Exploring performance map: theoretical analysis of subcritical and transcritical power cycles with wet and isentropic working fluids

Abstract

This study examines the overall thermodynamic efficiency of several power cycles, including transcritical power cycle (TPC), trilateral flash cycle, organic Rankine cycle (ORC), partially evaporated ORC, and superheated ORC under both ideal and specific conditions. The research focuses on specific wet and isentropic working fluids, providing a performance map of the power system with identical configurations, internal machine efficiency, and vapor quality. Moreover, this study aims to determine the ideal working fluid to utilize given heat sources by TPC. The results indicate that the efficiency of TPC may reach a maximum and subsequently decrease under certain conditions. Moreover, some operating conditions for the thermal power system, such as temperature range and configurations, may not be recommended due to exceptionally low or negative effective thermodynamic cycle efficiencies. Furthermore, the study demonstrates that increasing the inlet temperature of the working fluid to an expander does not necessarily lead to higher power cycle efficiency, as observed in the case of TPC. However, the result also proves the potential of carbon dioxide (R744) as a promising working fluid when chosen for a TPC with x2,is = 1.00, still achieving positive effective efficiency under specific conditions.