3D Transient Spray Cooling Heat Transfer Simulation for Metallic Slabs of Various Alloys

Water spray cooling is widely used in many industrial processes to control the surface dissipation of a material ported at high temperatures. To predict heat transfer and obtain the rate of required temperature distributions of the surface, it is necessary to understand the basic spray cooling dynamics and a more precise estimation of the heat transfer rate. This paper is about a three-dimensional simulation to estimate the transient heat transfer obtained locally by water spray to reduce the temperature of heated metal. The use of water spraying is a practical and flexible process. It is possible to vary, in space, time, and in large proportions the flux of extracted heat and controls the density of the flow of water which is a key element and very simple to achieve. Globally, the aim of this study is to simulate the spray cooling of different metal slabs for various alloys (steel, cast iron, titanium, nickel) by mainly comparing cooling in maps of iso-surfaces and in curves (at starts and globally) obtained after estimation of the heat flux.

Experimental Investigation on Heat Transfer of Water Spray Cooling by Addition of n-Butanol

Heat transfer characteristics of water spray cooling with n-butanol additive were experimentally studied in this paper. The results indicated that adding n-butanol can effectively enhance the heat dissipation and control the surface temperature. The optimal concentration of n-butanol corresponding to the best heat transfer performance is 0.5 vol%. The experimental Nusselt numbers also agree well with a previous correlation with Weber, Prandtl, Jacob and Reynolds numbers, evidenced by a maximum absolute error of 6.34%. The measurement also showed that the decrease of surface tension and contact angle of the n-butanol-water mixture is the main mechanism to enhance the spray cooling heat transfer, while other physical properties also play an important role. The surface temperature non-uniformity in the radial direction is more apparent at a high heat flux while the addition of different contents of n-butanol has a negligible effect.

Heat Transfers Coefficients of Directly and Indirectly Cooled Component Areas during Air-Water Spray Cooling

For the determination of heat transfer coefficients in air-water spray cooling, two methods are presented that are capable of characterizing multi-nozzle cooling set-ups. The methods are based on the quenching of thin-walled tubes or massive cylinders on which cooling curves are recorded at given positions with thermocouples. The temperature dependent heat transfer coefficients were calculated by an inverse calculation and the measured temperature-time-curves could be reproduced with these data in numerical cooling simulations. Next, the determined heat transfer coefficients were used for the calculation of an air-water-spray quenching process of a forging part with more challenging geometry. The calculated results were compared with thermocouple measurements. Different calculation variants for the heat transfer on component surfaces not directly exposed to the air-water spray are shown and discussed. ◼