【作者】 张佩东；

【导师】 赵蕾；

【作者基本信息】 西安建筑科技大学 ， 供热、供燃气、通风及空调工程， 2008， 硕士

【摘要】 随着经济的发展和人们生活水平的提高,空调得到越来越广的应用,且人们对空调室内环境的舒适性、室内空气品质以及能耗问题也越来越关注。辐射供冷与置换通风结合的复合空调是一种经济、节能、舒适性好的空调系统形式,而逐渐得到研究和应用。本文首先分析总结复合空调的热、湿环境控制指标,在利用已有实验结果验证CFD数值仿真结果的基础上,讨论了网格划分密集程度对模拟结果的影响;然后对室内冷顶板的传热过程建立了数学模型,分析了各结构参数对冷顶板供冷能力以及表面温度均匀性的影响,进一步通过数值仿真结果显示了顶板表面温度分布均匀性对室内热环境的影响。由于供冷参数的不同组合会导致置换通风与辐射冷板复合空调室内热湿环境及系统运行费用的不同,因此本文接着利用正交法设计了5因素5水平实验方案,模拟分析了各供冷参数与热舒适性指标PMV的相关性,通过级差法和方差分析法得出了送风温度、速度及相对湿度、冷板表面温度及冷板与天花板面积比等参数对室内热舒适影响作用强弱的先后顺序和最佳组合供冷参数;然后,就对舒适性影响最显著的因素—送风速度的变化所引起的室内热环境的变化过程进行了动态模拟,分析了室内工作区和非工作区温、湿度随时间的变化规律,表明室内热湿状况再次达到稳态所需的响应时间长,但是,冷顶板表面出现结露的可能性也很小。故对置换通风-辐射供冷复合空调系统不建议采用变风量调节的方案。这一结论可为复合空调系统设计参数的确定以及运行调节方案的制定提供指导。最后在最佳组合工况的基础上,以西安地区的室外气象条件以及两种常用墙体的结构和物理特性为准,通过调节辐射冷顶板的供冷面积对办公室从上午8:00到下午18:00的室内环境进行了模拟,得出了不同时刻的优化控制方案。分析了不同外墙结构类型和辐射冷顶板开启模式对室内PMV均匀性以及外墙内表面温度分布的影响。更多还原

【Abstract】 Along with the development of economy and the enhancement of people’s living standard, energy consumption of air-conditioning systems increases unceasingly. Though air-conditioning system has already been used very widely, more and more attention is paid to indoor thermal comfort and indoor quality it can produce and its energy consumption problems.Hybrid system of radiant cooling and displacement ventilation becomes adopted gradually in practical project and arouses wide research interest for it can provide better thermal environment more energy efficiently.Firstly, comfort indoor indexes were summarized. CFD simulation results based on indoor zero-equation turbulence model were validated using experimental data. Then, the effect of the number of grids on simulation result was investigated. And then a steady state mathematic model of a chilled panel was established and the effect of the structural parameters on surface temperatue distribution and cooling capacity of chilled panel was analyzed. The influence of panel temperature evenness on indoor thermal environment simulation result was also discussed. It is found that it has little infulence on thermal comfort in occupied zone.Choosing proper combined cooling parameters is an important step in designing hybrid air-conditioning systems of chilled ceiling panel and displacement ventilation. Different combination may bring about different indoor thermal comfort as well as different operational cost. A set of optimal combined cooling parameters were proposed by conducting 5 factors, 5 levels simulation experiments arranged by.orthogonal test design method. Under the optimal condition, the PMV value reaches zero with 5% PPD and ventilation efficiency obtain relatively high value. The individual influence of such cooling parameters as supply air flow rate, temperature and relative humidity of DV, the surface temperature of CP and the area ratio of CP to the ceiling on PMV value were studied by analysis range method and analysis of variance method. Results indicate that hybrid air-conditioning pattern can achieve the best indoor thermal environment in one among all simulation experiments. And the dynamic responses of room air to the change in supply air flow rate, which has the strongest influence on PMV, were simulated. It is analyzed how the air average temeperature and relative humidity in the occupied zone and non-occupied zone change along with time after the change in supply air flow rate was exerted. It reveals it will take about 20 minutes for the indoor air temperature to approach another steady value. And the air layer temperature just below the celing panel was higher than that of occupied zone. The dew point of the air layer is higher than the surface temperature of the chilled ceiling panel. It indicates that the possiblity of dew occur on the chilled ceiling panel is very less.Finally, the boundary condition of the external wall was specified using hourly outdoor air temperature in a typical day of Xian and using thermal properties of two types of wall structure normally used. When the optimal combination of supply air temperature, flowrate and surface temperature of the chilled panel was adopted, the best area ratio of the chilled ceiling panel to that of the ceiling was selected through simulations. The best values of the hourly area ratio of chilled panel were determined for a typical office from 8:00 A.M. to 6:00 P.M. With these cooling parameters, PMV values of the occupied zone can remain within the accepted range, -0.5 to o.5. The influence of the external wall structure and the area ratio of the chilled ceiling panel on internal surface temperature of the exterior wall and indoor PMV values were also analyzed.更多还原