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Energy Efficiency Evaluation of Especial Type of Iranian Residential Building with Vast Western and Eastern Wall

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【Author in Chinese】 Masoud Taheri Shahraein

【Supervisor】 孟庆林赵立华

【Author's Information】 华南理工大学, 建筑技术科学, 2010, 博士


【Abstract in Chinese】 建筑围护结构的热工性能是建筑能耗的重要影响因素之一。研究通过围护结构的热损失对于节能建筑的设计非常重要。过去二十年中,位于单层平房之间的多层住宅在伊朗的大城市中(例如马什哈德)不断发展。该建筑的墙体材料为热性能较差的粘土空心砌块,在马什哈德地区,90%以上的建材是这种粘土空心砌块。而且按照伊朗穆斯林的建筑设计规则,不能从这种类型的建筑里看到位于其东西侧的单层平房。因此,这种住宅的东西外墙没有窗户,建筑平均窗墙面积比在0.1~0.2之间。本文主要研究伊朗穆斯林居住建筑的东西外墙对建筑能耗的影响,对此多层建筑的墙体传热进行了全面研究,分析了建筑能耗的不同影响因素以及各种建筑节能方法的可能性。重点讨论了用新墙体构造(采用保温材料)代替伊朗穆斯林建筑原墙体构造(粘土空心砌块墙)后对减少建筑能耗的作用。为此,采用模拟和现场实测相结合的方法对伊朗马什哈德两栋不同墙体构造(一栋为普通构造,一栋为改进构造)的住宅能耗进行研究。做了以下工作:1)比较两种类型住宅的热工性能,采用CFD软件PHOENICS模拟了间歇空调+自然通风工况下建筑周围及室内的风速,并确定了夏季自然通风条件下房间的通风换气次数(ACR)。室内风速分布模拟结果显示:室内大部分区域(约95%)为舒适区,通风换气次数(ACR)可达23次/小时。2)采用实验室测量(热箱法)和软件模拟(K-Value,Therm-6)的方法对墙体进行研究,模拟及实测结果显示:用改进墙体替代原墙体后,墙体热流分别减少了59%和45%,“延迟时间”和“衰减倍数”的实测与模拟结果吻合较好。3)还利用全年动态能耗模拟软件DeST-h对两种类型的住宅能耗进行了模拟,以评价不同因素对建筑空调采暖能耗的影响。模拟结果表明:采用自然通风可减少80-90%的空调运行时间;普通建筑能量损失的主要途径是东墙、西墙、屋顶和地面,分别占总能耗的19%、18%、14%和7%。4)将马什哈德两栋实际建筑的能耗及墙体热流实测值(分为长期和短期)进行比较得出:普通住宅的能耗比改进住宅多43%,且普通住宅的东西外墙热流比改进住宅高94%。5)对住宅采暖空调能耗模拟值与实测值进行分析,两者较为一致。模拟与实测结果显示:建筑空调负荷分别减少29%和24%,建筑采暖负荷分别减少34%和30%,说明用改进墙体替代原墙体可显著减少建筑能耗。综上所述,由于改进墙体与原墙体的施工工期和成本相似,而改进墙体有利于建筑节能。因此对于本文所研究的居住建筑类型,在不增加成本的前提下,采用新的保温墙体构造替代原墙体可减少能源需求,是迈向可持续建筑的重要一步。

【Abstract】 The building envelope is one of the most important systems affecting energy efficiency of a building. Comprehensive analyses and researches of heat loss through the envelope are vital for design of energy efficient buildings. Generally, it is regarded that heat is mainly lost by conduction. In addition, the gradient between indoor and outdoor temperatures highly influences the energy consumption in the arid regions.Influence of western and eastern walls in energy consumption of especial residential buildings have been investigated in this study. Mentioned type of mid-rise residential buildings has evolved in the big cities of Iran (such as Mashad) over last two decades and located between one story houses. Every years more than 90% of new constructed residential buildings applying hollow clay blocks with poor thermal properties for exterior walls in Mashad. According to the Iranian Islamic architectural rules, these apartments cannot have any view to the one-story houses, which are located in their neighborhood (eastern and western parts of apartment). Hence, these apartments have no window on their vast eastern and western walls and the average of window to wall ratio in these apartments is around 10-20 percent. Here, a comprehensive research has been performed on heat transfer through the walls of mid-rise residential buildings, to investigate the impact of different factors and possibility of performing various approaches on reduction of energy consumption in the mentioned buildings. In this case, the effects of a suggested construction method using insulation materials instead of conventional construction method (hollow clay block wall) on decreasing the consumed energy of the walls were studied. For this purpose, two apartments with different construction methods (conventional and suggested methods) of walls are selected in Mashad-Iran and the amount of energy consumption in these apartments were investigated by simulation and in situ measurement methods. To investigate the behavior of these apartments, CFD software PHOENICS was applied to simulate wind velocity around and inside the building in intermittent air conditioning with natural ventilation and determine the amount of ACR of building in natural ventilation condition during summer. The simulations on wind velocity distribution inside of buildings exhibited that most of apartment area (about 95%) was comfortable zone, and ACR was reach up 23 times per hour. In addition, building walls were investigated by simulation software (e.g. K-Value and Therm-6) and laboratory measurements (by Hot Box). The results of simulation and measurements showed that applying suggested wall instead of conventional wall reduced about 59% and 45% of heat fluxed through wall, respectively. The evaluation also showed good similarity for results of “time lag”and“decrement factor”by simulation and measurement methods. In addition, two studied apartments were simulated by DeST-h (annual dynamic energy simulation software) to evaluate the effects of various factors on the building cooling-heating loads. The results of indoor temperature of studied buildings indicated applying natural ventilation could decrease about 80-90% of requirement time for air-conditioning during summer. The results also implied that the important factors in the energy loss in the conventional building are eastern wall, western wall, roof and floor, and their shares for energy consumption are about 19, 18, 14 and 7%, respectively. To approach real condition, in situ measurements are performed on two full-scale apartments in Mashad. Therefore, the amount of energy consumption and heat flux through wall in these apartments during long and short terms in-situ measurements were determined and the results were evaluated. The evaluations indicated that not only total energy consumption of conventional apartment were 43% more than suggested apartment, but also total heat flux through western and eastern wall of conventional apartment was 94% more than suggested apartment. Finally, simulation and measurement methods showed good similarity in case of cooling and heating loads and indicated applying suggested wall instead of conventional decreases energy consumption of studied buildings. The results of cooling loads showed about of 29, 24% reduction, and results of heating loads present about of 34, 30% reduction for simulation and measurement methods, respectively.In general, due to similar construction time and cost of conventional and suggested walls and the impact of suggested walls on improvement of energy conservation of residential buildings, applying the new insulated wall is one step toward sustainable building hence the developed construction method has merit to be replaced with conventional method for the studied residential buildings to reduce energy demand with constant cost.

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