Research On The Solar Powered United Ejector-vapour Compression Refrigeration System

Since environmental problems and the gap between the supply and demand of energy resources become more and more severe, solar energy has been paid more attention to in the world. As a result, the development of solar cooling technology by thermal compression has been one of the research focuses in the refrigeration and air conditioning world. In this thesis, a solar powered united ejector-vapour compression refrigeration system (SPUEVCRS) is proposed. The SPUEVCRS and its main components are studied through theoretical calculation, analysis of energy consumption and experiment. The main work and results include the following five aspects.1. The SPUEVCRS is first proposed in this thesis and the experimental system is designed and set up. It unites the solar collecting system and the booster assisted ejector refrigeration system (BAERS) with the same working fluid and it can work well in use of varied-speed technology no matter there is sunshine or not. Comparison between the SPUEVCRS and the solar ejector refrigeration system (SERS) shows that the former can work at a higher condensing temperature with a pressure lift ratio which is about 44.3% larger than the latter, and it, with a higher coefficient of performance, needs less solar collector areas which is about 35.7% less than that of the SERS under the condition of same cooling capacity, and it has a higher coefficient of primary energy utilization. Comparison between the SPUEVCRS and the vapour compression refrigeration system (VCRS) shows that the former has higher mechanical COP under the same compressor rotate speed and operating conditions, and its mechanical COP is about 112% larger than the latter at a condensing temperature of 42℃. Comparison between the SPUEVCRS and the BAERS is also carried out. The result shows that the SPUEVCRS can meet the demand of the buildings cooling load better when there is enough solar radiation, and it has a higher coefficient of primary energy utilization when here is not enough solar radiation.2. The calculation model of thermal performance of heat-pipe evacuated tubular collector/generator is set up for the first time on the base of two-phase flow and heat transfer theory, and experiment is carried out also. By the regression of experimental dates, the instantaneous efficiency equation of the collector/generator is given. The research result shows that the efficiency of collector/generators in two-phase state is greater than that in one-phase fluid state, and the thermal-collecting temperature andflow rate have great influence on the efficiency.3. On the base of gas dynamic analysis of ejector, a ejector designing model by the constant rate of real gas momentum change (CRRGMC) method is set up. The CRRGMC method makes use of advantages of the constant rate of momentum change (CRMC) method proposed by Eames and the numerical designing method, and the thermodynamic properties of working fluids are calculated by real gas state equations. Comparison is made between the ejector designed by the CRRGMC method (ejector A) and the ejector designed by the constant pressure method (ejector B). The result shows that ejector A is better than ejector B in performance as the CRRGMC method produces a diffuser geometry that removes the thermodynamic shock process within the diffuser at the design-point operating conditions. The pressure lift ratio of ejector A is about 9.1% in calculation and about 4% in experiment greater than that of ejector B.4. Experiment on the performance of SE508 compressor with R141b acted as its working fluid is made firstly at different operating conditions and rotating speeds.5. A new method, solar radiation frequency method, is given to calculate the long term cooling capacity and energy consumption of solar refrigeration systems. By use of the method, a comparison is made between the SPUEVCRS and the SERS with a oil boiler acting as its assisted-power device. And the result shows that the summer energy consumption of the former is about 63.4% less than the latter.