Understanding how a simple Heater In a Room CFD simulation can predict comfort is a fascinating and practical engineering challenge. When a heater is turned on, it creates invisible currents of warm air that move throughout the space in complex patterns. This process, called natural convection, directly impacts our thermal comfort. Using ANSYS Fluent, we can build a detailed model to predict exactly how heat spreads from a heater to every corner of a room. The simulation captures both buoyancy-driven flow and surface-to-surface (S2S) radiation, which is crucial for accurately modeling how heat moves directly between walls without heating the air in between. This type of building environment simulation helps engineers design more efficient heating systems and optimize indoor climates.

Figure 1:The 3D model used for the Heater in a Room CFD Simulation.

Simulation Process: Modeling the Heater Fluent Simulation

The simulation setup was designed to be clear and efficient, focusing on the heater’s performance. The model consists of two main zones: the solid heater and the surrounding air zone. To ensure high accuracy, a structured grid was applied across the entire model. The heater’s effect was modeled by applying a heat source of 100 W/m³ directly to the heater zone.

A critical part of this Heater Fluent simulation is accounting for all modes of heat transfer. The Surface-to-Surface (S2S) radiation model was activated to calculate the radiative heat exchange between the hot heater surface and the cooler room walls, which is a significant factor in how a room feels.

Figure 2: The structured grid used for the Heater Fluent analysis, ensuring accurate results.

Post-processing: CFD Analysis, How a Heater Creates Room-Scale Airflow

The simulation results provide a clear and fully substantiated story that begins with the heater itself, which is the “cause” of all air movement. The heater, acting as a 100 W/m³ heat source, warms the air immediately around it. As this pocket of air heats up, it becomes less dense and lighter than the surrounding cooler air. This difference in density creates a powerful upward force called buoyancy. This is the invisible engine that drives the entire system. The velocity contour in Figure 3 is the visual proof of this engine in action, showing a distinct thermal plume—a column of fast-moving warm air (red, around 0.124 m/s) rising directly above the heater.

Figure 3: Buoyancy-driven flow due to heater and natural convection in a room

This rising plume of hot air has a direct and predictable “effect” on the entire room’s environment. As the hot air reaches the ceiling, it spreads out, transfers some of its heat to the ceiling, and begins to cool down. As it cools, it becomes denser and heavier, causing it to sink along the cooler outer walls. It then gets pulled back toward the heater at floor level, completing a massive, room-scale circulation loop. The streamlines perfectly illustrate this natural convection loop, revealing the large, swirling patterns that are responsible for mixing the air. This loop directly creates the temperature distribution seen in Figure 4. The result is thermal stratification, where warmer air (orange/yellow, around 301.5K) collects near the ceiling and cooler air (blue) stays near the floor. The most significant achievement of this Heater CFD analysis is the clear demonstration of how a simple, localized heat source (the cause) generates a powerful, self-sustaining natural convection loop (the effect), which in turn governs the complete airflow pattern and temperature distribution that defines the thermal comfort of the entire room.

Figure 4: Temperature field around the heater in the room