An experimental study on heat transfer and rewetting behavior of hot horizontal downward facing hot surface by mist jet impingement

Abstract

Heat transfer characteristics and rewetting behavior of 0.15 mm thick hot horizontal stainless-steel foil (SS-304) have been reported in the present paper during the mist jet impingement cooling from the bottom side through experimental investigation. The pneumatic internal mixing full cone mist nozzle (Lechler 136.134.xx.A2) with a spray angle 20° is used to develop a mist jet with a varied range of mist loading fraction (0.48–1.18). The initial surface temperature of the plate is maintained at 500 ± 10 °C with the help of an AC transformer. The present study uses an infrared thermal imaging camera (A655sc, FLIR system) to record the temperature of the hot foil. Various heat rewetting parameters namely, rewetting time, rewetting temperature and Peclet number are estimated from temperature data. The value of surface heat flux is found to be maximum at the stagnation point and found to gradually decrease in the radial direction away from the stagnation point, for different mist loading fractions. The non-dimensional rewetting velocity (Peclet number)) is found to decrease with the increase in the mist loading fraction. Correlations have been proposed to estimate maximum surface heat flux, rewetting temperature and Peclet number as a function of mist loading fraction and non-dimensional radial distance. © 2019 Elsevier Ltd