greenhouse ventilation

The greenhouse is ventilated under the simultaneous action of heat pressure and wind pressure. ordinary feelings
, the effect of thermal pressure changes little, and the effect of wind pressure changes greatly. Natural ventilation is a simple and economical ventilation method. Natural ventilation of the greenhouse is achieved through side windows, skylights or vents where the greenhouse covering film is rolled up. The ventilation volume of natural ventilation is related to many factors, such as indoor and outdoor temperature difference, outdoor wind speed and the area, form and position of wind doors and windows. The design ventilation volume of the ventilation system refers to the ventilation capacity used in the design of the ventilation system, that is, the air volume that the system is expected to achieve during operation. The design ventilation volume of the greenhouse natural ventilation system depends on the layout and layout of the greenhouse ventilation windows and vents.

(1) Ventilation openings of sufficient area should be provided so that the designed ventilation volume of the ventilation system meets the maximum necessary ventilation volume requirements.
According to the structural characteristics of the greenhouse, the vent area can be increased as much as possible. (2) Natural ventilation systems generally use openable and closable skylights and side windows. For natural ventilation in a multi-span greenhouse, it is advisable to adopt the method of air inlet through the side walls and air outflow from the top. It is advisable to open ventilation windows on both sides of the roof or open the entire roof. For solar greenhouse ventilation in winter, air vents should be installed on the top of the roof. During spring, summer and autumn ventilation, air inlets should be installed at the lower part of the front roof or the entire front roof should be ventilated. When ridge windows and side wall windows are installed in multi-span greenhouses for ventilation, the area of ​​the ridge window should be the same as the side wall window. The wall and window areas are equal, at least 15% to 20% of the floor area.
(3) In order to effectively utilize the natural ventilation caused by heat pressure and wind pressure, the center height of skylights and side windows should be increased as much as possible, and the heat press air inlet should be placed on the windward side, and the air outlet should be placed on the leeward side to obtain the maximum natural ventilation
The ventilation inlet should be set in the upwind direction of the outdoor wind, otherwise the area of the outlet should be increased to obtain the same air volume. In winter, the air intake for ventilation should be set in the downwind of the outdoor wind. 4) The skylight exhaust direction should be located in the downwind of the local dominant wind direction to avoid wind backpouring from the skylight. For multi-storey greenhouses, the wind entering from the side wall should be avoided as much as possible from the roof window across the side wall
(5) The inlet and outlet should be set respectively in the two areas of the opposite wind pressure on the surface of the greenhouse envelope. The relative design of inlet and outlet is conducive to increasing air flow. The airflow direction will change when the tuyere is adjacent, and the layout should be reasonable
The location of the air outlet.

(6) The direction of outdoor air flow will be affected by the terrain of the greenhouse, green belt, and surrounding buildings, and these factors can be used to change the direction of outdoor air flow in natural problems. Avoid buildings (or structures) and obstacles in front of the air inlet.
(7) The tuyere should be installed with a insect-proof net, and the influence of the airflow resistance of the insect-proof net should be considered, and the airflow resistance will increase after the insect-proof captures insects or accumulates dust.