بررسي تجربي جريان درون و اطراف يك بادگير دو طرفه با استفاده از تونل باد و تونل دود

چكيده انگليسي :

91 Experimental study of flow inside and outside of a two sided wind catcher by wind tunnel and smoke tunnel Mohammad Afshin m afshin@me iut ac ir Date of Submission 2014 12 27 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Ahmad Sohankar asohankar@cc iut ac irAbstract During recent years considerable attempts have been made to apply the natural ventilation due to theincrease of the human concern about environmental pollution and the need for efficient energy sources Ventilation with the use of renewable energies and without a need for mechanical system is defined as thenatural ventilation such as wind catcher and solar chimney Wind catchers as environmental friendly andsustainable energy systems are traditionally used in the Middle East countries especially in central region ofIran for providing fresh air of buildings Wind catchers also reduce environmental pollution and coolingcosts and they create a favorable and healthy environment for residents compare with mechanicalventilation systems such as air conditioning and chiller Wind catchers are able to catch fresh air with highvelocity and less dust at high altitude and induce it from the windward channels into the building In this study natural ventilation performance of a two sided wind catcher is investigated for different windangles 0 90 and wind speeds 10 20 m sec by experimental wind tunnel and smoke flow visualization To achieve this purpose a 1 50 scale model of a real wind catcher in the city of Yazd central region of Iran is employed The ventilated flow rate and the pressure coefficients around all internal surfaces of a two sided wind catcher are measured in order to find the influences of the wind direction and wind speed on theventilation capacity It is found that the averaged pressure coefficients decrease by increasing the windangle and their maximums occur at a zero wind angle There is a wind angle where the pressure coefficientof the windward opening is equal to that for surrounding This angle is about 55 and is denoted as thewindward transition angle where no airflow passes through the windward opening and only air flowsbetween the window and the leeward opening It is also found that no airflow passes through the window atthe wind angle of 39 window transition angle Flow rate through the windward and leeward channels ofthe wind catcher for different wind angles and wind speeds are calculated based on the velocitymeasurement by hot wire anemometer The results show that the capacity of wind catcher increases withincreasing the external wind speed Wind tunnel experiments and smoke flow visualization show theseparated flow wake region Kelvin Helmholtz KH vortices on the separating shear layer over the wind catcher and the formation of two opposite vortices inside the wind catcher These two vortices aresymmetric and small in size at 0 At higher wind angle they become asymmetric and larger in size Theresults also show that the performance of the wind catcher in the high density urban areas is dependent onthe upstream structure height and its distance from the wind catcher The results show that using the shortupstream object from the wind catcher increases the airflow to the building Employing the upstreamobjects with height greater than half the height of the wind catcher causes the performance of the wind catcher is reduced Keywords Natural Ventilation Two Sided Wind Catcher Wind Tunnel Smoke Tunnel SmokeFlow Visualization

افشين، محمد

بررسي تجربي جريان درون و اطراف يك بادگير دو طرفه با استفاده از تونل باد و تونل دود

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