Investigation On A Two-stage Ejection-refrigeration System Under High Condensing Temperatures

The increasing consumption of energy has become a serious problem nowadays.In order to reduce fuel consumption and greenhouse gas emission, ejection refrigeration system is chosen as a way to solve the problem. Ejection refrigeration system is able to utilize low grade heat such solar power or waste heat. With a little aid by electricity, this system can be driven by low grade heat, which suits the goal of energy saving. In order to make ejection refrigeration systems more efficient in real application circumstances, a two-stage ejection refrigeration system is presented in this study. The objectives and conclusions are presented as follows:1) This research gives a detailed review on developments on both ejection refrigeration systems and the performance of ejectors. Based on the knowledge and experience on ejection refrigeration systems, experimental setups are upgraded, measuring instruments are installed specifically to make the results precise.2) The experimental setup is designed at a best performance under boiling temperature of150℃, condensing temperature of54℃and evaporation temperature of13℃. The COPs of the system are tested under design and off-design working circumstances, and the result of single-stage ejection system is compared with two-stage ejection system. The result shows that two-stage ejection refrigeration system has better performance especially under high condensing temperature and low evaporating temperature.3) Experimental results under different condensing temperatures shows that the main advantage of two-stage ejection refrigeration system is that it can operate with higher COPs under high condensing temperatures. However, the extra power input to drive the second stage ejector makes the system less efficient when working under low condensing temperatures.4) Both thermal calculation of the ejectors and experimental results shows the performance change of both the single and two-stage ejectors under different working conditions, and reveals the relationship between ejectors and the whole system’s performances.