Measurement of temperature profile sing infrared thermal camera in turbulent stratified liquid flow for estimation of condensation heat transfer coefficients

Abstract

Direct-contact condensation experiments of atmospheric steam and steam/air mixture on subcooled water flowing co-currently in a rectangular channel are carried out using an infrared thermal camera system to develop a temperature measurement method. The inframetrics Model 760 Infrared Thermal Imaging Radiometer is used for the measurement of the temperature field of the water film for various flow conditions. The difference of temperature between at the center and near the side wall of rectangular channel at the same height measured by thermocouples is less than ±0.5℃. Therefore, the temperatures in the measured by the infrared thermal camera are calibrated by thermocouples. The bulk temperatures measured by thermocouples are almost the same as those by the infrared thermal camera. The local heat transfer coefficient is calculated using the bulk temperature profile. The developed method produces less local heat transfer coefficients than those estimated using the wall temperatures. It is found that the temperature radial profiles can be used to understand the interfacial condensation heat transfer characteristics. For all cases it is found that the temperature profiles are apt to be uniform. The tendency of the uniform temperature profile means the broad mixture layer of the temperature isothermal line near interface as the inlet water temperature increases. As the concentration of noncondensable gas increases. The temperature of the interface water layer becomes much less than the saturated temperature even though wave amplitude increases. Inclination angle has an important role in increasing wave amplitudes which increase the surface renewal rates.