Simulation of Thermosyphon Rankine Engine

Abstract

The increasing global energy demand has led to other alternative ways of harvesting energy from renewable resources. This energy cause less environmental pollution and deterioration of humans' health. Thermosyphon Rankine engine (TSR) is a concept used for direct electrical power generation from low-grade heat sources. In this project, an extended investigation on previous experimental done was conducted through a simulation approach using Computational Fluid Dynamic (CFD) analysis to simulate a two-phase flow, phase change occurred during evaporation and condensation processes inside the thermosyphon under different power inputs of 245 W, 552 W, and 984 W. Also the water was used as a working fluid. The volume of fluid (VOF) technique was used to model the phase change using ANSYS FLUENT software. The simulation investigated temperature profile, water volume fraction, and velocity. Then, CFD predicted temperature profile was compared with the previous experimental data, and percentage error was calculated. Compared to the experimental one, CFD predicted temperature profile was higher than the experimental one due to mechanical losses during experimentation. Meanwhile, the model managed to simulate vapor bubbles and nucleate boiling during phase change. It showed that the VOF model with the in-built evaporation-condensation model developed by Lee only simulated nucleate boiling at the interphase between water and vapor phase during evaporation and condensation processes.