Before deciding on the design and dimensions of a heat exchanger to handle viscous products such as ketchup or yoghurt, you need to know the key characteristics of the product. Here are the questions you need to ask:
Just measuring the viscosity of a liquid using a standard Brookfield viscometer is not enough. Shear rates affect viscous food products, which are usually either shear thinning or shear thickening.
For example, products containing starch must have two tests run. One when the product is heated and the starch blooms, and then a second test as the product cools and thickens. You can give a sample of your product to the heat exchanger designer so they can perform the necessary tests over a range of temperatures and shear rates.
Viscosity plays an important part in the overall heat transfer coefficient, and thus determines the amount of heat transfer surface the heat exchanger must have to perform the thermal duty. Not knowing the actual viscosity can result in an oversized or undersized heat exchanger.
You have to ask the right questions. Based on the answers to the questions above, a heat exchanger can be designed and dimensioned to deliver the necessary amount of heat transfer efficiently.
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