Hydrodynamic and thermal performance analysis of an inclined anchor impeller designed for yield stress food mixing applications.

Mechanical agitation and mixing operations are basic processes in many industrial activities, especially in food industry. Agitation of food products with a non-Newtonian yield stress fluid and/or with a high viscosity is a common operation where standard anchor impellers are usually implemented to scrape the lateral surface of the tank. The flow generated by this type of impellers is predominantly tangential, particularly with the presence of Bingham fluids. In this regard, the present research gives a numerical investigation of the laminar flow and heat transfer of a Bingham fluid in a mechanically agitated tank equipped with an inclined anchors configuration, including the standard case. This configuration is intended for the enhancement of the axial flows specifically in the lower part of tanks, while keeping the main operation of scraping. Moreover, for heating process, the agitated system is equipped with a lateral jacket system where the temperature remains constant over time. The effects of the Bingham and Richardson numbers as well as of the anchor inclination angle are analyzed on the hydrodynamic and thermal stats. The differential balances that govern the studied phenomenon including continuity, momentum and energy equations are solved by the use of Galerkin finite element method. The results demonstrate the hydrodynamic, energetic, and thermal benefits of agitating yield stress fluids using an inclined base anchor. Indeed, significant axial hydrodynamic generation is observed with a reduced energy consumption of approximately 30% compared to the standard anchor, particularly at moderate rotational speeds. Furthermore, it enhances thermal insulation inside the mixing system and hence promoting heating process, especially in the presence of Bingham fluid and buoyancy force. [ABSTRACT FROM AUTHOR]