THE EFFECT OF WIND-CATCHERS EL-MALAQEF- ON THE INTERNAL NATURAL VENTILATION IN HOT CLIMATES WITH SPECIAL REFERENCE TO EGYPT: A STUDY ON SMALL PHYSICAL MODELS تأثير الملاقف وخصائصها الهندسية على التهوية الطبيعية الداخلية الناشئة عن ضغط الرياح لتتلائم مع المناخ المصرى الحار (دراسة لنموذج مصغر للملقف) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Assiut University Bulletin for Environmental Researches | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Article 1, Volume 10.1, Issue 10.1, March 2007, Page 1-12 PDF (516.1 K) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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DOI: 10.21608/auber.2007.150213 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Abstract | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
ABSTRACT: The research problem has two parts. The first one expresses how to deliver air current (flow movement) due to wind pressure to cover all home parts. The other part expresses how to achieve the thermal comfort in the conditions of Egypt such as high temperatures and low wind speed of the prevailing cold wind. In this work, the effects of the geometrical characteristics of wind catchers on the internal natural ventilation is studied. The aim of this study is to find a way to increase the wind speed from wind catcher all over the internal surrounding spaces. Small physical models is used to derivate the optimum geometrical characteristics of wind catchers that achieve the objective of this research than actual models. Also, the dimensions of the models of wind catchers are analyzed : The effect of the following items on air speed: The mainly second part discusses the controversial effects of the geometrical properties of wind catchers on air speed at wind catcher’s air entries (inlets) and air exits (outlets). These effects are: 1- Different orientations of the entry openings. 2-Different inlet/outlet area ratio. 3-Different numbers and locations of air exits. 4-Cross-areas of the air tunnel and its different forms. 5-The roof angles of wind-catcher. The conclusions of the paper can summarize the conditions under which air speed - at both inlet and outlet openings - increases as follows: When the long axis of the air-entry opening is perpendicularly placed to the wind direction. When the inlet opening area is smaller than the outlet opening area. When the outlet opening is faced inlet opening. When the air tunnel cross-area gets smaller or turns into a circular shape. And when the wind catcher roof angle is between 30º and 55º. يهدف البحث نحو زيادة سرعة الهواء عند فتحات مخارج الهواء للملقف عن طريق استغلال الخصائص الهندسية للملقف مثل توجيه فتحة المدخل طبقاً لاتجاه الرياح والعلاقة العددية والمکانية بين فتحة المدخل وفتحات مخارج الهواء للملقف وفتحات المخارج وعلاقتها بالدور الأرضى أو مساحتها أو مساحة مقطع الملقف، وأخيراً زاوية ميل الملقف ويتم بواسطة تجارب على نموذج مصغر للملقف وجهاز قياس سرعة الهواء ومروحة هوائية. وتوصلنا إلى أن سرعة الهواء تزداد عند فتحات مخارج الهواء فى الحالات التالية: · عند توجيه فتحة المدخل بمحورها الطويل بصورة عمودية على اتجاه الرياح. · عندما تکون فتحات مداخل الهواء أصغر من فتحات مخارج الهواء للملقف. · عندما تواجه فتحات المخارج فتحات مداخل الهواء للملقف. · عندما تقل مساحة فتحة المخرج. · عندما تقل المساحة الداخلية للملقف. · عندما تکون زاوية سقف الملقف حوالى 30°. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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THE EFFECT OF WIND-CATCHERS EL-MALAQEF- ON THE INTERNAL NATURAL VENTILATION IN HOT CLIMATES WITH SPECIAL REFERENCE TO EGYPT: A STUDY ON SMALL PHYSICAL MODELS Ahmed Abdel_Wahab Ahmed Rizk (Ph. D.) Associate Professor, Department of Architecture, Faculty of Engineering, Tanta University E-mail: rizk2003@yahoo.com Mohamed Abd Elmawgoud Abd Elghaffar (Ph. D.) Assistance Professor, Department of Architecture, Faculty of Engineering, Tanta University E-mail: Mawgoud@hotmail.com
EXPERIMENTAL DESIGN:Experiments are carried out using small physical models (15Ï15Ï50) cm, 11Ï11 cm surface area of the inlet opening and finally 11Ï11cm area of the outlet opening. By studying the effect of the geometrical characteristics of wind catcher on air speed at both entry opening and exit openings, it is easy to derive the optimum geometrical chara-cteristics of actual wind catchers that depends on the calculation air speed at both entry. And exit openings. RESULTS AND DISCUSSION: The effect of the geometrical characteristics of wind catcher on air speed of both entry openings and exit openings. 1-Entry Opening’s Orientations (Inlet Orientations): It is found that the effects of different orientations of air entry openings according to wind direction, air speed at outlet openings are as follows:
2-Locations of Outlet Openings to Inlet Openings: Air speed at outlet openings varies according to the location of the outlet with respect to the inlet openings. When the outlet opening faces the inlet opening, air speed increases to a double value of that when the outlet opening located in the same side of the inlet opening as given in table (2), and shown in figure (2). 3-Location of Outlet openings to Ground Level : It is found that the air speed at outlet opening increases when it is near to ground level as given in table (3), and as shown figure (3). 4-The Number of the Outlet Openings: The number of outlet openings-the surface area of each one of them equals 11Ï11 cm- affects air speed at outlet opening. The smaller of the number of outlet openings, the increase of air speed as given in table (4), and as shown in figure (4). 5-The area of the outlet openings: It was observed that the percentage of the wind speed increases by the increase of the area of outlet opening as given in table (5) and shown in figure (5).
