How to choose the right air diffusers/grilles?

Selection principle:

• The type, function, scope of application and structure of the air diffusers/grilles should be fully understood, and the corresponding air diffusers /grilles type should be selected according to the engineering characteristics, the required air flow organization type, adjustment performance and air supply mode.
• According to the required air volume (supply air, return air or exhaust air), in the neck of the air diffusers/grilles (or the entrance and exit section of the air diffusers/grilles) allowed within the range of wind speed, determine the model size of the required air diffusers/grilles.

• Check the main technical performance of the selected air diffusers/grilles, such as airflow range, total pressure loss, noise index, wind speed and regional temperature difference of the airflow sent to the working area.
• Determine the layout and installation mode of the selected air outlet and the connection mode with the air duct. 

Key points of selection:

• The layout of air diffusers/grilles should comprehensively consider the factors such as indoor air flow organization, noise, aesthetic requirements of building decoration, installation and maintenance, and economy. In the selection, the air diffusers/grilles wind speed should be determined, and the air diffusers/grilles air volume, effective area and range should be calculated. Pay special attention to the impact of construction beams or columns on air flow. For some air conditioning areas with special technical requirements and large air volume occasions, the selection of air diffusers/grilles should be supplemented by computer simulation (CFD) method.
• When the upper part of the air supply, the general room should use the side of the shutter or slit air diffusers/grilles, the side of the air supply should be attached; When there is a suspended ceiling, round and square diffusers should be used according to the air flow requirements of the height of the air conditioning area and the use place. Public buildings with large space or tall factories with room temperature fluctuation range greater than or equal to 1.0 ° C should use spout jet diffuser or swirl air diffuser.

• The installation of side-mounted displacement air supply diffuser should be less than 0.8m from the ground; The exit wind speed should not be greater than 0.2m/s for civil buildings and 0.5m/s for industrial buildings.
• For indoor places with large heat dissipation (such as computer rooms) or tall Spaces (such as theaters), the lower air supply outlet with stable airflow characteristics should be preferred.
  If the building structure is limited, the air diffusers/grilles with good induction performance should be preferred. When sending hot air in winter, attention should be paid to the phenomenon of indoor air thermal stratification, and air supply diffusers/grilles with winter and summer adjustment functions should be selected.
  For places where the installation height of the air supply outlet is greater than 4m, it is appropriate to use the air outlet with adjustable jet direction to adapt to the change of load.
  
• The outlet wind speed of the air supply diffusers/grilles should be determined according to the air supply mode, the type of the air supply outlet, the installation height, the allowable indoor wind speed and noise. When the requirement of noise reduction is high, the air supply of louver air grilles, air diffuser, and slit air grilles should adopt 2-5m /s wind speed, and the air supply of jet nozzle diffuser can adopt 4-10m /s.
• The wind speed near the return air grille decays rapidly, which has little influence on the indoor air flow organization. Three factors should be considered in determining the surface wind speed of the return air grille: First, to avoid excessive wind speed near the return air grille, to prevent the discomfort of people who often stay near the return air outlet; Second, do not raise dust and increase noise due to excessive wind speed; The third is to reduce the section of air diffusers/grilles as much as possible to save the initial investment.
  

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