The job of any type of heat exchanger is relatively simple and is used in many different industries. The heat exchanger is made of a material that has superior heat conductivity, allowing heat to flow from one side to the other to cool or heat the two different liquids or semi-liquids on either side.
With a traditional type of heat exchanger, the liquid of one temperature flows through one set of tubes or pipes within a system. On the exterior surface of that pipe is the other liquid, either hot or cold, which is also circulating. As the heat from the hot liquid goes through the exchanger, it cools the warm liquid, bringing both to an equilibrium temperature if the circulation continues for long enough.
The problem with this process is that viscous liquids and semi-solids or solids in suspension don’t act the same as Newtonian liquids like water and they build up along the edges of the tube as the temperature drops and their motion slows. This reduces the ability to heat or cool the material evenly.
The Answer
The answer to this problem is to use scraped surface heat exchangers. As the name implies, these systems use blades or other types of scraping systems to move the material from the exterior walls of the pipe or tube to the middle of the flow of the liquid, resulting in uniform heating and cooling.
The addition of scraped surface heat exchangers also helps to keep viscous materials moving away from the cool wall, allowing for increased flow of material through the system. However, with the design of the blades, this process can even be used for delicate types of products that cannot tolerate rapid agitation.
In scraped surface heat exchangers used in food and beverage production, the blades or the fins are typically made of plastic that is FDA approved for use. This protects both the interior of the tubing carrying the product as well as limits damage to the liquid and solid elements in the flow.