6-The cross sectional-area of the air tunnel : It was observed that air speed at outlet openings increases when the cross area of air tunnel decreases as given in table (6), and as shown in figure (6). 7-The Angle of Wind Catcher’s Roof: Studying the different angles of wind catchers’ roof, several values of air speed at exit opening are recorded:
It was found that the effect of the angle of wind catcher’s roof depends on two factors, the location of the outlet opening to the ground level, and the area of the outlet opening.
Table (1): Air speed and orientation of inlet opening
Table (2): Location of inlet/outlet openings and air speed
Table (3): Location of outlet opening to the ground level
Table (4): Number of outlet openings and air speed
Table (5): Air speed and area of outlet openings
Table (6): Air speed at outlet opening/and cross-area of air tunnel
Table (7): Air speed and the angle of wind catcher’s roof
Fig. (2): The effect of location of outlet openings according to face inlet opening
A-The location of the outlet opening: Air speed Increases at outlet openings when the outlet is near to the ground level, when the angle of wind catcher’s roof equals to 30o, air speed at the outlet openings nearly equals the external wind speed. While when the outlet opening is located in the upper part, air speed at the outlet opening decreases to be just 80% of the external wind speed, as given in table (7-a), and as shown in figure (7-a).
B-The area of the outlet opening: Air speed at the outlet opening decreases as the area of outlet decreases, at the half area of outlet opening air speed records only 50 to 60% of external wind speed, as given in table (7-b), and as shown in figure (7-b). The table (7-c) was summarized the three factors; the angle of wind catcher roof, the location of outlet openings and the area of outlet openings.
Table (7-a): The effect of the location of outlet opening according to ground level with the angle of wind catcher roof in the case of complete outlet openings
Table (7-b): Average air speed, area of outlet, and the angle of wind catcher’s roof
Table (7-c): Air speed, outlet location, area of outlet, and the angle of wind catcher’s roof
CONCLUSIONS: From the above study, it can be concluded that the effects of the geometrical characteristics of wind catchers on the air speed at outlet opening, takes the following forms :
RECOMMENDATIONS: Aerodynamic studies should be encouraged to reach the thermal comfort in the indoor environment to reduce the loads on energy used in air conditioning and artificial ventilations. Future studies should be carried out to investigate the performance of real models similar to the models studied in this paper. REFERENCES: 1-Bahadori, M., Viability of Wind Towers in achieving Summer Comfort in the Hot Arid Regions, Brighton, Elservier Science Ltd, 2000. 2-Elmualim, A., Dynamic Modeling of a Windcatcher/Tower for Natural Ventilation, Building Service Engineering, Vol. 27, No. 3, UK, 2006. 3-Elmualim, A., Modeling of Windcatcher for Natural Ventilation, National Renewable Energy Laboratory, Denver, Colorado. USA. 2004. 4-Fathy, H., Natural Energy and Vernacular Architecture, Chicago Press, 1986. 5-Givoni, Man, Climate and Architecture, Elsevier Publishing, 1969. 6-Harris, D., Web, R., Wind Towers' Old Technology to solve a New Problem', 17 th. AIVC, Gothernburg, Sweden,1996. 7-Koenigsberger, Ingersoll, Mayhew, Szokolay, Manual of Tropical Housing and Building, Longman Group Limited, London, 1974.
