The Study on ventilation performance of solar chimney and optimal dimensions

Abstract
All over the world, the growing trend in depletion of energy resource and fuel costs make a large scale-effort to reduce energy consumption; Moreover, a major portion of energy use, about 40% belongs to building sector in heating, cooling and ventilation. Designed various methodologies to reduce total energy use in buildings can help to implement energy-efficiency conservation programme to gain the highest saving results in construction part. Air ventilation is necessary for removing or depleting pollution. This ventilation can be supplied through solar chimney as a passive strategy. Solar chimney works as a simple and practical idea to enhance natural ventilation in adjacent space. Heat transfering in solar chimney is through convection and the driving force is buoyancy force. The solar energy absorbed by chimney causes the air larger between two parallel planes of chimney to be heated so that the air of space in which the chimney entrance is located is sucked in. Therefore, the breeze inside the space lets the fresh air enter the space through window. Solar chimney is employed in vertical or angled position. But the commonest design of solar chimney for ventilation is in vertical form. Applications of solar chimney have attracted many researchers to the issue to discover the most influential parameters. Many researchers have analysed the application of solar chimneys in different configuration, in natural ventilation improvement. The following paper intends to study on impact of applying solar chimney in air ventilation of adjacent compartments in hot and dry climate on Isfahan. Since solar chimney is not a common element in building design, there is no access to a practical model to study on, so computer simulation method is selected as an alternative method to reach on. The final result is concluded from the simulation models of various solar chimney applied to an office building through energy plus software ver. 5 was used for simulation which is an independent simulation engine used to model energy values without any graphic medium so the models are simulated in Ecotect software as graphic medium and then the model geometry is transferred to energy plus software to be calculated. Different models compared together based on different solar chimney by different dimensions. Data recorded included air flow rate and air outlet temperature. The results show the optimum width by the relationship H/11 where H is the chimney height (2m width for 22m height of solar chimney). Two design configurations were considered: the first is a tall solar chimney attached to each floor and the second, solar chimney is attached to only one floor witch air flow rate in second model is more than the first one. Furthermore, the other models with a number of different floors were compared while the area of the solar chimney with optimal dimension spaces (on each floor and with a number of different distance from top of solar chimney) providing required air change is expressed. The maximum air changes occur in seventh floor which is in minimum distance from solar chimney air outlet.