Room with a Balcony Air Conditioning

Description

This project studies solar-driven heat transfer and natural convection inside a room-and-balcony configuration using ANSYS Fluent. The balcony has a glass roof and one glass wall, and as sunlight radiates into both spaces, buoyancy-driven natural convection becomes the dominant mechanism circulating air within them, since no fans or external forcing are present to drive the flow. The geometry, comprising the room and balcony together, is built in 3D in Design Modeler and meshed in ANSYS Meshing with a structured grid of 290,250 elements.

Methodology

Natural convection here arises purely from buoyancy: as sunlight warms parts of the air, that air loses density and rises, drawing in cooler, denser air to replace it, and this exchange repeats to form a self-sustaining rotating flow. Turbulence is resolved with the standard k-epsilon model, while the P1 solar ray tracing model simulates incoming sunlight and calculates the radiative heat transfer it produces inside the room. The energy equation is active to compute the resulting temperature field, and density is allowed to follow the ideal gas law so that thermally driven buoyancy is captured directly rather than assumed. Ambient air is set at 310 K with a heat transfer coefficient of 20 W/m²K, the room's walls are treated as opaque absorbers of solar radiation, and the glass walls and roof are modeled as semi-transparent, letting solar rays partially pass through into the interior.

Analysis

The results include 2D and 3D contours of velocity, temperature, and pressure, along with streamlines through both spaces. The pressure fields show clear stratification characteristic of natural convection in an enclosed volume, and notably, the pressure distribution in the room runs opposite in direction to that in the balcony, a difference traced to the glass roof: air near that glass boundary tends to stay warmer, which impedes the usual replacement of cool air by hot air and causes air to accumulate lower in the balcony than the convection pattern would otherwise predict. Temperature contours confirm the room reaches noticeably higher temperatures than the balcony, consistent with the room's opaque walls absorbing far more solar heat than the balcony's semi-transparent glass. The streamlines make the underlying convective rotation visible in both spaces, tracing directly how buoyancy-driven circulation moves air through the room and balcony.