Theoretical thermal analysis of heat recovery by two phase closed Thermosyphon from engine exhaust

Due to the increase in energy requirements for various process industries and depletion of fossil fuel reservoirs, it is necessary to recover the heat energy which is exhausted to the environment from different sources. Effective utilization and recovery of waste heat is of great importance for the preservation of energy sources and protection of an environment and health hazards. For many industrial practices because of high effectiveness the application of Thermosyphon is increasing for the recovery of waste heat. The focus of the present study is to investigate theoretically the performance parameters (thermal and geometrical) of the Single tube wickless heat pipe heat exchanger (Thermosyphon) for heat recovery at simulated diesel engine exhaust conditions (Air temperature of ~150, 250 and 350 °C and under forced convective heating and cooling at different Reynolds number). From the theoretical analysis it was observed that effectiveness of Thermosyphon was over 50% for each of the conditions and it was increased up to 88% with decreasing inlet hot air velocity down to 1 m/s at temperature of 350 °C. It was also observed that at equal heat capacity rate of hot and cold fluids the effectiveness is minimum.