Study On Winter Ventilation Of Northern Residential Buildings And Efficient Fresh Air System With Energy Storage

With the fast economic development of C hina, residential building energy conservation and indoor air quality security and control have become the hot spot in the research area. Mechanical ventilation system are universally not installed in residential buildings in north China, and opening windows is an important way to improve indoor air quality in winter. However, its contro l and adjusting ability are poor. Considering the great indoor and outdoor temperature difference, unnecessary long time of opening window will result in serious heating loss of the residential buildings. If the air change rate cannot achieve health needs, it can be an important reason for "sick building syndrome". This paper focus on the key problem that constrain residential building ventilation in north C hina and efficient fresh air system with energy storage, and the research is able to provide scientific basis for solving the problem of winter ventilation in north China.Through the mean of network platform and on-site interviews, this paper took questionnaire survey on residents’ habit of opening window in a typical city-Shenyang in the north area. Based on the analysis and selection of a large number of samples, 500 samples on households’ opening window habit were taken as the research object. The SPSS software was used to deal with the information. This paper analyze the features of potential multiple factors that influence the residents’ opening window habit, and the independent correlations of these features and the opening window habit. O n the basis of survey and statistical analysis, rooms of different sizes of a typical residential buildings were tested with tracer gas concentration decay and other methods. The general rules of opening windows in winter and the influence of room size, direction and opening size of the window on the air change rate were discovered. Following the results of air change rate tests, some reasonable suggestions are discussed for improving the residents’ habit of opening windows.The mathematical model of thermal process of opening windows in winter was established. Calculating program was compiled in the Matlab software to solve the model. During the establishment of the model, mixing coefficient formula for single sided ventilation was put forward based on the tested data. Then the empirical model proposed by Warren was revised. Using large amount of tested data, the temperature decreasing rule for indoor surfaces were acquired. Several common opening window condition in winter were analyzed using the mathematical model, and the AC R change rules were discovered for conditions with different opening window sizes, initial indoor air temperatures and outdoor temperatures. Taking the tested room as prototype, the physical model of room and outside wind space was established. The CFD method was used to simulate the winter window ventilated room and transient heat transfer pro cess of the outside world. The achieved temperature field and velocity field were helpful to intuitive analysis of flow and heat transfer characteristics of opening window ventilation characterized by single sided ventilation.The simplified mathematical analysis model of solar fresh air collector was established, and then the factors that were helpful for improving the thermal efficiency of the solar fresh air collector were discussed. A kind of solar air collector was experimentally established. Highly e fficient solar fresh air system was established based on the coupled integration of macro-capsulation of PCM, immersing float stones for higher thermal conductivity, using heat pipes for efficient thermal energy storage and the S channel. Different programs were arranged in the DSC test platform to test the selected PCM, and more precise phase change range, latent heat were achieved. Multiple working condition test comparisons and analysis were arranged for solar fresh air collector. Practical efficient methods were acquired for elevating the thermal efficiency of the solar fresh air collector. After testing the highly efficient solar fresh air system with coupled integration, there were presented in truth that the heat pipe helps for elevating the thermal e fficiency and the thermal exchange and storage device with phase change energy storage is beneficial for extending the providing time of heated fresh air. For the problem that the thermal releasing effect of the thermal exchange and storage device, numerical simulation method was used to optimize the geometry by shorten the size of flow channel and minimizing the thickness of phase change energy storage blocks.The research revealed that opening window habits of the northern residents were unreasonable and the natural ACR is seriously insufficient. Hence, the residents need to decrease the opening window time for one time and increase the frequency of opening windows in a day. There is a significant correlation between subjective awareness of indoor air quality and the health consciousness of residents and the opening window habit. The predicted values in the Matlab simulation program is basically consistent to the experimental value. It reflects the correctness of theoretical thoughts(modified single sided ventilation formula, the wall temperature degradation formula etc.) The process rules for ventilation in winter was obviously different with the summer condition, and it showed transient characteristics of a rapid decline and slowly decreasing. Under the experimental conditions, the influence of room size on the ACR was more evident than the window opening size, wind direction, indoor initial temperature and outdoor temperature. The highest thermal efficiency of the optimized solar fresh air collector reached 55.3% when the outside temperature is around 0℃. With the help of heat pipe, the thermal efficiency of the collector increased by 6.9%, while the extending time of supplying the fresh air is 4.5h after using the thermal exchange and storage device with phase change energy storage. The effect of phase change energy storage module thickness reduction was more apparent and the highest effective heat release rate was 85.2% in the optimization scheme.The fruits of this paper could play positive role for building energy efficiency of north China and indoor air quality security.