Evaluation and prediction of overall heat transfer coefficient of Scraped surface heat exchanger during kheer making

Abstract

Scraped surface heat exchanger (SSHE) is one of the adaptable equipments for products which are viscous, containing suspended constituents which tend to deposit and form layer on the heat transfer surface. The study was undertaken to evaluate and predict the overall heat transfer coefficient (U) of SSHE for making kheer. The performance of the developed SSHE was evaluated at three different steam pressures (1.0, 1.5 and 2.0 kg/cm2), scraper speeds (10, 20 and 30 rpm) and batch sizes (10, 15 and 20 kg) during kheer making. There was significant increase in the U-value with increase in operating steam pressures, batch sizes and scraper speeds. The quality of the kheer prepared in SSHE at optimized condition (i.e. 1 kg/cm2 steam pressure, 20 kg batch size and 30 rpm scraper speed) was found superior in terms of the sensory attributes, having U-value of 1197.40 W/m2K, steam side heat transfer coefficient (ho) was 8634.60 W/m2K and product side heat transfer coefficient (hi) was 2251.53 W/m2K. The regression equation was developed for predicting the U-value.