Thermodynamic investigation of low-temperature industrial waste-heat recovery in combined heat and power generation systems

Performance analysis of an industrial waste heat-based combined heat and power systems (WHCHP) completely uses energy and exergy efficiency parameters. The effect of waste water mass flow rate, pressure and temperature, organic fluid types on both energy and exergy efficiencies and economical profit of the system is investigated by a computer simulation. The first step of the analysis is the selection of the suitable working fluid. After that, in order to get the performance indicators, different scenarios are run by computer simulation for WHCHP. The most suitable working fluid is found out as isopentane. The work output and economical profit increase while exergy destruction decreases with increasing turbine inlet pressure. On the other hand, with the increase in the energy of the process heater, the work output decreases but exergy destruction and utilization factor increase. Finally, these results clearly show that performance evaluation of WHCHP based on energy analysis is not adequate and hence more meaningful evaluation should include exergy analysis.