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- Type of Document: Ph.D. Dissertation
- Language: Farsi
- Document No: 40171 (08)
- University: Sharif University of Technology
- Department: Mechanical Engineering
- Advisor(s): Bahadori Nezhad, Mehdi
- Abstract:
- Domed roofs were commonly used in buildings with large areas. These roofs played an important role in the Iranian architecture and had a great effect on the buildings cooling loads. Solar energy absorption causes the roof temperature to increase in comparison with its ambient atmosphere. Wind flow removes some of the heat from the roof, and the rest goes thorough the roof and enters the building.The eometrical configuration of these domed roofs causes the wind velocity to increase over them, resulting in an increase in the convection heat transfer coefficient. Also, the heat transfer of the roof is accentuated by the fact that the area of a domed configuration is considerably greater than a flat one. Passive cooling can be achieved by inserting a hole on top of the dome. In the presence of the hole, the negative pressure over it makes an air flow emanating from the building’s openings toward it. This air flow decreases the inside roof temperature, resulting in a lower radiation heat transfer. The objective of this research was to determine the thermal performance of domed roofs. A 1/10 model of the dome of a theological school in Yazd, Iran, was constructed and tested in a boundary-layer wind tunnel. The model had 12 openings in the wall supporting the dome, and a hole in its apex. These openings represented windows in the actual dome construction. Wind pressure coefficients were measured for the cases when all windows and the hole on top are open or closed, and when the model is turned in a way that the surface between two adjacent windows is facing the wind. Solar radiation received and absorbed by the dome was estimated, and heat transferred to the inside air was determined, employing thermal- and flow networks. A building with flat roof, but with the same dimensions as the dome construction, was considered for comparison. For the dome under consideration, it was assumed to be covered with ordinary material and with glazed tiles. The results of the study showed that domed roof under investigation performed better than the building with flat roof, particularly when the dome was covered with glazed tiles. The result of this study showed the importance of employing dome constructions to cover large areas in mosques, churches, etc. and covering them with glazed tiles. In addition to their aesthetic values, the domes covered with glazed tiles had thermal benefits of keeping the inside air of these buildings relatively cool during the summer months
- Keywords:
- Solar Radiation ; Air Pressure Distribution ; Thermal Performance ; Domed Roofs
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