Heat transfer studies in a horizontal lobed channel

Due to the need for improved, efficient and effective heat transfer, design of heat exchange equipment is still a relevant topic for research. The current work presents investigation on the effect of lobed geometry on heat transfer, pressure drop and critical heat flux in comparison with a plain horizontal tube. The lobed channel is a novel passive technique to investigate for the heat transfer enhancement. Experiments have been performed on plain tubes as well as lobed channels, both made of SS304 to study the effect of this geometry on pressure drop, heat transfer and critical heat flux characteristics. R-123 was used as the working fluid in these experiments. Three different lengths of test section were used for both the geometries. In case of lobed channel, three different values of lobed depth were used. The local wall temperature was measured by thermal imaging technique which was then used to evaluate local heat transfer coefficient. The values of pressure drop and critical heat flux measured in the experiments were compared with different correlations both for subcooled and saturated region of flow boiling regions. The occurrence of critical heat flux for plain tube is found to be of departure from nucleate boiling (DNB) type and it increases with increase of mass flux. Performance on lobed channel shows the rise of critical heat flux for the same mass flow rate. As expected, this is associated with a pressure drop penalty. (author)