Scraped Surface Heat Exchangers

Scraped surface heat exchangers (SSHEs) are commonly used in the food, chemical, and pharmaceutical industries for heat transfer, crystallization, and other continuous processes. They are ideally suited for products that are viscous, sticky, that contain particulate matter, or that need some degree of crystallization. Since these characteristics describe a vast majority of processed foods, SSHEs are especially suited for pumpable food products. During operation, the product is brought in contact with a heat transfer surface that is rapidly and continuously scraped, thereby exposing the surface to the passage of untreated product. In addition to maintaining high and uniform heat exchange, the scraper blades also provide simultaneous mixing and agitation. Heat exchange for sticky and viscous foods such as heavy salad dressings, margarine, chocolate, peanut butter, fondant, ice cream, and shortenings is possible only by using SSHEs. High heat transfer coefficients are achieved because the boundary layer is continuously replaced by fresh material. Moreover, the product is in contact with the heating surface for only a few seconds and high temperature gradients can be used without the danger of causing undesirable reactions. SSHEs are versatile in the use of heat transfer medium and the various unit operations that can be carried out simultaneously. This article critically reviews the current understanding of the operations and applications of SSHEs.

Keywords:

• SSHE
• crystallizer
• food processing
• heating
• cooling
• ice cream
• particulate flow

Notes

^a Approximate values, product dependent.

^b Perfector series come in several models based on capacities (92, 92R, 105B, 125, 180, 250). Here the data for 250 is presented. 1–6 chilling tubes can be used for each model. Data is given per chilling tube.

^c Comes in various models.

^d Kombinator series come in two model based on product viscosity requirements (KN and LN). Here the data for KN, which is designed for viscous products with toughest requirements.

^e Gaps can be custom designed within the range.

^f Comes in different models based on capacity. Data presented for model “T2”.