Flow pattern and heat transfer in agitated thin film dryer

The design of agitated thin film dryer (ATFD) is difficult both mechanically and process engineering point of view. The present work describes the basic flow pattern in ATFD in terms of bow wave and its transformation along the dryer height. The effect of flow rate, jacket side heating medium temperature and speed of the rotor has been studied for a pilot scale ATFD. The effect of rotor speed was found less significant for water as a feed material than for sugar and ammonium sulfate solutions over the studied range of speed. The scraped side heat transfer coefficient was obtained using the penetration theory and its value was found in the range of 3000–7000 W/m2 °C.

► Design of agitated thin film dryer.
► Penetration theory is used to model heat transfer in ATFD.
► Scraped side HTC is determined.