Energetic and Exergitic analysis and Optimization of Organic Rankine cycle (ORC) for Waste heat recovery

Increase of fuel price and limitation of carbon dioxide emission caused development of different techniques to enhance the thermal efficiency of internal combustion engines. One of these techniques is conversion of the waste thermal energy in the engine to mechanical or electrical energies. This investigation concentrated on simulation, examination and application of waste heat from exhaust gases of MTU-16V internal combustion engine in an organic Rankine cycle based on the efficiency of first and the second laws of thermodynamics. Using 862 kW power of exhaust gases waste heat, the net powers of working fluids including R600a, R600 and R245fa were evaluated and the highest net output power was calculated to be 37.23 kW for R245fa working fluid. This working fluid increased the output power to approximately 2% and 6% in comparison with R600 and R600a fluids, respectively. Moreover, the mentioned working fluids were examined for volumetric flow rate and required volume contraction, where the lowest value was obtained for R600a. On the one hand, the effect of turbine inlet temperature on the volumetric flow rate, and effect of turbine inlet pressure on energy efficiency, exergy efficiency and irreversibility of the whole system were investigated. On the other hand, the influence of ambient temperature increase on irreversibility of each system component was studied. Based on the obtained results, R245fa fluid showed the best performance to be used in organic cycle from the viewpoint of the first and second laws of thermodynamics.