S083032 Study on effect of natural convection to forced convection heat transfer m horizontal duct with hot bottom

Abstract

Heat transfer to the upper air flow from the lower hot water in a horizontal flow path is promoted by the influence of natural convection and evaporation. In the previous study, the correlation equation was obtained by experiment as the sum of the convective heat transfer and evaporation heat transfer. However, there is a question on the convective heat transfer, which was much larger than the calculated value. In this study, therefore, experiment was done using the flow channel made of acrylic resin with 100 mm height, 600 mm length and 50 mm width The heat transfer area on the bottom of the flow channel was 300 mm length and 50mm width. Air velocity in the flow channel was 0.164 〜 1.02 m/s and average temperature of the heat transfer surface was 313 and 353 K. Temperature distributions of air flow and the heat transfer surface were measured by thermocouples and a radiation thermometer, respectively. The measured heat transfer was compared with the value calculated by a correlation for forced convection and heat transfer enhancement due to natural convection was studied.