Heat reversal phenomenon of spray cooling and its heat transfer enhancement characteristics

Abstract

Aiming at the requirements of the heat dissipation for high heat flux laser medium, an experimental platform was designed and built. The spray cooling of heat transfer enhancement experiment with different concentrations of sodium dodecyl sulfate aqueous solution as the working fluid was studied. The results show that within a specific range of heat flux density, as the heat flux density increases, the temperature of the heating surface does not rise but drops, which was named heat reversal. The heat reversal phenomenon increased the convective heat transfer coefficient by as much as 94.0%. The heat flux density range corresponding to heat reversal was 80−130 W/cm2, which had a weak relationship with concentration. This means that, in spray cooling, an increment in heat load can cause a temperature drop of the heated surface under certain circumstances. This phenomenon only occured when the heat flux density was gradually increasing, and it was not found in the process of reducing and adjusting the heat flux density. Surfactant boiling in the pool will also cause thermal reversal, but the specific reason remains to be studied.