Performance improvement of a falling-film-type heat exchanger by insertion of shafts with screw blade in a heat exchanger tube

Highly-efficient heat exchange is expected for the falling-film-type heat exchanger handled in this study by utilizing a falling liquid film, etc. The heat medium is flowed inside the heat exchanger tube. In contrast, the falling film is flowed outside the heat exchanger tube, thereby exchanging heat. In the previous study, considering the basic heat transfer characteristic of the falling-film-type heat exchanger, the design equation was developed in the limited extent. In this study, focusing on the flow condition in a heat exchanger tube of the falling-film-type heat exchanger, various shafts with screw blade were inserted in a single heat exchanger tube and it was evaluated how the pitch and height of screw and the flow rate of cooling water would give an effect on the heat exchange performance. Additionally, the heat transfer coefficient and the overall heat transfer coefficient of the falling-film-type heat exchanger were logically calculated, and then a theoretical value and an experimental value were compared and evaluated. As a result, it was clarified that the heat exchange performance of the falling-film-type heat exchanger was improved by inserting the shaft with screw blade, and theoretical and experimental values were roughly matched.