Heat Transfer Model And Experiments Of Building Indoor Air Under The Heat Storage Effects Of Ground Air Tunnels

As a green energy-saving building ventilation technology, Earth to Air Heat Exchanger System(EAHES) has been widely researched and applied at home and abroad. Early in the 1970 s, the EAHES was developing rapidly in our country, but with the economic development and wide application of air conditioning, EAHES was gradually replaced by the air-conditioning technology. In recent years, Chinese economy has a quick development, and urbanization continues to accelerate, building energy consumption caused by the same time has become even more prominent. Development of green building and building energy-saving technology has become an important subject of the common concern of the whole society, EAHES, with its energy saving, economical, and simple once again aroused the attention of domestic and foreign scholars.At present, domestic and foreign scholars have done a lot of research on the EAHES, but there is still no coupling analysis on tunnel and building in theory, and the research methods used are more confined to CFD numerical simulation and field monitoring. Based on the shortage of the previous research, this paper combined theoretical derivation and small- scale model experiment, had a further study for the first time on the coupled thermal process of EAHES.Similarity theory is the basis of small-scale model test, in this paper, the similarity of EAHES was broken down into flow similarity and heat transfer similarity, and then each part was further broken down into tunnel a nd building. The dimensionless method was applied to process dynamic differential equation and heat conduction differential equation, and derived the key similar numbers of EAHES, Reynolds number, Archimedes number, and Fourier number. A comprehensive analysis on flow similarity and heat transfer similarity was conducted, which offered a theoretical guidance for determining scales of model test and selecting experiment material.A mathematical theory model was built by physically simplifying the EAHES, and Laplace transform was applied to heat conduction differential equation, according to linear decomposition and superposition principle, the temperature was broken down into the average and the fluctuation, by substituting the two parts into heat balance equation, analytical expressions of temperature in tunnel and indoor temperature could be derived. There are always various methods in solving penetration thickness, in this paper, these methods were summarized, a more reasonable and effective formula was proposed.Based on the above analysis of the similarity theory, this paper used small-scale model experiment to study EAHES, this experiment not only took heat transfer similarity of tunnel into account, but also shortened the time scale in experiment, which was different from previous building ventilation experiments, and reflected the advantages of small-scale model experiment of EAHES. Though contrasting experimental data curve and theoretical model curve, it was proved that the mathematical analytical model of air temperature in tunnel and indoor air temperature which were derived in this paper have a high accuracy and reliability.Finally, on the derived results of the theoretical model, qualitative analysis were done for some key parameters, including depth, rad ius, length, ventilation rate, building facades and building internal thermal mass, which influence EAHES, also the annual and daily influencing trend by each factor was displayed. In a word, the quantitative calculation formula and qualitative factor analysis presented in this paper provided technical support for the design, calculation, running and operating of EAHES.