Analysis And Experimental Study On The Performance Of Organic Rankine Cycle Systems In Low Temperature

Energy is the material basis for human survival and development. The rapid growth of the world economy, had greatly accelerated the consumption of non-renewable energy. In recent years, with the rapid development of China’s economy, it has increased energy consumption. Energy shortage is becoming increasingly prominent, and the extensive use of fossil fuels has also brought serious environmental pollution and ecological destruction. Greenhouse gas emissions from burning fossil fuels, is an important factor in global greenhouse effect. Cutting down greenhouse gas emissions, mitigation of global warming process, have reached an extensive consensus on the worldwide. Now we are facing the shortage of primary energy. For the low-temperature energy is Inexhaustible, on the background of using low-temperature energy, we conducted a study of low-temperature power generation combined with ORC.Based on the researches of related fields with home and abroad, we conducted an experiment to analysis the dynamic characteristics of ORC. We selected R245 fa as the fluids and built the thermodynamic model to make the theoretical analysis. This paper analysis the physical parameters of R245 fa under different working conditions and on the basis of the established mathematical model worked out the basic operating point of ORC thermal power system 5-kW power scale through the trial method. And then uses the software to simulate the 5-kW power generation scale. The purpose of this paper is to analysis of evaporating temperature, condensing pressure, hot source temperature effect on the performance of the ORC system. The result shows that under a certain given heat source, a significant way for improving overall power output and thermal efficiency of the ORC system is to increase the difference between evaporating temperature and condensing temperature.There are important effects if the heater exchanger can match the equipments of the whole ORC system. Analysis the ORC system using pinch point temperature difference technology. The results show that, the best pinch point temperature difference decreases when the hot source temperature increases, while the best evaporation temperature increases. When the hot source temperature is 363.15 K,the best pinch point temperature difference is 4K and the evaporation temperature is 332.15K;while when the hot source temperature is 373.15 K,the best pinch point temperature difference is 3K and the evaporation temperature is 340.15 K.Based on theoretical calculation results, in this paper a serious of performance tests aimed at ORC system have been carried out with R245 fa, HFE-7100 as working fluids. This paper conducted tests with the working fliud of R245 fa, and the experimental result shows that with a constant heat source temperature, a relatively stable value of evaporating pressure, evaporating temperature of working medium, liquid level and rotating speed of working fluid pump, the system has the ability to run in a relatively stable condition. Under the relatively steady condition of heat source temperature of 332 K, evaporating pressure of 4.5bar and liquid level of 300 mm, the rotating speed of working fluid pump also shows a relative steady value of 1200r/min. According to the results of the R245 fa performance tests, the maximum of system output power is as high as 894.6W, and the maximum system thermal efficiency reaches 4.1%. Through the HFE-7100 performance tests, we get the conclusion that with both different working fluids the dynamic performance variation trends are similar. Meanwhile, it shows quite an obvious system output power difference when the heat source temperature is lower than 373.15 K. Under above condition, the system with HFE-7100 as working fluid has a lower maximum system output power of 45 W compared with 894.6W from the one with R245 fa as working fluid.