Concentric tube heat exchanger

Concentric tube Heat Exchangers are used in a variety of industries for purposes such as material processing, food preparation, and air-conditioning. They create a temperature driving force by passing fluid streams of different temperatures parallel to each other, separated by a physical boundary in the form of a pipe. This induces forced convection, transferring heat to/from the product. Concentric tube Heat Exchangers are used in a variety of industries for purposes such as material processing, food preparation, and air-conditioning. They create a temperature driving force by passing fluid streams of different temperatures parallel to each other, separated by a physical boundary in the form of a pipe. This induces forced convection, transferring heat to/from the product. The thermodynamic behaviour of concentric tube heat exchangers can be described by both empirical and numerical analysis. The simplest of these involve the use of correlations to model heat transfer; however the accuracy of these predictions varies depending on the design. For turbulent, non-viscous fluids the Dittus-Boelter Equation can be used to determine the heat transfer coefficient for both the inner and outer streams; given their diameters and velocities (or flow rates). For conditions where thermal properties vary significantly, such as for large temperature differences, the Seider-Tate Correlation is used. This model takes into consideration the differences between bulk and wall viscosities. Both correlations utilize the Nusselt number and are only valid when the Reynolds number is greater than 10,000. While Dittus-Boelter requires the Prandtl number to be between 0.7 and 160, Seider-Tate applies to values between 0.7 and 16,700.