مقایسه عملکرد حرارتی درختان پهن‌برگ و سوزنی برگ در دره‌های شهری- مورد پژوهشی: مناطق شهر اصفهان

نوع مقاله : مقاله پژوهشی (کاربردی)

نویسنده

کارشناسی ارشد، عضو هیات علمی، گروه ساختمان و معماری، دانشگاه فنی حرفه‌ای، تهران، ایران.

10.48301/kssa.2022.298183.1650

چکیده

با رشد شهرنشینی و افزایش تراکم ساختمان‌ها، دره‌های شهری به وجود می‌آیند که ازنظر آلودگی و درجه حرارت با مشکلات بیشتری روبرو هستند. تنش‌های حرارتی شدید در این دره‌ها میزان رضایتمندی حرارتی عابران را کاهش داده است.پوشش گیاهی یکی از راهکاری مهم در جهت کاهش دمای هوا و بهبود آسایش حرارتی به‌خصوص در پیاده‌روها است. پوشش گیاهی در فرم‌های مختلف با سایه‌اندازی و یا سرمایش تبخیری به بهبود شرایط دمایی محیط کمک می‌کند. بررسی‌های انجام‌گرفته در شهر اصفهان نشان می‌دهد که درخت پرتکرارترین نوع پوشش گیاهی در دره‌های شهر اصفهان است از طرفی درختان به‌واسطه مشخصاتی مانند LAD و LAI، نوع برگ (پهن یا سوزنی) و برگ‌ریز بودن یا همیشه‌سبز بودن شرایط حرارتی متفاوتی در معبر ایجاد می‌کنند. هدف این تحقیق بررسی تفاوت تأثیرگذاری حرارتی میان‌پر تکرارترین نوع درخت پهن‌برگ با پرتکرارترین نوع درخت سوزنی‌برگ در دره‌های شهری اصفهان با نسبت H/W و جهت‌گیری‌های متفاوت است. برای بررسی میزان تأثیرگذاری درختان با ویژگی‌های متفاوت در دره‌های شهری از نرم‌افزار Envi-met v4.1 استفاده‌شده است. در گام اول با بررسی میدانی شرایط دره‌های شهری و پوشش گیاهی‌های پرتکرار در محیط مشخص شد سپس با شبیه‌سازی با نرم‌افزار ذکرشده به بررسی و مقایسه میان شرایط حرارتی ایجادشده در فصل تابستان و زمستان در دره‌های شهری پرداخته‌شده است. نتایج تحقیق حاکی از آن است درختان پهن‌برگ (برگ‌ریز) در تابستان در هر چهار جهت‌گیری عملکرد بهتر داشته‌اند و pmv را حداکثر 5/2 واحد کاهش داده‌اند. در زمستان درختان سوزنی‌برگ (همیشه‌سبز) به‌واسطه محافظت معابر از باد سرد زمستانی شرایط آسایش بهتری بر اساس شاخص pmv فراهم کرده است. این بهبود حداکثر 3/0 واحد بوده است؛ اما درمجموع تابستان و زمستان درختان برگ‌ریز بهترین شرایط آسایش حرارتی را مهیا کرده‌اند. ازاین‌رو پیشنهاد می‌شود در شهر اصفهان خصوصاً در نقاط پرتراکم مانند دره‌های شهری عمیق و باریک از کاشت درختان سوزنی‌برگ خودداری شود و تنها در معابر رو به باد در فصل زمستان مانند جهت‌گیری شرقی- غربی و شمال شرقی- جنوب غربی در ابتدای معابر، درختان سوزنی‌برگ جهت کنترل سرعت و شدت باد زمستانی کاشت شود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Comparison of Thermal Performance of Broadleaf and Coniferous Trees in Urban Canyons (Case Study: City of Isfahan)

نویسنده [English]

  • Tahereh Koulivand
MSc Faculty Member, Department of Architectural and Building, Technical and Vocational University (TVU), Tehran, Iran.
چکیده [English]

With the growth of urbanization and the increase in the density of buildings, emerging urban valleys face greater problems in terms of pollution and temperature. Severe thermal stresses in these valleys have reduced the level of thermal satisfaction of passers-by. Planting vegetation is one important method of reducing air temperature and improving thermal comfort, particularly on sidewalks. Shading or evaporative cooling helps to improve ambient temperature conditions. Studies conducted in Isfahan show that trees are the most repetitive type of vegetation in the valleys of Isfahan. They create different thermal conditions in the passage. The purpose of this study was to investigate the difference in thermal impact between the most common type of broadleaf tree and the most frequent type of coniferous tree in the urban valleys of Isfahan with different H / W ratio and orientation. Envi-met v4.1 software was used to evaluate the impact of trees with different characteristics in urban valleys. First, through field study, the conditions of urban valleys and recurrent vegetation in the environment were determined. Then, by simulation with the mentioned software, the thermal conditions created in summer and winter in urban valleys were studied and compared. The results show that broadleaf (deciduous) trees performed better under all four directions in summer and reduced pmv by a maximum of 2.5 units. In winter, coniferous (evergreen) trees protect the passages from the wind. The winter cold provided better comfort conditions based on the pmv index. Conditions were improved by a maximum of 0.3 units. However, in general, summer and winter deciduous trees provided the best conditions for thermal comfort. It is recommended that in the city of Isfahan, particularly in densely populated areas such as deep and narrow urban valleys, and on windy roads in winter (with east-west and northeast-south direction) conifers and leaf trees be planted. At the start of passages, conifers should be planted to control the speed and intensity of winter winds.

کلیدواژه‌ها [English]

  • Vegetation Thermal comfort Urban canyons Hot and dry climates Envi
  • met
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