Methods and measures to reduce or eliminate scale formation

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(1) From a design perspective, reduce or eliminate the conditions that lead to scaling. The design of a heat exchanger involves determining, through calculations, an economically reasonable heat transfer area as well as the relevant structural dimensions of the heat exchanger, in order to achieve the desired heat transfer performance. When designing the structure, it may be advisable to consider using special designs, such as those that generate turbulence. For important heat exchange equipment, electronic descalers and backwashing systems can also be employed. If water is used as the heat exchange medium, anti-scaling additives and other materials should be used to address corrosion issues. In addition, adhering to simple design principles can also reduce or even eliminate the external conditions that lead to scaling; for example, unclean and scale-prone fluids should be used in the tube side, as cleaning the tube side is more convenient. (2) Fluids with low flow rates or high viscosity are suitable for flow in the shell side, as the flow of such fluids within the shell side, surrounded by baffle plates, results in continuous changes in flow velocity and direction, thereby achieving turbulence that prevents scale formation. (3) Corrosive fluids should be passed through the tube side to prevent both the tubes and the shell from being corroded, and the tube side also facilitates maintenance and replacement. (4) The cooled fluid should flow in the shell side, allowing use of the shell’s external heat dissipation capability; moreover, it is easier to replace the tubes when scaling occurs on them. (5) Saturated steam should flow in the shell side, as it is relatively clean and not prone to scaling, thus eliminating the need for cleaning. Selection of fluid flow rate: The selection of fluid flow rate involves aspects such as the heat transfer coefficient, flow resistance, and the structure of the heat exchanger. Increasing the flow rate can raise the convective heat transfer coefficient, reduce the formation of fouling, and thereby increase the overall heat transfer coefficient ； But at the same time, it increases flow resistance and raises power consumption ； Choosing a high flow rate reduces the number of tubes; for a given heat exchange area, longer tubes or more passes are required. Too long tubes make cleaning difficult, and changing from a single pass to multiple passes reduces the average heat transfer temperature difference. Therefore, it is generally necessary to consider multiple factors in order to select an appropriate flow rate. A fixed-tube-sheet heat exchanger is selected when the temperature difference is small, scaling of the shell-side fluid is not severe, and chemical cleaning can be used for the shell side.