Thermodynamic analysis of refrigerants used in ORC-VCC combined power systems for low temperature heat sources

Abstract

Fossil resources are largely used for energy supply. This situation causes environ?mental pollution. In recent years, studies in the field of more environmentally friend?ly and sustainable energy conversion technologies have increased. In this context, organic Rankine cycle (ORC) technology is combined with RES. In this study, combined ORC and vapor compression cycle (VCC) were investigated. The electricity produced in the combined ORC-VCC system was used both in the compressor of the VCC system and in the plant. The main factor affecting the efficiency of the combined ORC-VCC system is the refrigerant. Therefore, it is necessary to examine the selection of the most suitable refrigerant for an ORC-VCC based system. Fifteen different refrigerants were optimized with the enginering equation solver program, and energy and exergy analyzes of the systems were made separately. According to the results, the best energy efficiency and COP values among the refrigerants was found to be R40 (?ORC = 0.1206) for the ORC system and R113 (COP = 4.405) for the VCC system. For all system components in the VCC, the most exergy destruction occurs in the evaporator, followed by the compressor, condenser, and throttle, respectively. In ORC, the most exergy destruction is in the evaporator, followed by the condenser, tube and pump, respectively. The total efficiency was found to be (? = 0.53) for the combined ORC-VCC system. The total exergetic efficiency was found to be (?glob = 0.26) for the combined ORC-VCC system.