Flow Characteristic and Pressure Drop Inside the Horizontal Scraped Surface Heat Exchanger

Abstract

Thermal processing (heating, cooling, crystallization) of high viscous or sticky products, usually containing particles or alter state when thermally processed are managed in chemical, food and consumption industry by scraped surface heat exchangers. These products are in most of the time non-Newtonian and sensitive products. Because of intensive presence of fouling and low heat transfer coefficient the rotating shaft (usually speaking of votator type of scraped surface heat exchangers) is equipped with scraper blades to keep clean the heat transfer surface and to mix the product as much as possible from the heat transfer surface into the main axial flow. Often, at the entrance of the product from the inlet cell to the main cylindrical heat exchanger part, a specific static mixers, homogenizers are applied (at outlet as well, but for different purpose -make additional mixing after thermal processing of the product). At inlet side the mixers are applied to flatten the velocity profile which is beneficial for the heat exchange process. The presented paper deal with the type of static mixers at the entrance and outlet from the point of view how the velocity profiles looks like and what is the effect on the pressure drop through them. The results show that the usage of different type of the mixers have no significant effect on the velocity profile when product is already managed by rotating scrapers. On the other hand it has quite significant impact on the pressure drop, what can lead to the higher energy consumption.