Concentric Tube Heat Exchanger - Concentric Tube Heat Exchanger Design

Concentric Tube Heat Exchanger Design

The primary advantage of a concentric configuration, as opposed to a plate or shell and tube heat exchanger, is the simplicity of their design. As such, the insides of both surfaces are easy to clean and maintain, making it ideal for fluids that cause fouling. Additionally, their robust build means that they can withstand high pressure operations. They also produce turbulent conditions at low flow rates, increasing the heat transfer coefficient, and hence the rate of heat transfer. There are significant disadvantages however, the two most noticeable being their high cost in proportion to heat transfer area; and the impractical lengths required for high heat duties. They also suffer from comparatively high heat losses via their large, outer shells.

The simplest form is composed of straight sections of tubing encased within the outer shell, however alternatives such as corrugated or curved tubing conserve space while maximising heat transfer area per unit volume. They can be arranged in series or in parallel depending on the heating requirements. Typically constructed from stainless steel, spacers are inserted to retain concentricity, while the tubes are sealed with O-rings, packing, or welded depending on the operating pressures.

While both co and counter configurations are possible, the countercurrent method is more common. The preference is to pass the hot fluid through the inner tube to reduce heat losses, while the annulus is reserved for the high viscosity stream to limit the pressure drop. Beyond double stream heat exchangers, designs involving triple (or more) streams are common; alternating between hot and cool streams, thus heating/cooling the product from both sides.