Abstract:The performance characteristics of an ejector-expansion refrigeration cycle (EEC) using R32 have been investigated in comparison with that using R134a. The coefficient of performance (COP), the exergy destruction, the exergy efficiency and the suction nozzle pressure drop (SNPD) are discussed. The results show that the application of an ejector instead of a throttle valve in R32 cycle decreases the cycle's total exergy destruction by 8.84%-15.84% in comparison with the basic cycle (BC). The R32 EEC provides 5.22%-13.77% COP improvement and 5.13%-13.83% exergy efficiency improvement respectively over the BC for the given ranges of evaporating and condensing temperatures. There exists an optimum suction nozzle pressure drop (SNPD) which gives a maximum system COP and volumetric cooling capacity (VCC) under a specified condition. The value of the optimum SNPD mainly depends on the efficiencies of the ejector components, but is virtually independent of evaporating temperature and condensing temperature. In addition, the improvement of the component efficiency, especially the efficiencies of diffusion nozzle and the motive nozzle, can enhance the EEC performance.
The paper takes Tianjin subway as an example, and use the Subway Environment Simulation (SES) program to establish subway system with platform screen doors or different characteristics of two systems to carry out the simulate computation in summer, transition season and winter of the two systems; by analyzing the difference between two environment control modes, get the chart of the temperature distribution characteristic. The table result showed that it has more advantages using closed system than PSD system in Tianjin by using the primary invests and saving energy consumption.
The expo 2010 in Shanghai from May 1st to October 30th has ended, after six months, 55billion dollars, and 73million visitors. According to the rules of the Bureau International des Expositions, the global governing body of Expos, all the pavilions on the expo site should be taken down. However that will put the Shang Hai Expo into dilemma, as which was characterized by its greenness, expo pavilions destruction will create tons of waste instead of “better city, better life”. Except for the China Pavilion and Expo performance centre, other pavilions have to wait to be chosen either remained or removed to other location. Therefore this thesis is trying to make some case analyses of the Expo pavilion in the history and explore the potential of the temporary building.
In recent years, Afghanistan has experienced sustained political instability that is rooted in a relatively low level of modern nation-state building. The traditional tribal and Islamic conservationists are too powerful and restrict the process of nation-state building in Afghanistan. The logic behind a traditional tribal society and a modern nation-state is different, and their power has inherent contradictions in terms of attributes, vectors, and fields of action. The religious conservative tendency fetters the modernization of Afghanistan in different aspects, and the absolute religious right negates national power in concept. In reality, the localization of teaching law eliminates national ability, and fundamentalism stifles the vitality of society. The tribal and religious policies of the new Taliban government will shape the future of Afghanistan politics.
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