Façade HVAC with Radiation

Description

This project simulates the airflow through the gap between the two walls of a building's double façade using ANSYS Fluent, under steady-state, pressure-based conditions with gravity included. The 3D geometry, created in Design Modeler, is a rectangular chamber of 3 × 1.5 × 0.2 m fitted with 120 rows of thin shading plates angled at 45 degrees in a shutter-like arrangement. These plates, positioned between the two façade walls, are the key element driving ventilation within the cavity. The model is meshed in ANSYS Meshing with an unstructured grid of 4,264,442 elements. The goal of the study is to characterize the upward airflow and heat transfer that develop in the space between the two shells and around the shading plates.

Methodology

The energy equation is enabled to resolve the temperature distribution, and turbulence is modeled with the standard k-ε model. Atmospheric pressure boundary conditions are applied at both the inlet and outlet of the cavity, allowing buoyancy-driven upward flow to develop naturally from the density variations produced by pressure and temperature changes. Since solar heating of the shading plates is the primary driver of these temperature changes, the Discrete Ordinates (DO) radiation model is used together with the solar ray-tracing model. The surrounding ambient air is taken at 300 K with a heat transfer coefficient of 10 W/m²·K.

Analysis

Post-processing produces 2D and 3D contours of pressure, velocity, and temperature, along with 2D and 3D pathlines. The 2D contours are presented on the XY plane at the mid-section of the cavity between the two façade walls. Velocity 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. The results reveal the upward, buoyancy-driven flow and the heat transfer around the shutter plates within the double-façade cavity.