n. samkhanian

Ancient wind catchers of Yazd city as net zero energy building components request the detailed numerical and experimental studies to renovate and reuse in old part of the city and for developing the new design strategies in future. In this ingenious natural ventilation strategy no other energy sources are required except wind and sun. In this research, the effect of both wind and sun on the flow and thermal behaviour of the solar-wind catchers of Yazd city - a city with very high solar radiation - in Iran, are investigated numerically and experimentally. This paper represents a systematic evaluation of isothermal 3D CFD modelling for predicting mean air velocity distributions over and through the wind catcher at three reference wind directions of 330°, 90° and 150°, using Open source CFD package (OpenFOAM). The evaluation is based on a grid-sensitivity analysis and on validation with full scaled long term measurement data set. The validated CFD simulation results show that steady RANS with Standard k−ɛ model, in spite of its limitations, can accurately predict the flow behaviour of wind catchers at wind direction of 90° with the average deviations of 19%, which is considered a good agreement against the long term experimental results. Moreover, the thermal behaviour of wind catcher during a summer day is discussed. The study reveals that the solar wind catchers of Yazd city, is quite effective in lowering air temperature and enhancing air circulation through the buildings. The result of this study will be useful for designing solar-wind catchers under hot and dry climate conditions.