Heat Transfer during Spray Cooling of Flat Surfaces with Water at Large Reynolds Numbers

Abstract

We present a new Nusselt number correlation for spray cooling at large Reynolds numbers and high surface temperatures for water sprays impinging perpendicularly onto a flat plate. A large set of experimental data on spray cooling of hot surfaces with water has been analyzed, including the water temperature effects. For large-scale cooling, such as in industrial processes, large number of injection parameters such as number, type, pressure, and angle of the spray injection has led to a multitude of correlations that are difficult for general and practical applications. However, by synthesizing a set of experimental data where all of the above parameters have been varied, we find that the Nusselt number and therefore the heat transfer coefficient can be cast accurately as a function of the Reynolds number. Water is widely used as the coolant during spray cooling, and has a specific phase change characteristic. At large Reynolds number (Re > 100,000) and surface temperature (Ts > 600˚C) ranges, which are of interest in large-scale spray cooling, the effect of water temperature is quite significant as it affects the film boiling close to the surface. This effect also has been parameterized using experimental data.

Wise Choice of Showerhead Patterns: How to Save Energy during Showering While Maintaining Thermal Comfort

“…However, no specific effects for overall showerhead patterns were concluded since only one characteristic parameter of the water flow pattern-the nozzle area ratio-was considered in their study. Although the influence of spray patterns on the heat transfer coefficient was rarely studied during showering, it was investigated by many studies for the industrial spray cooling process [21,22]. Several parameters of spray patterns (such as spray pressure, water flux, and distribution of drop diameter) were examined to quantify their impacts on the heat transfer coefficient between water and metal surfaces [23,24].…”

A model of water-spray cooling effect on a continuous casting process

“…A new Nusselt number correlation for spray cooling at large Reynolds numbers and high surface temperatures for water sprays impinging perpendicularly onto a flat plate is presented in Hnizdil's et al research work [11]. A large set of experimental data on spray cooling of hot surfaces with water has been analysed, including the water temperature effects.…”