An experimental study on the heat transfer performance in a batch scraped surface heat exchanger under a turbulent flow regime

Abstract

Heat transfer during scraping of the thermal boundary layer is a commonly encountered phenomenon. The most notable device where scraping heat transfer occurs inherently is a Scraped Surface Heat Exchanger (SSHE), which is widely used in the chemical and food industries. The present study involves an experimental heat transfer investigation into an SSHE operating in a batch mode. The main goal of this research is to investigate the impact of the scraping effect on heat transfer. We examined the influence of the rotational speed of the scrapers, blade-to-wall gap width and the type of gaseous working fluid on the heat transfer process. The obtained results of the heat flux and heat transfer coefficient are in the range of 500÷1500W/m2 and 20÷45W/(m2K), respectively. Experimental results show a linear dependence of the heat flux and heat transfer coefficient on rotational speed in a turbulent regime. Based on the experimental results, non-dimensional correlation for the Nusselt number is proposed as Nu=1.765Rer0.496Pr0.33. The comparison with the mathematical models and experimental correlations available in the literature is also studied. From the experiment it was found that in the turbulent flow regime, rotational speed plays an important role during the heat transfer process, while the gap width is of minor significance.