پیشنهاد روشی برای پهنه‌بندی اقلیمی ایران بر مبنای پتانسیل تهویه طبیعی (مطالعه موردی شهر یزد)

تقسیم بندی اقلیمی یکی از ابزارهای مفید در سازماندهی اطلاعات مختلف در شرایط مشابه است. تاکنون انواع مختلفی از تقسیم بندی های اقلیمی با اهداف متفاوت بر گستره کشور ایران پیشنهاد شده است. در زمینه طراحی ساختمان، وجود تقسیم بندی های مناسب با اهداف معماری، نقش مهمی در ایجاد ساختمان های منطبق با شرایط اقلیمی و میزان بهینه مصرف انرژی ایفا می­کند. این مقاله با بررسی تقسیم بندی های اقلیمی موجود به تحلیل کارایی و کاستی های هر سیستم در طراحی ساختمان و معماری پرداخته است. از جمله این کاستی‌ها می توان به عدم توجه به تفاوت در محدوده آسایش حرارتی و میزان نیروهای محرکه باد در مناطق مختلف اشاره کرد. در نهایت با توجه به کاستی های موجود در سیستم های ذکر شده، روشی جهت پهنه بندی جدید اقلیمی ایران بر اساس پتانسیل تهویه طبیعی پیشنهاد گردیده است. بدین منظور اتاقی از یک ساختمان اداری در شهر یزد با ویژگی های متداول ساخت، ابعاد و مصالح با استفاده از نرم افزار انرژی پلاس شبیه سازی شده و در دو ماه آوریل و ژوئیه، به عنوان دو ماه نمونه با شرایط دمایی به ترتیب معتدل و گرم مورد بررسی قرار گرفته است. مقایسه تطبیقی رفتار حرارتی ساختمان در چهار حالت بدون تهویه، تهویه روزانه، تهویه شبانه و تهویه روز و شب بهترین استراتژی تهویه ومیزان آن را در هر ماه نشان می دهد. به این ترتیب با انجام شبیه سازی های مشابه، در سایر شهرها می­توان بر اساس نوع تهویه و میزان آن (پتانسیل تهویه) به دسته بندی شهرهای مشابه پرداخت. چنین تقسیم بندی با ارائه تصویری مطابق از پتانسیل های موجود با واقعیت، رهنمودهایی مفید را برای معماران، جهت طراحی ساختمانی با بهره مندی از تهویه طبیعی و با حداقل نیاز به سیستم های سرمایش و گرمایش مکانیکی، فراهم می نماید.

New Method for Climatic Classification of Iran Based on Natural Ventilation Potential (Case study: Yazd)

IntroductionClimatic classification is one of the most useful methods in arrangement of information for similar places. Until now various kinds of climatic classification systems have been proposed for Iran concerning different goals. Buildings are affected by climatic situations in many ways. Due to this suitable recognition of climatic characteristics related to building design is essential. In this article assessing benefits of each climatic classification system for building design and architecture, defections of these systems have been noticed. Ignoring differences in thermal comfort zone and wind forces in various places are some of these defections. One of the most useful classifications for building design purpose is the HDDCDD system proposed by Khalili. This system is based on the thermal comfort condition in airconditioned buildings, ignoring natural ventilation potential. Depending on wind forces, natural ventilation could have significant effect on thermal comfort and though reduction of airconditioning systems usage and energy consumption. According to these, a new method has been proposed for Iran climatic classification based on natural ventilation potential and different thermal comfort zone. Materials and MethodsA typical office room in Yazd has been modeled for two months, April and July as moderate and hot month. An energy simulation program called Energy Plus was utilized to simulate the building thermal behavior. The required weather data had been derived from the Typical Meteorological Year (TMY) weather data used in EnergyPlus (EPW) weather file format. The simulations have been setup in four ventilation scenarios for each month: day ventilation, night ventilation, day and night ventilation and without ventilation. The results show thermal behavior of the simulated building affected by climatic parameters. The building also is taking advantages of natural ventilation potential which depends on wind speed and direction. ResultsThe results show day and night ventilation as the best choice of ventilation. The acquired results determine the ventilation potential to keep building indoor temperatures within thermal comfort zone. In this method, factors of weather data in conjunction with natural ventilation potential characterize the place. This method is based on the HDDCDD values according to the specific thermal comfort zone for each place.The values for CDD in April have been decreased from 7856.88 to 6.68, with no ventilation and day and night ventilation, respectively. In June the reduction was from 13285.97 to 348.81. This means that using natural ventilation could decrease energy consumption of the building effectively. Accordingly the CDD value for each city would be different using various kinds of natural ventilation. A new climatic classification would be achieved by defining cities with similar CDD value and ventilation scenario. These values represent the natural ventilation potential of cities which depends on local wind forces. ConclusionAccording to various goals and distinction factors, a climatic classification system would be useful for special purpose. Only some of the climatic classification systems are created in conjunction with building design. A new method has been proposed for Iran climatic classification based on natural ventilation potential and different thermal comfort zone. A typical office room in Yazd has been modeled as the sle to evaluate the proposed method. Simulations have been setup for two months in four ventilation scenarios: day ventilation, night ventilation, day and night ventilation and without ventilation. The reduction in CDD values is various using each ventilation scenarios. On the other hand the values for each city would be different according to various climatic parameters. The resulted values for HDDCDD and natural ventilation potential show the best choice for ventilation. These values are the basic parameters to create the new climatic classification system based on natural ventilation potential proposed in this article. Applying similar simulations for other cities, it is possible to classify them based on values for natural ventilation potential and its type. Cities with similar CDD value and ventilation scenario would be in the same climatic zone. This method will consider available resources for wind as well as other climatic factors for selected city and also thermal comfort zone suitable for naturally ventilated buildings. Such classification will provide useful guidelines for architects to design naturally ventilated buildings with minimum need for mechanical cooling devices.