Numerical investigation of turbulent entropy production rate in conical tubes fitted with a twisted-tape insert

Abstract

This paper investigates the turbulent entropy production rate of water flow in convergent and divergent pipes with and without twisted tape inserts for the first time. A carefully validated numerical model was adopted using Ansys-Fluent with k − ε model. The effect of Reynolds number (3 × 103 ≤ Re ≤ 4.5 × 105), diameter ratio (1.0, 1.5, 2.0, 3.0, and 5.0), and the presence of twisted tape inserts on entropy production rate (EPR) were examined. The result shows that the twisted tape insert increases the viscous entropy production rate (VEPR) but reduces the thermal entropy production rate (TEPR). Also, the TEPR is higher in the divergent pipe than in the convergent pipe. However, the opposite is the case for the VEPR. Furthermore, increasing the diameter ratio increases the divergent pipe's TEPR while decreases it in the convergent pipe. The ratio of TEPR in divergent pipe of diameter ratio 3 to a similar one of diameter ratio 1.5 is 1.26. The corresponding value in converging pipes is 0.96. The combination between the conical tube configurations and TT significantly influences the entropy characteristics. Lastly, two new correlations based on response surface methodology were developed to estimate EPR in convergent and divergent pipes with twisted tape inserts. The results show that the Reynolds number, diameter ratio, and interaction between the two are statistically significant to EPR.