Modeling and analysis of a transcritical rankine power cycle with a low grade heat source

摘要

A transcritical carbon dioxide (CO2) Rankine power cycle has been analyzed based on first and second law of thermodynamics. Detailed simulations using distributed models for the heat exchangers have been performed in order to develop the performance characteristics in terms of e.g., thermal efficiency, exergetic efficiency and specific net power output. A generic cycle configuration has been used for analysis of a geothermal energy heat source. This model has been validated against similar calculations using industrial waste heat as the energy source. Calculations are done with fixed temperature and mass flow of the heat source. The results show the existence of an optimum high pressure for maximizing performance and for minimizing the heat transfer area. The exergy analysis specifies points of potential improvement in the heat exchanger temperature match and points to optimal operating conditions for the high side pressure. In addition the results underline that the investment cost for additional heat exchange components such as an internal heat exchanger may be unprofitable in the case where the heat source is free.