The role of exothermic reaction in the enhancement of high mass flux spray cooling

Abstract

Considerable reduction of vapour layer on the hot substrate is the main requirement during the process of ultrafast cooling of metals and this cannot be achieved by implementing the conventional cooling methodologies. Therefore, in the current work, an attempt has been made to reduce the vapour layer effect by using Na2CO3 as the additive in case of high mass flux spray cooling. The heat transfer analysis depicts augmentation and the maximum heat flux of 1.72 MW/m2 is achieved in case of water spray with 50 g Na2CO3. The increment in latent heat extraction period due to the exothermic reaction between sodium carbonate and water, alteration in vapour bubble coalescence rate by the released CO2 after reaction and shifting of thermo-physical properties in the positive direction of heat transfer are the key reasons behind the heat transfer enhancement. In addition to the above, the dropwise evaporative cooling experiments were conducted to reveal and support the heat transfer mechanism more clearly. The variation in Nu, Pr and Bg clearly ensures the augmentation in heat transfer rate. Finally, the effect of Na2CO3 on the surface morphology of the steel plate and the corrosive nature are identified by conducting SEM analysis and corrosion test, respectively.