تأثير الملاقف وخصائصها الهندسية على التهوية الطبيعية الداخلية الناشئة عن ضغط الرياح لتتلائم مع المناخ المصرى الحار (دراسة لنموذج مصغر للملقف) أحمد عبد الوهاب أحمد رزق*، محمد عبد الموجود عبد الغفار** *الأستاذ المساعد، ** مدرس بقسم الهندسة المعمارية - کلية الهندسة - جامعة طنطا
يهدف البحث نحو زيادة سرعة الهواء عند فتحات مخارج الهواء للملقف عن طريق استغلال الخصائص الهندسية للملقف مثل توجيه فتحة المدخل طبقاً لاتجاه الرياح والعلاقة العددية والمکانية بين فتحة المدخل وفتحات مخارج الهواء للملقف وفتحات المخارج وعلاقتها بالدور الأرضى أو مساحتها أو مساحة مقطع الملقف، وأخيراً زاوية ميل الملقف ويتم بواسطة تجارب على نموذج مصغر للملقف وجهاز قياس سرعة الهواء ومروحة هوائية. وتوصلنا إلى أن سرعة الهواء تزداد عند فتحات مخارج الهواء فى الحالات التالية:
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THE EFFECT OF WIND-CATCHERS EL-MALAQEF- ON THE INTERNAL NATURAL VENTILATION IN HOT CLIMATES WITH SPECIAL REFERENCE TO EGYPT: A STUDY ON SMALL PHYSICAL MODELS Ahmed Abdel_Wahab Ahmed Rizk (Ph. D.) Associate Professor, Department of Architecture, Faculty of Engineering, Tanta University E-mail: rizk2003@yahoo.com Mohamed Abd Elmawgoud Abd Elghaffar (Ph. D.) Assistance Professor, Department of Architecture, Faculty of Engineering, Tanta University E-mail: Mawgoud@hotmail.com
EXPERIMENTAL DESIGN:Experiments are carried out using small physical models (15Ï15Ï50) cm, 11Ï11 cm surface area of the inlet opening and finally 11Ï11cm area of the outlet opening. By studying the effect of the geometrical characteristics of wind catcher on air speed at both entry opening and exit openings, it is easy to derive the optimum geometrical chara-cteristics of actual wind catchers that depends on the calculation air speed at both entry. And exit openings. RESULTS AND DISCUSSION: The effect of the geometrical characteristics of wind catcher on air speed of both entry openings and exit openings. 1-Entry Opening’s Orientations (Inlet Orientations): It is found that the effects of different orientations of air entry openings according to wind direction, air speed at outlet openings are as follows:
2-Locations of Outlet Openings to Inlet Openings: Air speed at outlet openings varies according to the location of the outlet with respect to the inlet openings. When the outlet opening faces the inlet opening, air speed increases to a double value of that when the outlet opening located in the same side of the inlet opening as given in table (2), and shown in figure (2). 3-Location of Outlet openings to Ground Level : It is found that the air speed at outlet opening increases when it is near to ground level as given in table (3), and as shown figure (3). 4-The Number of the Outlet Openings: The number of outlet openings-the surface area of each one of them equals 11Ï11 cm- affects air speed at outlet opening. The smaller of the number of outlet openings, the increase of air speed as given in table (4), and as shown in figure (4). 5-The area of the outlet openings: It was observed that the percentage of the wind speed increases by the increase of the area of outlet opening as given in table (5) and shown in figure (5).
6-The cross sectional-area of the air tunnel : It was observed that air speed at outlet openings increases when the cross area of air tunnel decreases as given in table (6), and as shown in figure (6). 7-The Angle of Wind Catcher’s Roof: Studying the different angles of wind catchers’ roof, several values of air speed at exit opening are recorded:
It was found that the effect of the angle of wind catcher’s roof depends on two factors, the location of the outlet opening to the ground level, and the area of the outlet opening.
Table (1): Air speed and orientation of inlet opening
Table (2): Location of inlet/outlet openings and air speed
Table (3): Location of outlet opening to the ground level
Table (4): Number of outlet openings and air speed
Table (5): Air speed and area of outlet openings
Table (6): Air speed at outlet opening/and cross-area of air tunnel
Table (7): Air speed and the angle of wind catcher’s roof
Fig. (2): The effect of location of outlet openings according to face inlet opening
A-The location of the outlet opening: Air speed Increases at outlet openings when the outlet is near to the ground level, when the angle of wind catcher’s roof equals to 30o, air speed at the outlet openings nearly equals the external wind speed. While when the outlet opening is located in the upper part, air speed at the outlet opening decreases to be just 80% of the external wind speed, as given in table (7-a), and as shown in figure (7-a).
