This informal CPD article Simulation for Indoor Air Quality was provided by SimScale, A new, cloud-based approach to CAE, FEA and CFD.
Simulation for Indoor Air Quality
The built environment sector has been impacted heavily in recent years, in particular, the topic of adequate ventilation and indoor air quality (IAQ) has become prominent. Schools, restaurants, offices, and other types of buildings are working hard to adapt to the changing guidelines and regulations to reassure occupant and public safety. Ventilation is an integral factor in contaminant management strategies as well as occupant thermal comfort and air quality. Here we cover how CFD plays a vital role in accurately simulating airflow, helping HVAC engineers and building designers improve the indoor air quality without compromising on energy efficiency.
CFD Simulation for Ventilation Studies
The features offered by simulation software can be used to virtually test and optimize ventilation strategies. Computational Fluid Dynamics (CFD), the branch of computer-aided engineering that simulates fluid motion using numerical approaches enables engineers to study the flow of air and better understand the environmental and physical properties of ventilation in a room or building.
Various ventilation strategies can be tested simply by changing the location or type of diffuser, heating, or air conditioning units. Similarly, designs can be tested with windows open, windows closed, or any interim opening configuration. Comparative studies allow designers to evaluate each scenario and converge on the best design choices for achieving optimal indoor air quality. Cloud-native simulation platforms facilitate access to this kind of high-performance computing power and high-fidelity simulation from a simple web browser.
Contaminant dispersion is a critical aspect affecting indoor air quality and a preeminent topic on the minds of not only HVAC designers but building services engineers and building managers, alike. CFD studies are a powerful tool to test and validate the effectiveness of a contaminant management system.
Indoor air quality is dependent on several factors. In addition to the source of contaminants, other factors that contribute to IAQ that can be simulated in CFD include:
- The CO2 from occupants - this varies with occupant activity levels and is a pollutant that must be removed constantly and maintained within acceptable levels.
- The rate of air changes per hour in a space (ventilation and infiltration) - mechanical ventilation can be easily controlled. Natural ventilation through purpose-designed openings must be carefully designed and installed. Infiltration, the adventitious leakage of air from a building must be accounted for. All three types of ventilation can be simulated in a CFD model.
- The temperature distribution in the space-convective (buoyancy) drive flows especially can be dominant inside buildings and are difficult to predict. CFD is used to accurately determine the path that air takes throughout a building.
- The building envelope - heat conduction and radiative gains through the building fabric will alter the energy balance and affect indoor thermal comfort. This will, in turn, impact the flow of air.
CFD simulation is useful for determining which parameters listed above will have the largest impact in relation to achieving proper air quality and effective contaminant disbursement. Outputs that engineers can expect from a CFD study include:
- Whole room ventilation rates (Air changes per hour, the mean age of air, etc)
- Fresh air and fresh air ratio
- Placement of air supply and exhaust grills
- The air velocities and air mixing in close proximity to the occupants
With CFD, engineers can establish the optimal conditions for their ventilation strategy design in a virtual environment, before the project reaches a construction or renovation phase. Simulation not only achieves accurate results and security for occupants but reduces both cost and time in the design process.
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