Heat Transfer Dynamics in Scraped Surface Heat Exchangers

Scraped surface heat exchangers employ mechanically actuated blades to continuously remove adherent layers of fluid or semi-solid material from the internal heat transfer surface, maintaining thin films and preventing fouling. This dynamic scraping action enhances turbulence, renews the thermal boundary layer and thereby fosters elevated convective heat transfer coefficients even in highly viscous or phase-changing fluids. The geometry of the rotor–stator assembly, scraper speed and clearance gap dictate the thickness of the product film and the intensity of shear-induced mixing. Rheological characteristics, including non-Newtonian viscosity, influence local flow regimes and heat diffusion. Mathematical models range from analytical solutions for idealised laminar flows with temperature-dependent viscosity to detailed computational fluid dynamics simulations that resolve recirculation zones and transient thermal fields. Dimensionless groups such as the Reynolds, Prandtl and Nusselt numbers enable correlation of performance across scales. Industrial applications span food and dairy processing, ice-cream freezing, polymer melting, chemical crystallisation and pharmaceutical manufacturing. The global significance of this technology arises from its ability to process viscous, sticky or particulate-laden fluids under continuous operation with improved energy efficiency and product quality.

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Heat Transfer Dynamics in Scraped Surface Heat Exchangers publication trend

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Technical terms

Scraped surface heat exchanger (SSHE): A heat exchange device in which rotating or reciprocating blades continuously remove material from the heat transfer surface to enhance heat transfer and prevent fouling.

Heat transfer coefficient: A measure of the convective heat transfer rate per unit area per unit temperature difference between a solid surface and a fluid.

Rheology: The study of flow and deformation behaviour of fluids, especially those exhibiting non-Newtonian properties.

Computational fluid dynamics (CFD): A numerical simulation technique used to analyse fluid flow and heat transfer by solving governing equations on a computational grid.

Nusselt number: A dimensionless group expressing the ratio of convective to conductive heat transfer across a fluid boundary layer.

References

1. MHD and heat transfer analyses of a fluid flow through scraped surface heat exchanger by analytical solver. AIP Advances (2019).
2. Performance evaluation and CFD investigation of scraped surface ice cream freezer augmented with LN2 freezing technique. Cogent Engineering (2024).
3. Intensification of thermal and rheological processes in a scraped-surface apparatus. Foods and Raw Materials (2018).