Analysis of Organic Rankine Cycles Using HFC and HC-based Zeotropic Mixtures under Different Heat Source Temperatures

orc2019 Tracking Number 53

Owing to growing industrialization, the energy consumption has increased considerably over the past few decades, which has led as acid rain, ozone layer depletion, and global warming. Most industries exhaust a lot of low-grade heat to environment, especially as temperature below 100 ℃. For low-grade heat, ORC (organic Rankine cycle) is one of effective methods for conversion of low-grade heat into electricity. Conversion efficiency of ORC is significantly affected by the temperature difference between heating and cooling source, and working fluids. Actually, working fluids cause great damage on the environment, especially for high global warming potential (GWP). Hydro-fluorocarbon (HFC) refrigerants, which have high GWP, but they are popular working fluids owing to excellent conversion efficiency in low-grade heat. By contrast, hydro-carbon (HC) refrigerants have low GWP and high flammability, and they’re suitable in high and medium temperature of the heat source. To achieve high conversion efficiency of system and low GWP of working fluids, HFCs and HCs could be mixed to use as working fluid in ORC system. The purpose of the present study was to develop a thermodynamic analysis model by using MATLAB and to investigate performance of the mixtures at heat source temperature ranging from 100 to 210 ℃. Meanwhile, the evaporate temperatures was set at 70℃. In the present study, R290, R134a and R1234yf with low critical temperature were mixed with R245fa and R600a with high critical temperature to investigate effect of the inlet temperature of the heat source on the optimal mole fraction, change of the evaporate pinch point, first law efficiency of thermodynamic and specific power.