The heat transfer from hot water flow to cold air flow that has two terms of convection and evaporation was examined mainly focusing on the convective heat transfer. When the flow was laminar, the large effect of natural convection was observed and the heat transfer was considerably enhanced. However, when the flow was turbulent, the convection heat transfer was little enhanced. It has been reported that the convection heat transfer is greatly enhanced even in the turbulent condition. Further examination is required.