Thermal performance analysis of a novel geothermal Organic Rankine cycle-bypass flash system based on the latent heat proportion of working fluids

Abstract

To reduce the temperature difference of the heat exchanger and improve the thermal performance of organic Rankine cycle (ORC), a novel geothermal ORC-bypass flash system (ORC-f) is proposed. In this system, the latent heat proportion of working fluid and the saturated temperature of heat source are used as the basis for judgments. Further, the influence of heat source temperature and evaporation temperature on the ORC-f system is analyzed with different working fluids and compared with that of ORC system. The results show that when the heat source temperature is 403.15 K, the evaporation temperature is 313 K and 397 K, using R123 with higher latent heat proportion as working fluid, the net output power of ORC-f system is increased by 6.3 kW and 551.23 kW than that of the ORC system; using R114 with lower latent heat proportion as working fluid, the net output power of the ORC-f system is increased by 3.8 kW and 547.4 kW than that of the ORC system. When the saturated heat source temperature is not reached, the working fluid with higher latent heat proportion is used, the net output power and exergy efficiency of the ORC-f system are larger; When the saturated heat source temperature is reached, there is no need to increase the bypass flash system. Further, the thermal performance of the different working fluids of the ORC-f system is similar, and the ORC-f system can reduce the influence of the working fluid on the thermal performance.

Keywords

• Geothermal water
• Saturation temperature of heat source
• Latent heat proportion of working fluids
• Bypass flash system
• Thermal performance