Atrium Natural Ventilation

Description

This project presents a numerical simulation of natural ventilation inside an atrium building, incorporating DTRM radiation heat transfer using ANSYS Fluent. The model represents the interior of a simple atrium structure featuring three-story rooms arranged on two sides of a central atrium space.

Each room includes an airflow inlet at its lower section, with a corresponding exit panel positioned on the opposite wall. Air exiting each story rises through the central atrium and ultimately escapes through an outlet panel located at the building's highest point. Various heat sources — including thermal loads and electrical equipment — are present both within the central atrium and inside each room, while the building's exterior is modeled as glass, directly exposed to solar radiation.

Heat transfer in this model occurs through conduction and convection, with radiation heat transfer also incorporated into the simulation. The goal is to examine how these combined heat transfer mechanisms, along with solar radiation, influence natural ventilation and air conditioning performance within the building.

The 3D geometry was built in Design Modeler, representing the atrium's central volume flanked by two three-story wings, each with its own inlet and outlet per floor. The model was meshed using ANSYS Meshing with an unstructured grid, generating 709,511 cells.

DTRM Methodology

Radiation heat transfer — alongside conduction and convection — describes how all materials at a given temperature emit heat into their surroundings, and becomes especially relevant in cases involving high-temperature sources such as flames.

ANSYS Fluent offers several radiation modeling approaches; this project uses the Discrete Transfer Radiation Model (DTRM), which assumes that radiation leaving a surface element within a defined range of solid angles can be approximated by a single ray.

Solar Ray Tracing is also applied to capture the effect of solar radiation, requiring only the relevant solar input data for the model. The building in this simulation is oriented southwest and located in Montreal, Canada, analyzed at 1:00 PM on July 15 — data that determines the direct and diffuse irradiation levels as well as the direction of the solar rays.

Conclusion

The results yield contours for temperature, pressure, velocity, and density, along with velocity vector fields. These results show that air within each room is heated by the defined floor-level heat sources. The atrium's natural ventilation system then draws this heated air out through each story's exit panel into the central atrium space, where it rises and exits through the building's upper outlet — establishing an effective, self-sustaining airflow circulation throughout the structure.