Heat exchangers often play a key role in wastewater treatment, and all but the most basic heat exchangers are created to a bespoke brief, designed to take into account the material/s being heated or cooled, the heating or cooling medium, the amount of effluent being processed, velocity, risk of fouling and a host of other factors. Over the last 150 years or so, a wide variety of types and designs of have emerged, meaning that finding the most suitable heat exchanger for your application is not always simple.
The first consideration to bear in mind is the nature of the material being processed, in particular its viscosity and whether it contains particles. The simpler and less viscous the material, the simpler the heat exchanger can be. As materials become thicker, or contain suspended particles or large solids, then heat exchange becomes more difficult, and more sophisticated designs are required to guarantee the necessary performance. Starting with simple multi tube designs, the range moves through double tubes – where viscosity is higher or solids are present – and annular space designs for highly viscous products, with the most challenging materials (such as very thick digestate sludges) requiring the use of scraped surface heat exchangers.
Another consideration is what happens in the event of a leak. In certain circumstances a leak can be business critical or cause significant environmental damage. In such cases, double tubeplate multitube heat exchangers should be specified, as these provide leak detection in order to avoid cross contamination between the service and product fluids.