| dc.description.abstract | As industry develops, there is an increasing demand on energy. The development of energy-saving devices and renewable energy have been emerging issues around the world. Organic Rankine cycle, ORC, is a technique to generate power from low temperature heat sources. ORC is used in recycling industrial waste heat, solar energy and geothermal power generation. Waste heat below 230°C is called low-grade waste heat. Low-grade waste heat cannot be efficiently reused in process, so it is usually exhausted into the environment. In this research, we perform thermodynamic analysis on low-grade waste heat recycling ORC systems. R134a,R1234yf, R227ea, R245fa, and Propane are used as working fluids and their max system thermal efficiency and net power output is calculated. We discuss the effect of different evaporation pressure and evaporation temperature to the system performance with different conditions of three heat source temperatures, 100°C, 150°C,and 200°C, and four pinch point temperature differences, 5°C,10°C,15°C, and20°C by iteration methods to find the optimum parameters. The result shows that R245fa has the highest net work output of 505.5kW and system thermal efficiency of 15% at heat source temperature of 200°C. In this research, we use brazed plate heat exchangers as example. We use the optimum conditions to calculate the total heat transfer area and evaluate the constructing costs of the heat exchanger. It is found that the higher heat source temperature, the lower cost it needs. When the propane is used as working fluid, the lowest cost can be achieved with heat source temperature at 150°C、200°C. | en_US |