B-The area of the outlet opening: Air speed at the outlet opening decreases as the area of outlet decreases, at the half area of outlet opening air speed records only 50 to 60% of external wind speed, as given in table (7-b), and as shown in figure (7-b). The table (7-c) was summarized the three factors; the angle of wind catcher roof, the location of outlet openings and the area of outlet openings.
Table (7-a): The effect of the location of outlet opening according to ground level with the angle of wind catcher roof in the case of complete outlet openings
Table (7-b): Average air speed, area of outlet, and the angle of wind catcher’s roof
Table (7-c): Air speed, outlet location, area of outlet, and the angle of wind catcher’s roof
CONCLUSIONS: From the above study, it can be concluded that the effects of the geometrical characteristics of wind catchers on the air speed at outlet opening, takes the following forms :
RECOMMENDATIONS: Aerodynamic studies should be encouraged to reach the thermal comfort in the indoor environment to reduce the loads on energy used in air conditioning and artificial ventilations. Future studies should be carried out to investigate the performance of real models similar to the models studied in this paper. REFERENCES: 1-Bahadori, M., Viability of Wind Towers in achieving Summer Comfort in the Hot Arid Regions, Brighton, Elservier Science Ltd, 2000. 2-Elmualim, A., Dynamic Modeling of a Windcatcher/Tower for Natural Ventilation, Building Service Engineering, Vol. 27, No. 3, UK, 2006. 3-Elmualim, A., Modeling of Windcatcher for Natural Ventilation, National Renewable Energy Laboratory, Denver, Colorado. USA. 2004. 4-Fathy, H., Natural Energy and Vernacular Architecture, Chicago Press, 1986. 5-Givoni, Man, Climate and Architecture, Elsevier Publishing, 1969. 6-Harris, D., Web, R., Wind Towers' Old Technology to solve a New Problem', 17 th. AIVC, Gothernburg, Sweden,1996. 7-Koenigsberger, Ingersoll, Mayhew, Szokolay, Manual of Tropical Housing and Building, Longman Group Limited, London, 1974.
تأثير الملاقف وخصائصها الهندسية على التهوية الطبيعية الداخلية الناشئة عن ضغط الرياح لتتلائم مع المناخ المصرى الحار (دراسة لنموذج مصغر للملقف) أحمد عبد الوهاب أحمد رزق*، محمد عبد الموجود عبد الغفار** *الأستاذ المساعد، ** مدرس بقسم الهندسة المعمارية - کلية الهندسة - جامعة طنطا
يهدف البحث نحو زيادة سرعة الهواء عند فتحات مخارج الهواء للملقف عن طريق استغلال الخصائص الهندسية للملقف مثل توجيه فتحة المدخل طبقاً لاتجاه الرياح والعلاقة العددية والمکانية بين فتحة المدخل وفتحات مخارج الهواء للملقف وفتحات المخارج وعلاقتها بالدور الأرضى أو مساحتها أو مساحة مقطع الملقف، وأخيراً زاوية ميل الملقف ويتم بواسطة تجارب على نموذج مصغر للملقف وجهاز قياس سرعة الهواء ومروحة هوائية. وتوصلنا إلى أن سرعة الهواء تزداد عند فتحات مخارج الهواء فى الحالات التالية:
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REFERENCES:
1-Bahadori, M., Viability of Wind Towers in achieving Summer Comfort in the Hot Arid Regions, Brighton, Elservier Science Ltd, 2000.
2-Elmualim, A., Dynamic Modeling of a Windcatcher/Tower for Natural Ventilation, Building Service Engineering, Vol. 27, No. 3, UK, 2006.
3-Elmualim, A., Modeling of Windcatcher for Natural Ventilation, National Renewable Energy Laboratory, Denver, Colorado. USA. 2004.
4-Fathy, H., Natural Energy and Vernacular Architecture, Chicago Press, 1986.
5-Givoni, Man, Climate and Architecture, Elsevier Publishing, 1969.
6-Harris, D., Web, R., Wind Towers' Old Technology to solve a New Problem', 17 th. AIVC, Gothernburg, Sweden,1996.
7-Koenigsberger, Ingersoll, Mayhew, Szokolay, Manual of Tropical Housing and Building, Longman Group Limited, London, 1974. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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