CFD analysis of heat transfer augmentation for flow through a tube using wire coil inserts

Abstract

The need to increase the thermal performance of heat transfer equipments has led to the development and use of many heat transfer augmentation techniques. This project deals with the analysis of heat transfer augmentation for fluid flowing through pipes using CFD. Friction factor and Nusselt number for water flowing through the specified pipe (internal diameter = 0.022 m, length = 2.5 m) were obtained first for the smooth pipe and then for the pipe with a wire coil insert in the Reynolds number range of 250 to 25,000 and Prandtl number of 6.97. Three wire coils with pitch 0.033 m, 0.044 m and 0.0484 m, and coil diameter 0.00154 m, 0.00187 m and 0.002 m respectively were considered. Calculated values (obtained from empirical equations available in literature) were compared with CFD values. Comparisons were also made between the smooth tube results and the coiled wire results to establish the heat transfer augmentation due to the use of insert. It was seen that the friction factor increment i.e. fc/f0 varied between 1.2 to 8.5 with coil 1 giving the maximum value of 8.5 at Reynolds number 2250. Similarly, the Nusselt number increment i.e. Nuc/Nu0 varied in the range of 1.3 to 4.9, again with coil 1 giving the maximum value of 4.9 at the same Reynolds number of 2250. Simulations were carried out using commercial CFD software ANSYS 13.0.