In order to identify the locations of irreversible loss within the transcritical carbon dioxide refrigeration cycle with an expansion turbine, a method with respect to the second law of thermodynamics based on exergy ...In order to identify the locations of irreversible loss within the transcritical carbon dioxide refrigeration cycle with an expansion turbine, a method with respect to the second law of thermodynamics based on exergy analysis model is applied. The effects of heat rejection pressures, outlet temperatures of gas cooler and evaporating temperatures on the exergy loss, exergy efficiency and the coefficient of performance (COP) of the expansion turbine cycle are analyzed. It is found that the great percentages of exergy losses take place in the gas cooler and compressor. Moreover, heat rejection pressures, outlet temperatures of gas cooler and evaporating temperatures have strong influence on the exergy efficiency, COP and the exergy loss of each component. The analysis shows that there exists an optimal heat rejection pressure corresponding to the maximum exergy efficiency and COP, respectively. The results are of significance in providing theoretical basis for optimal design and the control of the transcritical carbon dioxide system with an expansion turbine.展开更多
Chlorofluorocarbons(CFCs) or hydrochlorofluorocarbons(HCFCs) are as main refrigerants used in traditional refrigeration systems driven by electricity from burning fossil fuels, which is regarded as one of the major re...Chlorofluorocarbons(CFCs) or hydrochlorofluorocarbons(HCFCs) are as main refrigerants used in traditional refrigeration systems driven by electricity from burning fossil fuels, which is regarded as one of the major reasons for ozone depletion (man-made refrigerants emission) and global warming (CO 2 emission). So people pay more and more attention to natural refrigerants and energy saving technologies. An innovative system combining CO 2 transcritical cycle with ejector cycle is proposed in this paper. The CO 2 compression sub-cycle is powered by electricity with the characteristics of relatively high temperature in the gas cooler (defined as an intercooler by the proposed system). In order to recover the waste heat, an ejector sub-cycle operating with the natural refrigerants (NH 3, H 2O) is employed. The two sub-cycles are connected by an intercooler. This combined cycle joins the advantages of the two cycles together and eliminates the disadvantages. The influences of the evaporation temperature in CO 2 compression sub-cycle, the evaporation temperature in the ejector sub-cycle, the temperature in the intercooler and the condensation temperature in the proposed system performance are discussed theoretically in this study. In addition, some unique features of the system are presented.展开更多
Cross-cultural communication mainly refers to communication between people of different cultural backgrounds. Worldwide research on intercultural communication is the rise of a new field of study in recent 30 years. W...Cross-cultural communication mainly refers to communication between people of different cultural backgrounds. Worldwide research on intercultural communication is the rise of a new field of study in recent 30 years. With the deepening of reform and opening up, China＇ s exchanges with the world are more and more frequent, China approaches to the world, and the world is also approaching the China. China should learn from the advanced experience of foreign countries, to learn all the outstanding achievements of human civilization all over the world, while the splendid Chinese culture will also be introduced to the world. In this way, it relates to the problem of cross-cultural communication.展开更多
This study provides an evaluation of China＇s growing middle class, the new consumers for world economies and estimated to be 300-500 million people. By using internal analysis of market and nonmarket variables, we de...This study provides an evaluation of China＇s growing middle class, the new consumers for world economies and estimated to be 300-500 million people. By using internal analysis of market and nonmarket variables, we detail how the future growth rate of the middle class is dependent on three issues： domestic consumption trends of Generation Y in China, the valued opportunity of the science and technology industry, and the importance of maintaining a strong work force able to increase productivity. In particular, we discuss market demands from Generation Y, products best suited for Chinese consumers, and the effect social-economic inequalities in Western China will have on development measures of the middle class. Based on data collection, interviews, library research and econometric analyses, we show how these above issues will continue to influence consumer behavior, reform policies, and the growth of the middle class in China. It is important to note that economic growth and prosperity in China will only continue if the national government and private institutions, along with the international agendas of other countries, are in balance, and not excess, of the resources and capabilities available for desired growth levels.展开更多
