Twisted Tape in Double-pipe Heat Exchanger CFD Simulation, ANSYS Fluent Training

To increase heat transfer efficiency in double-pipe heat exchangers, twisted tape inserts are a commonly utilized enhancement technique. The fluid flow is forced into a spiral motion by inserting a twisted tape inside the inner pipe, upending the laminar boundary layer and increasing turbulence. As a result of the increased turbulence, the fluid mixes better and the heat transfer coefficient rises greatly, improving thermal performance. This CFD simulation is contingent upon the reference paper entitled “ Numerical study on heat transfer enhancement and flow characteristics of double pipe heat exchanger fitted with rectangular cut twisted tape”.

Simulation Process

One of the most challenging parts of the present simulation is designing the twisted tape inside the inner tube of the double-pipe heat exchanger. It is modeled using Design Modeler software. Then, a hexagonal grid is produced. The article represents an estimation of water properties by Regression equations in Table 4. Consequently, a User-defined Function is written to employ all the properties dependent on temperature.

Post-processing

A significant improvement in the heat transfer performance was shown in the simulation of the double-pipe heat exchanger with twisted tape inserts. After the twisted tape was installed, there was a noticeable rise in the Nusselt number, a dimensionless measure of convective heat transmission in comparison to conductive heat transfer. Nusselt number before installation was 34.52. Once the twisted tape was added, the Nusselt number increased to 43.16. This significant increase shows how well the twisted tape works to break up the thermal boundary layer and generate turbulence, both of which improve convective heat transfer.