Thermal performance analysis of organic flash cycle using R600A/R601A mixtures with internal heat exchanger

Abstract

In this study, the thermal performance of an internal heat exchanger-organic flash cycle system driven by geothermal water was investigated. The R600a/R601a mixtures were selected as the working fluid. The effects of the mole fraction of mixtures on the heat absorption capacity of the heater, the temperature rise of cold working fluid in the internal heat exchanger, net power output, thermal efficiency, and electricity generation costs were analyzed. The net power outputs, electricity generation costs, and thermal efficiency of the internal heat exchanger-organic flash cycle and simple organic flash cycle systems were com-pared. Results showed that the system using the R600a/R601a mixtures (0.7/0.3 mole fraction) has the largest net power output, which increased the net power output by 3.68% and 42.23% over the R601a and R600a systems, respectively. When the R600a mole fraction was 0.4, the electricity generation costs reduction of the internal heat exchanger-organic flash cycle system was the largest (1.77% compared with the simple organic flash cycle system). The internal heat exchanger can increase the thermal efficiency of organic flash cycle, but the net power output does not necessarily increase.