The benefits of shell and tube over plate heat exchangers

13 December, 2022

One element of plate heat exchanges which is often not considered is the cost of gasket replacement.

For simple non-viscous fluids, the choice of heat exchanger normally comes down to a choice between plate heat exchangers (PHEs) and shell and tube designs. The proponents and manufacturers of both types of heat exchanger make strong cases for the use of each technology, and the suitability of each type of heat exchanger, but ultimately the heat transfer situation will determine the best heat exchanger for the role.

Having said that, there are a number of considerations which are not always taken into account when evaluating the advantages of shell and tube and plate heat exchangers. It is first important to understand the difference between the two designs, as this will then make it easier to understand the differences in costs, operational efficiency and maintenance.

As the name suggests, a plate heat exchanger consists of series of pressed metal plates separated by gaskets. The service fluid (which provides the heating or cooling effect) and the product (the material to be heated or cooled) flow through the gaps between alternate plates. In contrast a shell and tube design feature a tube (or series of tubes) running through a shell. The product flows through the tube and the service fluid through the gap between the tube and the shell.

Capital cost consideration

Advantages of plate heat exchangers include their simplicity and high heat exchange performance (when used with simple fluids). However, the capital costs of the two technologies are not always clear cut. Neither are the differences in pressure drop created by the two designs, but tubular heat exchangers are generally capable of operating at higher temperatures.

While PHEs often require less space than tubular units, the exact size difference depends on the design of the tubular unit being compared. Heat exchangers which use corrugated tube technology (such as HRS tubular heat exchangers) to increase thermal efficiency can provide equivalent heat exchanger performance in a smaller package than traditional smooth-tube designs.

Another claimed benefit for PHEs is that they are easy to dismantle and clean but removing lots of separate plates and their corresponding gaskets is not particularly convenient. It also ignores the fact that well designed tubular heat exchangers are less likely to need regular dismantling to allow for deep cleaning, and that this can be facilitated by the use of removable tubes.

A number of manufacturers of PHEs will claim that their designs will operate for years without the need maintenance but will also admit that cleaning (which often involves similar levels of disassembly to servicing) depends on the viscosity, fouling and scaling potential of the product. In other words, admitting that real world performance is much less impressive than the theory. In contrast, corrugated shell and tube heat exchangers are specifically designed to reduce fouling, meaning that their performance parameters are based on real-world operational situations.