Influence of Porous Oxide Layer on Water Spray Cooling

- Steel production and processing are connected with the formation of an oxide layer on a hot surface of steel. The oxide layer influences cooling and the final quality of the steel. Spray cooling is mainly influenced by water impingement density and by surface temperature, but the influence of the oxide layer is not negligible. The oxide layer can be considerably porous. The porosity of the oxide layer significantly influences its thermal conductivity, because air pores have much lower thermal conductivity compared to pure oxides. In this paper, the influence of the oxide layer on water spray cooling is experimentally and numerically investigated. The heat transfer coefficient of an oxidized steel surface and a clean steel surface are compared and the effect of the oxide layer on the Leidenfrost temperature is studied. Also, the porosity of the oxide layer and the average thermal conductivity of the porous oxide layer are determined for different oxidation regimes.