Solar Chimney: Buoyancy Force

Solar Chimney: Buoyancy Force — ANSYS Fluent CFD Simulation

Description

This project uses ANSYS Fluent to simulate buoyancy-driven airflow in a solar chimney, a passive ventilation technology central to sustainable building design. A solar chimney works without any mechanical energy: solar energy absorbed at the chimney surface heats the adjacent air, and the resulting buoyancy — the stack effect — drives air up the vertical channel and pulls fresh air through the building. This module focuses on that buoyancy force as the engine of the whole system, examining how heat applied at the chimney surface sets the air in motion and sustains natural ventilation. Within the Renewable Energy: Beginner CFD Training Package, it follows the basic natural-convection chimney case, building toward a fuller treatment of how solar heating governs chimney performance.

Methodology

The setup begins with a meshing strategy that resolves both the large-scale chimney structure and the finer detail of the airflow channel. The energy equation is activated to capture the temperature field, and gravity is included so that the density differences produced by the heating drive the buoyant flow — the core mechanism of the simulation. The solar energy input is represented on the chimney surface to model the heat that sets the air in motion, together with ambient atmospheric conditions and pressure boundaries that reproduce natural ventilation. Turbulence, heat-transfer, and buoyancy models are selected to suit a low-speed, buoyancy-driven flow rather than a forced one. The setup also lends itself to studying how the level of heat input affects performance, by varying the solar intensity and examining the chimney under different operating conditions.

Analysis

Post-processing focuses on the temperature contours, which reveal the thermal stratification and heat distribution within the chimney, and the velocity vector fields, which show how effectively the buoyancy-driven ventilation performs. Linking heat input to performance, the results show how changes in solar intensity influence the airflow rate and temperature distribution, and how the chimney behaves under different operating conditions. From these, ventilation rates and thermal efficiency can be evaluated across configurations, and the insight used to refine key design parameters such as chimney height, width, and inclination angle. By the end of this project, you'll be able to set up a buoyancy-driven solar chimney simulation in ANSYS Fluent, interpret the temperature and velocity fields to assess ventilation performance, and apply those insights to the design of solar chimneys and similar passive systems for sustainable, energy-efficient buildings.