Use of CFD in Modern HVAC Simulation
Complex HVAC systems consisting of convectors, air grilles and other climate control systems are difficult to evaluate on their performance throughout entire rooms and buildings. CFD simulations offer insight into the strengths and weaknesses of the HVAC system by analysing the thermal comfort at each location in a room.
On request of clients, we assessed the thermal comfort for various HVAC systems in both summer and winter conditions by evaluating typical comfort parameters such as
- draught rate (DR)
- PMV/PPD
- Temperature and operational temperature
- Air flow velocity
- air residence time (also known as age of air)
- and more.
How we simulated it
We used a steady state RANS CFD simulation with the SST k-ω turbulence model to capture the short-duration airflow and mixing effects. In addition the energy transport equation and radiation model (discrete ordinates method) are implemented.
The setup includes:
- Detailed modelling of the HVAC systems
- Effects of internal heat production (e.g. people, lighting and devices)
- Infiltration at the windows
- External head loads (e.g. solar radiation and environmental temperatures)
In this case the HVAC consists of multiple air supply grilles, convectors adjacent to windows and a climate control ceiling. The HVAC system is tested for a winter scenario where the external environment is at -8 °C. Results of the operational temperature show
- Optimal working of the climate control ceiling above the tribunes
- Good levels of temperature regulated by air supply grilles throughout the central oval.
- Cold air infiltration at the windows, based on which the client adjusted the convectors to minimize the effects.
In the second case, we simulated an apartment door swinging open while a person walks in or out. The apartment was assumed to be well ventilated, while the corridor was not. Here, the door motion itself creates strong vortices, leading to much greater mixing than in the lift case.
Air exchanged
- Person entering apartment: 1.14 kg of air
- Person leaving apartment: 1.28 kg of air (slide to see the animation)
Why this matters
These results show that door operation and occupant movement can contribute meaningfully to passive ventilation and contaminant transport, especially in shared indoor spaces such as:
- apartment corridors
- lift lobbies
- offices
- healthcare facilities
- public buildings
CFD can help quantify these effects and support better decisions in ventilation design, infection risk assessment, and building performance studies.