What is a Scraped Surface Heat Exchanger and What Does It Do?
Scraped surface heat exchanger were designed to improve upon issues that their predecessors were having problems with. Scraped surface heat exchangers incorporate an internal mechanism which periodically removes the product from the heat transfer wall. Most technologies in direct heat transfer use tubes or flat surface. The goal is to exchange the maximum of heat per unit area by generating as much turbulence as possible. This is achieved by consistently corrupting the tubes, or plates, or extending their surface with fins.
However, in these geometry conformation technologies the calculation of optimum mass flows and other turbulence related factors become diminished at the appearance of fouling. With the appearance of fouling designers are obliged to fit significantly longer heat transfer areas. The different types of fouling, include particulate accumulation, precipitation, sedimentation, generation of ice layer etc.
Another factor posing difficulties to heat transfer is viscosity. Highly viscous fluids tend to generate deep laminar flow, a condition with very poor heat transfer rates and high pressure losses involving a considerable pumping power, often exceeding the exchange design limits. This problem becomes measured frequently when processing non-Newtonian fluids.
Scraped surface heat exchangers have been designed to face the above mentioned problems. It incorporates an internal mechanism which periodically removes the product from the heat transfer wall. The product side is scraped by blades attached to rotating shaft. The blades are made of a rigid plastic material to prevent damage to the scraped surface. This material is FDA approved in the case of food applications.
Typical Applications for Scraped Surface Heat Exchangers in the Food Processing Industry:
• Particulate-Laden Products – Products with particulates which tend to plug conventional heat exchangers are handled easily in scraped surface heat exchangers, and the particulates maintains maximum product identify.
• Food and Meat Processing –Scraped Surface Heat Exchangers can serve the food and meat industries in an extensive variety of applications including; cooling, heating, sterilizing, crystallizing, freeze concentration, or processing a difficult-to-handle products
• Aseptic Processing – Scraped surface heat exchangers have many applications in aseptic processing, particularly those involving viscous and particulate-laden products.