations on the heat transfer performance of jet arrays, an experimental investigation has been performed of instantaneous and time-averaged convective heat transfer to a square, in-line array of circular air jets within an unit cell of the array. Hot-film anemometry was used to document the jet flow field. Instantaneous and time-averaged convective heat transfer rates were measured using a heat flux microsensor. An ensemble averaging technique was used to separate the pulsating component of flow velocity and heat transfer from the turbulent components and thereby assess the effect of flow pulsation on turbulence intensity and heat transfer. For the ranges of parameters considered, results indicate convective heat transfer distributions become more uniform in response to pulsations but heat transfer is not enhanced. Improved uniformity can be a useful aspect in many jet applications.