Investigation of solar chimney to improve thermal residential comfort

Abstract

This thesis presents a comprehensive numerical investigation into the thermal behavior and aerodynamic performance of a roof-integrated inclined solar chimney, designed as a passive natural ventilation and cooling solution to improve residential thermal comfort in hot, arid regions. Focusing on the extreme summer meteorological conditions typical of the Ouargla region in Algeria, a mathematical framework was established by developing detailed one-dimensional steady-state energy balance equations for the key system components: the glass cover, the internal airflow channel, and the blackened absorber plate. To solve the interconnected thermal network, a specialized numerical simulation code was developed in the MATLAB programming environment. The system of governing algebraic energy equations was formulated into a matrix layout and solved using the determinant method to calculate transient component temperatures, mass flow rates, and induced air velocities. The computational model was validated against established experimental and theoretical data from the literature (Mathur et al., 2006). The validation showed high statistical agreement across all monitored variables including glass, absorber, and fluid temperatures confirming the physical soundness and parametric reliability of the developed code. A systematic parametric study was subsequently conducted to evaluate the sensitivity of the system performance to geometric modifications, specifically focusing on chimney tilt angles (30°, 45°, and 60°), internal channel depths (0.1 m to 0.3 m), and inlet/outlet slot heights (0.1 m to 0.3 m) across daily solar radiation cycles. The numerical results demonstrate that while a larger channel depth and slot height (0.3 m × 0.3 m) maximize the absolute mass flow rate (reaching a peak of 142.48 kg/h at an inclination of 60°), the optimum aerodynamic and thermal performance for localized structural cooling is achieved with narrower configurations. The findings yield a definitive architectural engineering design recommendation: for hot, desert environments like Ouargla, an inclined solar chimney with a length of 1 m, a tilt angle of 60°, a channel depth of 0.1 m, and an inlet/outlet slot height of 0.1 m represents the optimal configuration. Under these specific conditions and peak solar irradiance, the system maximizes the buoyancy-driven stack effect, yielding the highest fluid temperature differentials (with fluid temperatures reaching up to 338.21 K) and achieving a maximum induced peak airflow velocity of 0.326 m/s. Ultimately, this research validates the integration of inclined roof solar chimneys as a highly feasible, low-enthalpy cooling strategy capable of significantly decreas-ing building reliance on mechanical air conditioning and minimizing residential energy con-sumption in desert climates.