بررسی جریان هوا و انتقال حرارت در نمای تهویه شده با درز باز مطالعۀ موردی: ساختمان اداری شهر اصفهان

نوع مقاله : مقاله پژوهشی

نویسندگان

1 کارشناس ارشد مرکز تحقیقات افق‌های نوین در معماری و شهرسازی، واحد نجف‌آباد، دانشگاه آزاد اسلامی، نجف‌آباد، ایران

2 استادیار مرکز تحقیقات افق‌های نوین در معماری و شهرسازی، واحد نجف‌آباد، دانشگاه آزاد اسلامی، نجف‌آباد، ایران

چکیده

اهداف و پیشینه: در پیشینۀ این پژوهش به ضرورت استفاده از سیستم‌های نوین نماسازی، به‌ویژه نماهای تهویه‌شده با درز باز، به‌منظور بهینه‌سازی مصرف انرژی در ساختمان‌ها پرداخته شده؛ چراکه در مطالعات بین‌المللی، به‌ویژه در اقلیم‌های مدیترانه‌ای، به‌طور گسترده‌ای بر اثربخشی این نماها در کاهش بار حرارتی و بهبود تهویۀ طبیعی تأکید گردیده است، اما در ایران، به‌ویژه در اقلیم گرم و خشک، آنچه مشاهده می‌شود، پژوهش‌های محدود و ناقصی در این زمینه است. هدف اصلی در این مطالعه، بررسی تأثیر درصد پوشش نمای تهویه‌شده، ضخامت لایۀ هوای بین دو پوسته و ارتفاع نصب نما بر جریان هوا، دمای سطح داخلی، و مصرف انرژی ساختمان‌های اداری در شهر اصفهان است. در این پژوهش تلاش شده تا با تکیه بر شبیه‌سازی عددی و تحلیل حساسیت، الگویی بهینه برای طراحی نمای دوپوسته در شرایط اقلیمی ایران عرضه گردد.
 
مواد و روشها: در این پژوهش با رویکردی کمّی و ماهیتی کاربردی، با استفاده از شبیه‌سازی عددی، عملکرد حرارتی و جریان هوای نمای تهویه‌شده با درز باز در یک ساختمان اداری واقع در اقلیم گرم و خشک اصفهان بررسی شده است. برای این منظور، از نرم‌افزار انسیس فلوئنت برای تحلیل دینامیک سیالات (CFD) و از طراحی بیلدر برای محاسبۀ مصرف انرژی استفاده شد. مدل پایه شامل ساختمانی 8 طبقه با نمای جنوبی مجهز به صفحات سرامیکی مدولار با درز باز بود که در 6 حالت درصد پوشش (از 0 تا 100٪)، دو ضخامت حفره (4 و 6 سانتی‌متر)، و سه ارتفاع مختلف (طبقات همکف، چهارم، و هشتم) تحلیل شد. نتایج شبیه‌سازی در دو بازۀ زمانی انقلاب تابستانی و زمستانی بررسی و با تحلیل حساسیت، تأثیر هر متغیر مستقل بر متغیرهای وابسته‌ای چون سرعت جریان هوا، دمای سطح داخلی، شار حرارتی، و مصرف انرژی ارزیابی شد.
 
نتایج و جمعبندی: نتایج پژوهش نشان داد که نمای تهویه‌شده با درز باز در اقلیم گرم و خشک اصفهان، درصورت طراحی بهینه، تأثیر چشمگیری در بهبود عملکرد حرارتی و کاهش مصرف انرژی ساختمان‌های اداری دارد. در حالت بهینه، یعنی با پوشش 60 تا 80درصدی نما و ضخامت لایۀ هوای 6 سانتی‌متر و نصب در طبقۀ چهارم، سرعت جریان هوا به محدودۀ مطلوب برای تهویۀ طبیعی رسید و دمای سطح داخلی نما کاهش یافت. همچنین، شار حرارتی در تابستان تا بیش از 50٪ کاهش و مصرف انرژی نسبت به نمای معمولی تا 46٪ در تابستان و 50٪ در زمستان صرفه‌جویی را نشان داد. تحلیل حساسیت نیز بیانگر آن بود که ارتفاع نصب نما، سطح پوشانندگی، و ضخامت لایۀ هوا به‌ترتیب بیشترین تأثیر را بر عملکرد نما دارند؛ بنابراین استفاده از این نوع نما، به‌ویژه در ساختمان‌های اداری دولتی در اقلیم‌های گرم ایران، توصیه می‌شود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigating Air Flow and Heat Transfer in An Open-Joint Ventilated Façade; The case of an Office Building in Isfahan

نویسندگان [English]

  • Najmeh Malekipour 1
  • Narges Dehghan 2
1 M.A. Advancement in Architecture and Urban Planning Research Center, Na.C., Islamic Azad University, Najafabad, Iran
2 Assistant Professor, Advancement in Architecture and Urban Planning Research Center, Na.C., Islamic Azad University, Najafabad, Iran
چکیده [English]

In Iran, energy consumption in office and government buildings is higher than in other buildings, and the envelope of these buildings, as the first layer in dealing with environmental conditions, is critical to energy efficiency. In addition to providing thermal comfort, the building envelope can reduce energy consumption for heating, cooling, and ventilation. The greatest strategy for a building's envelope is a ventilated façade. A layer of air is placed between the outer layer of the façade and the building's wall, and this gap is naturally or mechanically ventilated. The term "open joint ventilated façade" refers to a type of ventilated facade in which the outer layer is made up of spaced slabs (open joint). Because of the solar chimney effect, these joints allow outside air to enter the chamber and provide natural ventilation. The purpose of this study is to investigate the thermal behavior and air flow in open joint ventilated facades on the southern front of an office building in the hot and dry climates of Isfahan, based on global research on this facade, which is mostly done in Spain and the existence of research weaknesses in Iran. The surface of this type of façade compared to a traditional one, and the thickness of the air layer between the two layers, are independent variables for this purpose. Furthermore, this type of facade was investigated in three different height modes (ground floor, fourth and eighth floor). During the summer and winter solstices, the simulation in this paper was run using the computational fluid dynamics approach using Fluent software. In comparison to other modes, the results showed that 60 percent and 80 percent of the surfaces of open joint ventilated facades on the fourth story with a 6 cm air layer thickness have the best performance in the southern front.

کلیدواژه‌ها [English]

  • Open-joint ventilated façade
  • Energy saving
  • Building envelope
  • Heat transfer
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