Radiation: Facade Considering Radiation, HVAC

Double Facade Airflow — ANSYS Fluent CFD Simulation

This project simulates airflow through the gap between the two walls of a building's double facade using ANSYS Fluent, under steady-state, pressure-based conditions with gravity effects included.

Geometry and Mesh

The 3-D geometry was created in Design Modeler and consists of a rectangular chamber measuring 3 m × 1.5 m × 0.2 m, fitted with 120 rows of thin shading plates angled at 45 degrees, arranged in a shutter-like configuration. The model was meshed in ANSYS Meshing using an unstructured mesh, totaling 4,264,442 elements.

The ambient air surrounding the shells is assumed to be at 300 K, with a heat transfer coefficient of 10 W/m²·K. The shading plates positioned between the two facade walls play a key role in driving the ventilation process within the cavity.

The aim of the study is to characterize the upward airflow and heat transfer occurring in the space between the two shells and around the shading plates.

Methodology

The energy equation is enabled to capture temperature distribution, with turbulence modeled using the standard k-epsilon model. Pressure boundary conditions equal to atmospheric pressure are applied at both the inlet and outlet of the cavity, allowing buoyancy-driven upward flow to develop naturally from density variations caused by pressure and temperature changes. Since the primary driver of these temperature changes is solar heating of the shading plates, the Discrete Ordinates (DO) radiation model is used together with the solar ray tracing model.

Results

The simulation produces 2-D and 3-D contours of pressure, velocity, and temperature, along with 2-D and 3-D pathlines. The 2-D contours are presented in the XY plane at the mid-section of the cavity between the two facade walls. Velocity distribution is also plotted along a line in the XZ plane at a height of 2 m from the floor, running through the geometric center between x = -0.1 and x = +0.1, consistent with the 45-degree orientation of the shading plates.

Geometry and mesh files, along with a comprehensive training video walking through the full solution process and result extraction, are available as part of this package.