CHARACTERISTICS OF WETTING TEMPERATURE DURING SPRAY COOLING

摘要

An experimental study has been done to elucidate the effects of mass flux and subcooling of liquid and thermal properties of solid on the wetting temperature during cooling of a hot block with spray. A water spray was impinged at one of the end surfaces of a cylindrical block initially heated at 400 or 500 deg C. The experimental condition was mass fluxes G velence 1 - 9 kg/m~(2) s and degrees of subcooling (DELTA)T_(sub) velence 20, 50, 80 K. Three blocks of copper, brass and carbon steel were prepared. During spray cooling internal block temperature distribution and sputtering sound pressure level were recorded and the surface temperature and heat flux were evaluated with 2D inverse heat conduction analysis. Cooling process on cooling curves is divided into four regimes categorized by change in a flow situation and the sound level. The wetting temperature defined as the wall temperature at a minimum heat flux point was measured over an extensive experimental range. The wetting wall temperature was correlated well with the parameter of G(DELTA)T_(sub). The wetting wall temperature increases as G(DELTA)T_(sub) increases and reaches a constant value depending on the material of the surface at higher region of G(DELTA)T_(sub).