Sizing static aerators
EOLIOS designs static aerators and natural ventilation systems for industrial sites
- Selecting equipment according to use
- Sizing air inlets to suit site conditions
- Aerator flow calculation
- Study of critical scenarios
- On-site flow measurement
- Improved air distribution and cooling efficiency
- Study of pollution levels
- Location optimization
- Study of associated air treatment systems
Static ventilators allow for the evacuation of gases, fumes, or heat present in a closed system. EOLIOS assists manufacturers in sizing static ventilators.
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Static aerator sizing principle
Define the quantity of air required to operate the workshop:
The first step in sizing static ventilators is to determine the workshop’s ventilation requirements . It is necessary to determine the volume of fresh air needed to replace stale air and maintain acceptable air quality in the workshop.
This air volume depends on the size of the workshop , the number of occupants , the types of pollutants present , and local regulations . It is also essential to define the air exchange rate , that is, the number of times per hour the air must be renewed in the workshop .
Facilitate the elevation of natural air flows:
It’s important to take advantage of the natural air flow in the workshop to facilitate air circulation.
The temperature difference between indoor and outdoor air is a key driver of natural ventilation . To facilitate the upward movement of airflow , it is recommended to create significant temperature variations .
Static aerators should be positioned to take advantage of natural air currents, such as prevailing winds or pressure differences due to temperature variations.
Avoid pollution zones:
Pollution zones , where pollutants are generated or accumulate in greater quantities , must be identified and taken into account when positioning aerators . It is necessary to place aerators near these zones to effectively capture and remove contaminants .
Static ventilators should also be positioned to facilitate the removal of stale air . It is recommended to place ventilators in the highest areas of the workshop to allow hot air and contaminants to escape easily .
Improve ventilation uniformity :
It is important to ensure uniform ventilation throughout the workshop . Static ventilators should be distributed so as to simultaneously cover the workspace , especially dead zones where air does not circulate efficiently .
Avoid obstacles and facilities:
It is essential to consider obstacles and workshop layouts when choosing the location of static ventilators . Obstructions such as machinery, shelving, or equipment can disrupt airflow and reduce the effectiveness of the ventilators .
Comply with fire regulations:
A static ventilator is a passive device used to facilitate smoke evacuation in buildings . Its operation is based on the principle of pressure difference between the inside and outside of the building . By exploiting this pressure difference , the ventilator allows the evacuation of toxic fumes and combustion gases produced during a fire.
It is important to comply with local fire safety regulations . Some regulations may impose specific requirements regarding the size and location of static ventilation units , depending on the type of activity or occupancy of the workshop .
Complying with current regulations and choosing the right static aerators are therefore essential for fire prevention and personal protection.
> As part of smoke ventilation engineering, EOLIOS can assist you in sizing your static ventilators.
How to choose the right size and type of static aerators for natural ventilation?
Choosing a location for static aerators :
The placement of static ventilators is a key factor in ensuring effective ventilation in industrial workshops . The choice of location must take into account several parameters to guarantee optimal air circulation in the workspace.
Define the optimum size :
The size of static aerators is also an important criterion to take into account when sizing.
It’s essential to choose aerators with sufficient airflow to meet the workshop’s ventilation needs.
It is also essential to ensure that the maximum air speed at the aerator outlet remains within its optimum operating range.
Determine the number of aerators:
The placement of static ventilators is a key factor in ensuring effective ventilation in industrial workshops . The choice of location must take into account several parameters to guarantee optimal air circulation in the workspace.
Take into account existing mechanical insufflation or extraction systems:
Before sizing static air vents , it is important to understand the operation of the mechanical supply or exhaust systems already present in the workshop. These systems are generally used to control temperature, humidity, or air quality in an enclosed space or for process purposes . Workshops are often equipped with fans or air extractors to generate airflow in the workspace.
The sizing of static ventilators must be adapted according to the characteristics of the mechanical systems already present in the workshop . It is essential to consider the airflow rates generated by these systems in order to achieve an optimal balance between mechanical and natural airflow . Accurate calculation of the static ventilator sizing will ensure balanced ventilation throughout the workshop .
