Solar chimney for promoting cooling ventilation in southern Algeria

Abstract

In hot climates ventilation can be a useful means of cooling dwellings, if the outside air is cooler than that inside the dwelling. Often, in hot regions the outside air is so hot during the day that cooling by ventilation is of no benefit until the evening when the outside air cools. Ventilation can then be beneficial, and can be promoted by a sun-warmed cavity or 'solar chimney' added to a building on the sunward side. The cavity may be of any material of high thermal capacity. Heat from the sun is stored within the walls and heats the air within. The cavity is closed at the top and bottom by dampers. These, when opened in the evening, allow the buoyant hot air contained within to rise, drawing cooler outside air into the building. This process continues until the stored energy is consumed. The performance of a typical cavity in inducing ventilation into a house is studied experimentally and theoretically. The measurements are made on a full-scale model under steady-state conditions. Cavity width and air inlet area are important parameters in this study. Measurements are made on the temperature and velocity of the air. Observations on air flow patterns in the room and the cavity are made. A dynamic model is developed based on a finite-difference technique, and used to examine the performance of the cavity in various circumstances. The results show that air movement can be produced by a sun-warmed cavity if the dimensions of inlet and cavity width are kept to certain values, and that thermal comfort can be improved.