In this paper,exergy analysis method is developed to assess a Rankine cycle system,by using supercritical CO2 as working fluid and powered by solar energy.The proposed system consists of evacuated solar collectors,thr...In this paper,exergy analysis method is developed to assess a Rankine cycle system,by using supercritical CO2 as working fluid and powered by solar energy.The proposed system consists of evacuated solar collectors,throttling valve,high-temperature heat exchanger,low-temperature heat exchanger,and feed pump.The system is designed for utilize evacuated solar collectors to convert solar energy into mechanical energy and hence electricity.In order to investigate and estimate exergy performance of this system,the energy,entropy,exergy balances are developed for the components.The exergy destructions and exergy efficiency values of the system components are also determined.The results indicate that solar collector and high temperature heat exchanger which have low exergy efficiencies contribute the largest share to system irreversibility and should be the optimization design focus to improve system exergy effectiveness.Further,exergy analysis is a useful tool in this regard as it permits the performance of each process to be assessed and losses to be quantified.Exergy analysis results can be used in design,optimization,and improvement efforts.展开更多
In a world in which, according to public health authorities and the media, everyone seems to be getting fatter, what does fat mean when we look across cultures？ Is being fat the same in China as in the USA？ How does...In a world in which, according to public health authorities and the media, everyone seems to be getting fatter, what does fat mean when we look across cultures？ Is being fat the same in China as in the USA？ How does obesity map onto culture in a world in which there are multiple, competing models for understanding illness？展开更多
This article takes its cue from the English critic, novelist and painter John Berger. He argues that what we know determines what we see. Hotels and railway stations, though they differ in size, design and appearance,...This article takes its cue from the English critic, novelist and painter John Berger. He argues that what we know determines what we see. Hotels and railway stations, though they differ in size, design and appearance, are places of temporary national and international congress that are recognized by everyone. They become visible or even iconic once their history or their role is turned into at least part of a wider narrative in literature, film or in other arts. This provides a representative focus by which we may read a city＇s or a nation＇s past. In exemplifying such connections I focus first on the long-term history of Friedrichstraβe station and some of the surrounding hotels in the context of the history of Berlin, situating them within the national and, by implication, also the international context. Secondly, I will consider the outbreak of the First World War in 1914 as an event in which the role of railway stations generated both personal and collective memories across cultures and over several decades.展开更多
基金SupportedbytheSpecializedResearchFundfortheDoctoralProgramofHigherEducation (No .D0 2 0 0 10 5)
文摘In order to identify the locations of irreversible loss within the transcritical carbon dioxide refrigeration cycle with an expansion turbine, a method with respect to the second law of thermodynamics based on exergy analysis model is applied. The effects of heat rejection pressures, outlet temperatures of gas cooler and evaporating temperatures on the exergy loss, exergy efficiency and the coefficient of performance (COP) of the expansion turbine cycle are analyzed. It is found that the great percentages of exergy losses take place in the gas cooler and compressor. Moreover, heat rejection pressures, outlet temperatures of gas cooler and evaporating temperatures have strong influence on the exergy efficiency, COP and the exergy loss of each component. The analysis shows that there exists an optimal heat rejection pressure corresponding to the maximum exergy efficiency and COP, respectively. The results are of significance in providing theoretical basis for optimal design and the control of the transcritical carbon dioxide system with an expansion turbine.
