Shell and tube Exchangers and uses

Shell and tube Exchangers and  uses

With a long record of performance in heat-transfer applications, shell-and-tube heat exchangers are the standard by which other models are judged. Tolerant of high pressures and high temperatures, and able to handle high levels of particulate material, they are mechanically simply and relatively unchanged for more than 60 years.

So why consider a change to, for example, plate or spiral heat exchangers? No doubt, some engineers will not. Some have heard horror stories about experiences with different types of heat exchangers, stemming from a lack of training of maintenance personnel or the improper selection of equipment for a particular service. What's more, there is not yet a manufacturers' association, such as the Tubular Exchanger Manufacturers Assn., to propose and promote standards. As a result, construction, quality and capabilities for different brands of the same configuration may vary greatly.

But at a time when processors are under increasing pressure to streamline operations, lower production costs and improve efficiency, engineers may want to consider some of the alternatives to tubular configurations for heat exchangers. Efficient heat transfer can be achieved with equipment that has a smaller footprint, is lighter in weight, and is less expensive to install and operate than traditional designs.

All of the technologies discussed in this article are based on variations of plate, rather than tubular, geometry. All, except the spiral plate, utilize multiple flow channels. For all, hydraulics within the units are vastly different than conventional tubular exchangers and result in increased film coefficients, reducing surface area requirements. This and the tighter packing arrangement possible when using plates, combine to greatly reduce the size and cost of plate heat exchangers, compared with tubular configurations.

Installation costs are significantly lower too, as support requirements are reduced. Piping costs are lower, especially when multiple shells are being replaced with a single compact exchanger. In the case of spiral plate exchangers used as overhead condensers, the units are often mounted directly atop the column. Reflux is performed by gravity, eliminating the need for a reflux drum and pump, as well as the overhead line.