What is a Scraped Surface Heat Exchanger？
Scraper heat exchanger is a heat exchange equipment especially suitable for processing viscous, high viscous, granular liquid or liquid products requiring certain crystallization applications. It is usually used for heating and cooling, crystallization, pasteurization, steaming, disinfection, gel, concentration, freezing, evaporation and other continuous production processes in food processing, petrochemical, pharmaceutical and other industries. In the treatment process of the scraper heat exchanger, the feed liquid is in contact with the heat transfer surface. At the same time, the boundary layer of the feed liquid is continuously replaced by new feed liquid by continuously scraping the heat transfer surface through the scraper. While obtaining a very high heat transfer coefficient, it can avoid adverse phenomena such as coking film on the heat transfer surface. Due to the scraping and stirring of the scraper, the materials can be fully mixed, so the scraper heat exchanger has the advantages of high heat transfer efficiency and uniform heat exchange effect. In addition, in the continuous production process, the materials usually stay in the scraper heat exchanger for only a few seconds, so the higher temperature gradient can be used for instantaneous heat transfer, and other undesirable side effects will rarely occur. Therefore, scraper heat exchanger is favored by candy, ice cream and other manufacturers.
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.
What Products Does Scraped surface heat exchanger Do?
• 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.