This paper focuses on the existence of the two-phase zone and the dry-out condition at a heated porous surface. The work is relevant to high intensity drying processes, underground coal gasification, geothermal energy production from hot dry rock, and around nuclear waste repositories. The condition for which a two-phase zone does not exist due to high heat flux is examined experimentally and theoretically. The results indicate that when the applied heat flux increases, the two-phase zone becomes smaller. In addition the dry-out condition is determined to be approximately 135 kW/m(2). (C) 2012 Elsevier Ltd. All rights reserved.