Influence of pressure and surface roughness on the heat transfer efficiency during water spray quenching of 6082 aluminum alloy

The heat flux (q) and heat transfer coefficient (h) at the interface between hot aluminum surface and spray water were determined by using an inverse heat conduction method. Good agreements between numerically calculated temperatures with the inverse identified h and experimentally measurements demonstrate that the method is valid for solving the q and h of spray quenching process. The estimated heat flux consists of three main stages of transition boiling, nucleate boiling and single-phase cooling. The results show that both the heat flux and heat transfer coefficient increase with the increasing of spray pressure. When the surface temperature is lower than 170 °C, the q, h and the maximum heat transfer coefficient (hmax) decrease and then increase as surface roughness increases. However, when the surface temperature is higher than 170 °C, the influence of surface is insignificant. This phenomenon may be attributed to the variation of nucleation site density with surface roughness.