تأثير فرم بر ميزان سايه‌اندازي و جذب حرارت در گنبد آب‌انبارهاي يزد

Effect of Form on Shading amount and heat Absorption in Domes of YAZD AB ANBARS

آب ­انبارها بناهايي بودند كه اكثراً در مناطق گرم و خشك كشور براي خنك نگه­ داشتن آب در طول سال مورد استفاده مردم قرار مي ­گرفتند. يكي از اصلي ­ترين عنصر آب‌انبارها پوشش مخزن مي­ باشد كه از طاق­ هاي آجري گوناگوني مانند آهنگ، كلنبو با خيز و فرم­هاي متفاوت در ساخت آنها استفاده شده است. هدف از اين پژوهش شناخت ميزان دريافت تابش خورشيد و سايه ­اندازي در گنبد آب­انبارهاي يزد مي ­باشد كه منجر به شناخت بهينه ­ترين پوشش مخزن آب‌انبار در بين نمونه­ هاي مطالعه شده مي­ گردد. براي انجام اين تحقيق پنج نمونه از آب‌انبارها با ساختار متفاوت گنبد در شهر يزد انتخاب گرديد و ميزان دريافت تابش ساليانه آن­ها در گرم­ترين روز سال، در ساعات 14، 16و 18 با استفاده از تحليل انرژي‌پلاس نرم‌افزار راينو تحت پلاگين­هاي هاني‌بي و ليدي باگ انجام گرفت. نتايج آناليزها نشان مي­دهد؛ با افزايش سطوح گنبدها ميزان جذب حرارت در محدوده در معرض تابش و در محدوده سايه بيشتر مي­شود. در هنگام طلوع و غروب خورشيد مقدار دريافت تابش تقريباً در تمام گنبدها شبيه هم است، ولي هنگام ظهر؛ جذب حرارت گنبدهاي با خيز بلند و سطح تماس كم نسبت به تابش خورشيد؛ كمتر از گنبدهاي با خيز كم و سطح تماس زياد است؛ كه علت اصلي آن ايجاد سايه بيشتر و جذب حرارت كمتر در اين نوع گنبدها مي ­باشد. بيشترين دريافت حرارت در ساعت 14 مربوط به گنبد برسويه تفت (kwh/m2 128187) با خيز كم و كمترين دريافت حرارت در حاج قاضي يزد با خيز بلند و سطح تماس كم (kwh/m2 80753) است. رابطه­ ي بين خيز طاق گنبد با ميزان دريافت تابش خورشيد تقريباً مستقيم است؛ لذا استفاده از گنبد با خيز طاق و ارتفاع زياد و سطح تماس كم با توجه به شرايط اقليمي يزد در آب ­انبارها عملكرد حرارتي مناسب ­تري داشته است.

Due to the dryness of the weather in most parts of Iran and the lack of sufficient rainfall in more than six months of the year in most places, resulting in the seasonality of rivers and the lack of access to water, various arrangements for fresh water supply in the dry seasons has been established. The construction of the AB ANBAR (water reservoir and cistern) is one of innovative ways to supply drinking water. In this regard, AB ANBAR, as its name implies, is to store water in watery seasons and use it during the rest of the year. The main structure of the AB ANBAR consists of an underground storage tank and dome to cover it on the ground. In some areas in Iran a wind catcher has been added to this structure to keep water cool in summer.The construction material used for Ab Anbars were special mortar called Sarooj which was made of sand, clay, lime, goat hair, egg whites and ash in specific proportions, depending on location and climate of the city. Some Ab Anbars had storage space tanks that were rectangular and some of them had cylindrical shape. In order to study the thermal energy potential in the Ab Anbars of Yazd city and the amount of radiation and shading received on the surface of each dome, using the Energy Plus simulation software, thermal analysis was carried out to determine the effect of the dome form on the amount of received sunlight and shadow On the surface of the Ab Anbar dome. The calculations were carried out by selecting several samples of Yazd valued Ab Anbars, based on the form diversity and the type of dome arch. In order to simulate the domes, they were first modeled in Revit software 2017, and then models were transferred to Rhino 5 software, using the honeybee & lady bug, and with the Energy plus Engine analysis of the received solar radiation and shading were done. The amount of received sunlight on the surfaces of the Ab Anbars dome in Yazd is different, and the shape of the dome has a strong relationship with the amount of received radiation. The amount of solar radiation received in the HAJ NASIR dome with an area of 75 square meters is 102906 kW / m2. This amount of solar radiation on the surface of SAHRAIE DASTI dome with an area of ​​137 square meters is 198697 kW / m2 and Get more radiation than HAJ NASIR dome. Another dome sample is BARSOIEH in TAFT with an area of ​​317 square meters is the largest dome among the studied cases. The dome receives 523597 kW / m 2 radiation. The Yazd HAJ GHAZI dome is 133 square meters and receive 215,712 kW / m2. The last one is Dome of SHAH VALLI in Taft, with a total area of ​​194 square meters which absorbs 286,159 kW / m2 radiation. The results of these analyzes shows that the highest amount of solar radiation received from the dome of the studied water reservoirs is BARSOIEH in TAFT dome with the amount of 76046 KW / m2, and the lowest amount of radiation received by Sun is in HAJ NASIR reservoir dome with the amount 102906 kW / m. According to these results, HAJ NASIR dome is the most suitable dome in the hot and dry climate of Yazd and, in heat absorption in shadow area of domes, the largest shading is in dome of BARSOIEH in TAFT. But the point that should be considered in the analyzes is the area of ​​the dome of the Ab Anbars in the Yazd climate, which is, of course, as far as the area of ​​the domes is high, the amount of absorption and shadow of the sun will be greater. For this reason, in the analyzes, uniformity of the dimensions of the Ab Anbars domes were used, so that the optimum dome can be obtained in terms of receiving solar radiation and absorbing heat in the shadowed area. To equalize the domes, the absorption of the sun's radiation of each dome is divided by the amount of shadowing of the same dome, the number obtained indicates the relationship between the amount of radiation and shadow on the dome. That is, greater number shows greater amount of radiation absorbed in that dome comparing shadow casted by the dome. The results show 6 for SAHRAIE DASTI dome, 7 for BARSOIEH in TAFT, 8 for HAJ GHAZI, 11 for HAJ NASIR, and finally the highest number were 12 for SHAH VALLI in Taft. This results shows that the lowest radiation intake is in SAHRAIE DASTI dome and the highest radiation is in SHAH VALLI in Taft, it can be concluded that the most optimal AB ANBAR dome for the Yazd city climate is the dome of SAHRAIE DASTI.