Generation and Expulsion of Gas Rings within Liquid Film in Agitated Thin-Film Evaporator

Abstract

The agitated thin-film evaporator(ATFE) plays a crucial role in evaporation and concentration processes.The design of the scraper for processing high-viscosity non-Newtonian fluids in the ATFE is complex. The intricate scraping action of the scraper introduces gas into the liquid film, leading to the formation of a gas ring along the wall.This process subsequently reduces wall heat flow, thereby affecting heat transfer. Computational fluid dynamics(CFD) is used to simulate the flow field of the non-Newtonian fluid in the ATFE. The investigation focuses on understanding the mechanism behind the formation of gas rings in the liquid film and proposes methods to prevent their formation. The results demonstrate a transition of the gas from a gas ring suspended in the liquid to a gas ring attached to the wall after entering the liquid film. The scraping action around the circumference of the scraper helps to expel gas rings, indicating the necessity of adjusting the scraper arrangement and increasing the frequency of scraping to enhance gas ring expulsion. The spiral motion of the bow wave serves as the source of gas entry into the liquid film. Therefore, the rotation speed can appropriately increase to reduce the size of the bow wave, thereby inhibiting the formation of the gas ring from the source.This research investigates the mechanism of gas ring generation and expulsion, offering theoretical guidance for processing high-viscosity non-Newtonian materials in the flow field of the ATFE.

Keywords

agitated thin-film evaporator (ATFE) / non-Newtonian fluid / gas ring / high viscosity

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Funding

National Natural Science Foundation of China(51905089)

Fundamental Research Funds for the Central Universities,China(2232020D-31)