| Building exterior surface heat transfer coefficient is an important parameter not only for energy consumption analysis, but also for urban wind environment and thermal environment simulation. It is of great significance for indoor and outdoor thermal comfort, as well as other issues such as urban heat island effect. Nowadays, in many countries all over the world, the outer surface of total heat transfer coefficient used in thermal calculation was a fixed value, though we know it contains several subentries and each one should be a variable in truth, very little researches regarding their dynamic changes, especially under the presence of evaporation.Evaporative heat transfer phenomenon is common in nature. For porous building materials, after rainfall, under the combined effect of climatic conditions, evaporation occurs with different intensities. It can bring cooling effect and the heat transfer of materials is different from dry state. Therefore, research on porous building materials’surface heat transfer coefficient in the process of evaporation has an important theoretical and practical significance for building energy efficiency, and this paper will study it with hot-humid climatic wind tunnel.The full text mainly contains two aspects: First, improve wind-tunnel control system and evaluate its accuracy. Second, proposed a dynamic wind-tunnel experimental method of exterior surface heat transfer coefficients and carried out experimental study.First, based on the status of hot-humid climatic wind tunnel, developed independently an integrated intelligent control system, so as to achieve a better simulation of the outdoor climate as well as intelligent operation and dynamic display of measurement parameters. The console could real-time display the controlled equipments’running situation in the form of animation, and dynamic describe the measured parameters’changing curves which updated per second, and also automatically collected and calculated results, so it was a high-precision automatic control system.For the new integrated system, it is necessary to evaluate its control accuracy. According to the actual situation of wind tunnel, drew lessons from the latest methods of non-statistical uncertainty, selected respectively gray theory method and large samples entropy method to assess dynamic control conditions that covering full control range of system and the corresponding steady-state control conditions, and gave the specific control precision for each condition. The results showed that for dynamic control ofⅠ~Ⅴclimatic regionalization for architecture, except for maximum deviation and data dispersion in temperature control were greater, the relative humidity, solar radiation intensity and wind speed control have been all reached high precision, on the other hand, though we could still get higher accuracy in relative humidity and solar radiation intensity in all steady-state conditions, the fluctuations of high temperature and low wind-speed conditions and maximum deviation of high temperature control were relatively larger. Overall, wind tunnel has achieved reproduction ability of outdoor dynamic weather conditions and subsequent experimental studies could be carried out.Using hot-humid climatic wind tunnel, proposed an experimental method of porous building materials’exterior surface heat transfer coefficients in the process of evaporation. Based on one-dimensional dynamic heat and moisture transfer principle, introduced porous soil heat flux sensor in wind tunnel and established heat balance equation of outer surface, then according to Newton’s law of cooling, the hourly dynamic value of heat transfer coefficient of evaporation, radiation and convection could be calculated. This method is an exploration of dynamic test method about materials’physical parameters in the process of coupled heat and mass transfer, so it could be expected this would provide a convenient and practical research method for related issues in the field of building thermal.Chose three porous building materials, which were permeable pavement brick, sedum-soil light roll roofing and porous exterior wall tile material, controlled wind tunnel to simulate summer typical meteorological environment of different climatic regionalization for architecture, a series of experimental tests were carried out. By horizontal and vertical comparison, it was analyzed and summarized the variation regularity of each exterior surface heat exchange and the interaction and relationship between them during evaporation, and also provided the daily and hourly averages of evaporation, convection and radiation heat transfer coefficients. |
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