文摘Chlorofluorocarbons(CFCs) or hydrochlorofluorocarbons(HCFCs) are as main refrigerants used in traditional refrigeration systems driven by electricity from burning fossil fuels, which is regarded as one of the major reasons for ozone depletion (man-made refrigerants emission) and global warming (CO 2 emission). So people pay more and more attention to natural refrigerants and energy saving technologies. An innovative system combining CO 2 transcritical cycle with ejector cycle is proposed in this paper. The CO 2 compression sub-cycle is powered by electricity with the characteristics of relatively high temperature in the gas cooler (defined as an intercooler by the proposed system). In order to recover the waste heat, an ejector sub-cycle operating with the natural refrigerants (NH 3, H 2O) is employed. The two sub-cycles are connected by an intercooler. This combined cycle joins the advantages of the two cycles together and eliminates the disadvantages. The influences of the evaporation temperature in CO 2 compression sub-cycle, the evaporation temperature in the ejector sub-cycle, the temperature in the intercooler and the condensation temperature in the proposed system performance are discussed theoretically in this study. In addition, some unique features of the system are presented.
文摘Cross-cultural communication mainly refers to communication between people of different cultural backgrounds. Worldwide research on intercultural communication is the rise of a new field of study in recent 30 years. With the deepening of reform and opening up, China＇ s exchanges with the world are more and more frequent, China approaches to the world, and the world is also approaching the China. China should learn from the advanced experience of foreign countries, to learn all the outstanding achievements of human civilization all over the world, while the splendid Chinese culture will also be introduced to the world. In this way, it relates to the problem of cross-cultural communication.
文摘This study provides an evaluation of China＇s growing middle class, the new consumers for world economies and estimated to be 300-500 million people. By using internal analysis of market and nonmarket variables, we detail how the future growth rate of the middle class is dependent on three issues： domestic consumption trends of Generation Y in China, the valued opportunity of the science and technology industry, and the importance of maintaining a strong work force able to increase productivity. In particular, we discuss market demands from Generation Y, products best suited for Chinese consumers, and the effect social-economic inequalities in Western China will have on development measures of the middle class. Based on data collection, interviews, library research and econometric analyses, we show how these above issues will continue to influence consumer behavior, reform policies, and the growth of the middle class in China. It is important to note that economic growth and prosperity in China will only continue if the national government and private institutions, along with the international agendas of other countries, are in balance, and not excess, of the resources and capabilities available for desired growth levels.
基金The support of the National Natural Science Founda-tion of China (50976002) is gratefully acknowledged
文摘In this paper,exergy analysis method is developed to assess a Rankine cycle system,by using supercritical CO2 as working fluid and powered by solar energy.The proposed system consists of evacuated solar collectors,throttling valve,high-temperature heat exchanger,low-temperature heat exchanger,and feed pump.The system is designed for utilize evacuated solar collectors to convert solar energy into mechanical energy and hence electricity.In order to investigate and estimate exergy performance of this system,the energy,entropy,exergy balances are developed for the components.The exergy destructions and exergy efficiency values of the system components are also determined.The results indicate that solar collector and high temperature heat exchanger which have low exergy efficiencies contribute the largest share to system irreversibility and should be the optimization design focus to improve system exergy effectiveness.Further,exergy analysis is a useful tool in this regard as it permits the performance of each process to be assessed and losses to be quantified.Exergy analysis results can be used in design,optimization,and improvement efforts.
文摘In a world in which, according to public health authorities and the media, everyone seems to be getting fatter, what does fat mean when we look across cultures？ Is being fat the same in China as in the USA？ How does obesity map onto culture in a world in which there are multiple, competing models for understanding illness？
文摘This article takes its cue from the English critic, novelist and painter John Berger. He argues that what we know determines what we see. Hotels and railway stations, though they differ in size, design and appearance, are places of temporary national and international congress that are recognized by everyone. They become visible or even iconic once their history or their role is turned into at least part of a wider narrative in literature, film or in other arts. This provides a representative focus by which we may read a city＇s or a nation＇s past. In exemplifying such connections I focus first on the long-term history of Friedrichstraβe station and some of the surrounding hotels in the context of the history of Berlin, situating them within the national and, by implication, also the international context. Secondly, I will consider the outbreak of the First World War in 1914 as an event in which the role of railway stations generated both personal and collective memories across cultures and over several decades.
