Performance Evaluation of Two Medium-Grade Power Generation Systems with CO2 Based Transcritical Rankine Cycle (CTRC)

Abstract

As CO2 is emerging as an environment friendly working fluid its application in high temperature engine’s waste heat recovery systems is found to be more suitable than other hydrocarbons. This paper presents a performance comparison of two systems based on transcritical Rankine cycle using CO2 as working fluid. A heavy-duty truck is opted for analysis in which coolant is used to preheat CO2 and further the engine exhaust is used to transfer the heat to main heater. The System-1 and System-2 having single and dual loop based transcritical Rankine cycle are analysed. The independent parameters taken for the investigative analysis are turbine inlet temperature (TIT), pressure ratio and effectiveness of heat exchangers. Comparison results show that System-2 is producing 11.8 kW more power than system-1 at 12 MPa pressure ratio and at 489°C TIT. However, under same conditions, system-1 is having 16.88% of thermal efficiency which is higher than system-2 by around 3%. Further, the Engine coolant utilization rates when compared are nearly same in both the systems, the exhaust gas utilization rate came out higher for System-2. In respect of exergy destruction, system-1 shows maximum destruction in regenerator and System-2 in heater-2.