CFD simulation of helical coil heat exchanger with Different coil pitch to heating heavy fuel oil

Abstract

In current work, CFD simulation of "shell and helical coil heat exchanger" has been done using ANSYS FLUENT package 19.2. Numerical study involved design of helical tube with different curvature ratio (di/Dc) 0.166, 0.153, and 0.142 and different coil pitch (30, 50, 75, and 100) mm has been chosen to study the effect of curvature ratio and coil pitch. In shell side cold fluid (oil) "flow rate" is varying from (0.06 - 0.1) kg/s and hot fluid (air) velocity ranges are from (20 to 48) m/s in helical tube with inlet temperature (200, 225, 250) °C. It has been found out that increasing "oil mass flow rate" from (0.06-0.1) kg/s cause decreasing "oil outlet temperature" about 3% and increasing "heat transfer rate", with percentage 37%. From numerical results the curvature ratio 0.142 gives higher heat transfer rate and oil outlet temperature while higher Dean number and Nusselt number in coil with curvature ratio 0.166. Also, results show increases of coil pitch led to increasing in overall heat transfer coefficient and Nusselt number of the shell side. while, heat transfer, oil outlet temperature effectiveness and pressure drop, decreases along the coil with increasing coil pitch.