Numerical analysis of thermal performance of waste heat recovery shell and tube heat exchangers on counter-flow with different tube configurations

Abstract

This study investigates the effect of tube layout configurations on the hydraulic-thermal performance of shell-and-tube heat exchangers (STHXs) as waste heat recovery systems. The STHXs are triangular (30°, STHX-T), rotated triangular (60°, STHX-RT), and combined (STHX-C). Water at a temperature of 10 °C was circulated through a bundle of tubes inlet to recover waste heat from hot water at the temperature of 65 °C. Water was circulated through the shell inlet within the mass flow rate range of 0.5 ≤ ṁ ≤ 3.5 kg/s. ANSYS-Fluent was used to perform a three-dimensional computational study under steady-state conditions. The turbulence model, realizable k-epsilon, was adopted because of the possible transition from laminar to turbulence. The results were validated with the Kern correlation for shell-side heat transfer coefficient and pressure drop. The temperatures, pressure drop, velocity, and overall heat transfer coefficient for all the cases were compared. Temperature contours, pressure contour, velocity vector, and velocity contour were presented for flow visualization. When the simulation results of the different STHXs were compared, the results revealed that the STHX-T layout has the highest overall heat transfer coefficient of 2307.09 W/m2K. The maximum pressure drop of 242.42 Pa, highest temperature drop in the shell zone of 4.48 K, and highest temperature rise in the tube side of 6.67 K, followed by STHX-C and STHX-RT layout were obtained.

Keywords

• CFD
• Realizable k-epsilon
• Shell-and-tube heat exchanger
• Waste heat recovery system
• Thermal performance
• Pressure drop