A thorough analysis of the mechanical systems allows for the optimization of natural ventilation and ensures harmonious collaboration between static ventilators and mechanical systems . By combining the advantages of both methods, it is possible to guarantee efficient and balanced ventilation in the workshop . The expertise of a fluid mechanics specialist is essential for the successful integration of static ventilators with existing mechanical systems .
Size according to existing or future air inlets:
When sizing static ventilators, it is essential to consider the size of the air inlets . Air inlets are responsible for supplying fresh air to an enclosed space , complementing the static ventilators which ensure the removal of stale air.
Consider other factors such as acoustics and ease of maintenance:
In addition to the criteria mentioned above, it is important to consider other factors when sizing static ventilation units. Depending on the site, it is recommended to choose quieter units to avoid disturbing nearby industries.
It is also advisable to choose energy-efficient aerators, thus reducing operating costs. Furthermore, the issue of birds and parasites may arise depending on the industrial activity. Finally, it is preferable to choose aerators that are easy to install and maintain , to facilitate their daily use.
How do you accurately size static aerators?
Which physical principles need to be studied?
The sizing of static air vents is a crucial step in the design of an efficient natural ventilation system . Several factors must be considered, such as the neutral pressure plane , pressure coefficients , and the distribution of static surface pressures . In this chapter, we will analyze these different aspects in detail to provide a better understanding of static air vent sizing.
CFD study of pressure coefficients
Wind exerts a force on static ventilators , which can significantly impact their operation . It is therefore essential to consider these effects when designing these devices .
When the roof is exposed to the wind:
- An overpressure is created on the side exposed to the wind.
- A depression is created on the opposite slope.
Air pressure difference :
- The negative pressure on the opposite side draws air from inside the building.
- An overpressure is created in the volume, proportional to the force of the wind.
- This creates a natural circulation of indoor air.
Overpressure and underpressure zones :
- Over-pressurized zones encourage air ingress.
- Depressed zones encourage air outflow.
Distribution of static surface pressures
- Depressions at the outlets are the driving force behind the building’s natural ventilation.
- The negative pressure in the roof must be high enough to convert all lower vents into air inlets.
What is thermal draft?
Thermal draft is based on the fundamental principle of the density difference between hot and cold air . When a heat source, such as a fireplace or boiler, heats the air inside a confined space, this hot air becomes less dense and naturally rises. Thermal draft is a crucial factor to consider when sizing static ventilation systems, as it directly influences their efficiency .
Thermal draft can be calculated on the basis of several parameters, such as the temperature difference between indoor and outdoor air, the height of the exhaust stack and the configuration of the static aerator.
It is important to note that thermal draft can be influenced by atmospheric conditions, particularly the presence of wind. Wind can alter heat fluxes and create turbulence that can affect the operation of static ventilators. Therefore, this interaction must be considered when sizing ventilators .
Video - Temperature isosurfaces - Steelworks
Analysis and principle of the neutral pressure plane
What is the neutral pressure plane?
The neutral pressure plane is a crucial factor for sizing natural ventilation openings subjected to thermal draft effects. It is an imaginary horizontal plane where the internal pressure is equal to the external atmospheric pressure .
At the neutral plane, air inlets are ineffective because the internal pressure is balanced with the external atmospheric pressure. Conversely, above this plane, the internal pressure is higher than the external pressure , making it an ideal area for air outlets . Below the neutral plane, a low-pressure zone is created, making it a preferred location for air inlets .
Key points to remember about the neutral pressure point :
- In the neutral plane, the air intake and exhaust ports are not very efficient.
- Above the neutral plane, internal pressure is higher than external atmospheric pressure. That is why the air outlet vents should always be located here. Please note that wind effects must be taken into account, as they can occasionally cancel out thermal draft effects.
- Below the neutral plane, a low-pressure zone is created, making this location ideal for air inlets and grilles.
When designing a natural ventilation system :
- The height of the neutral plane must be predetermined.
- The proportion of pressure difference available must be distributed between the air inlet and outlet ports.
- The precise position of the neutral plane and the arrangement of the air inlets can only be verified by an iterative method.
