Reasonable design of fresh air system is helpful to maximize the effect of fresh air system. Today, I'd like to talk about the main points of fresh air system design for your reference.
The distance between air supply outlet and exhaust outlet should be appropriate
The distance between the exhaust outlet and the air supply outlet shall be at least 3 meters to prevent short circuit of air flow.
Select appropriate air valve
In principle, the error of system air pressure balance is within 10% ~ 15%, so it is not necessary to set the regulating valve, but in fact, it is very difficult to adjust the air pressure only by the size of the regulating pipe, so it is necessary to set the air volume regulating valve for adjustment.
(1) Air volume regulating valve shall be set at the branch of air duct. The three-way regulating valve can be set at the three-way branch, or the regulating valve can be set at the branch.
(2) In order to reduce the loss of resistance, no regulating valve can be set in the obviously unfavorable loop.
(3) The fire control valve can be used to replace the control valve where the fire damper is needed.
(4) The louver air outlet at the air supply outlet should use the air supply outlet with regulating valve, the double louver air outlet with low requirements can be used, and the air volume can be adjusted by adjusting the angle of the air outlet.
(5) The fresh air inlet should be equipped with air valve which can be closed tightly. The thermal insulation air valve should be installed in severe cold area. When there is automatic control, the electric air valve should be used.
Principle of air duct layout
(1) Local resistance should be reduced as far as possible, that is, the number of bends, tees and reducing pipes should be reduced.
(2) The central curvature radius of the elbow should not be less than the diameter or side length of the air duct. Generally, 1.25 times of the diameter or side length can be used.
(3) In order to facilitate the adjustment of the air duct system, the pressure tap should be reserved before and after the branch point of the main pipe. The distance between the pressure tap and the front local pipe fittings should be greater than 5D (D is the diameter of the long side of the rectangular duct or the circular duct), and the distance from the back local pipe fittings should be no less than 2D. The pressure tap should be reserved on the pipe section with stable air flow at the fan outlet.
Determination of fresh air inlet position
(1) The air inlet should be set at the place with clean outdoor air to ensure the air quality.
(2) It should be set on the north wall, avoid the roof and west wall, and should be set in the back of the building, so that the temperature of the outdoor air inhaled in summer can be lower.
(3) The distance between the bottom of the air inlet and the outdoor ground should not be less than two meters. When the air inlet is arranged in the green belt, it should not be less than one meter. It should be arranged on the windward side of the air outlet as far as possible and lower than the air outlet, and the distance should not be less than 10 meters.
New air outlet requires a method
(1) Fixed shutters should be used.
(2) Waterproof shutters should be used in rainy areas to prevent rainwater from entering.
(3) In order to prevent birds from entering, metal mesh should be set in the shutter.
The selection of tuyere shall be in accordance with the requirements
(1) The fresh air outlet and the air supply outlet are double blinded.
(2) The return air port is a grille.
(3) Double blinds are used for air outlet.
(4) As the air volume of fluorine system is generally small, if heating in winter is required, double blinds should be used instead of diffusers.
(5) When the fan coil unit is equipped with two air outlets, the double-layer shutter with regulating valve should be selected.
Air pressure state of the room
(1) The air-conditioned room in the building should maintain positive pressure.
(2) Negative pressure shall be maintained in toilets, washrooms and rooms for various equipment in buildings.
(3) Positive pressure should be maintained in hotel rooms and negative pressure in toilets.
(4) The front hall of the restaurant should maintain positive pressure, and the kitchen should maintain negative pressure. The air pressure in the dining room should be between the front hall and the kitchen.
Layout of air duct in ceiling and design of air supply duct
From top to bottom: smoke exhaust duct, exhaust duct, supply duct, water pipe. Try not to reverse the air in the supply duct to ensure good air flow and air out effect.