Design Aspect of Scraper Blade Assembly for Enhancing Film Heat Transfer Coefficient of Scraped Surface Heat Exchanger

Abstract

Scraped surface heat exchangers (SSHEs) are known for thermal processing of viscous food products. Heat transfer coefficient is one of the main parameter which influences the performance of processing liquid products in SSHE. The present study was undertaken to determine the film heat transfer coefficient for different blade assembly configurations. Milk was concentrated from 15 to 26% total solids using SSHE. Effect of number of blades (2, 4, 6), weight of blades (1.6, 1.75, 2.0 kg) and rotor speed (150, 175, 200 rpm) was investigated on scraped film heat transfer coefficient (h s ) using Response Surface Methodology. The results showed that h s increased linearly with increase in number of blades as well as rotor speed and that it was inversely related to blade weight. The h s varied from 695.3 to 1,415.4 W/m 2 K. The study was helpful in determining the design factors affecting film heat transfer coefficient of SSHE. PRACTICAL APPLICATIONSIn many of the earlier studies on SSHE, effect of scraper speed, flow rate or the number of blades has been individually studied. Therefore, effort was made to study the combined effect of these parameters. This article gives important insights on the design aspect of rotor blade assembly for thin film SSHE.