The ventilation system of the veined glass greenhouse is divided into two types: winter closed greenhouse use and summer and spring ventilation. Therefore, the design and configuration are very different.
一. Reasons for the design of winter ventilation system
In cold seasons, greenhouses are often in a tightly closed state. The indoor air does not flow, the relative humidity is high, and it is easy to condense on the leaves, which will cause harm to crops. In order to make the air in the greenhouse flow, reduce the humidity of the leaves, make the indoor temperature and humidity evenly distributed, and eliminate the indoor cold spots, hot spots and high humidity points in the dense leaf area, an air circulation system needs to be added.
二. Parameters of winter ventilation design
Air supply belt air supply
The first is to hang a plastic air supply tube at the bottom along the greenhouse gutter, and there are uniform air outlets around the plastic air supply tube. A positive pressure fan is installed at the end of the air tube to supply air to the shed.
The second is to use multiple low-power circulation fans with a power of about several hundred watts, which are hung on the greenhouse skeleton structure. Several rows can be installed in the direction of the greenhouse span, and the air is relayed above the crop layer to achieve air circulation.
The fan should be hung vertically on the ground, at least 0.6~0.9m above the crop. The fan spacing should not be greater than 30 times the diameter of its impeller. The distance between the last fan and the end wall is about 4.5^-6.0m. The selection of fan flow should make the total flow meet the air flow of 10 L/s per square meter of ground
三. Reasons for natural ventilation design in summer
Natural ventilation is a process of indoor and outdoor ventilation generated by natural wind pressure or air gravity and maintaining a certain pressure difference. It relies heavily on the transpiration of crops to reduce the air temperature and keep it at a level acceptable to crops. Natural ventilation basically does not consume energy and is the most economical ventilation method. When possible, it should be used first.
四. Parameters for summer ventilation design
1. The side window area is usually half of the side wall area.
2. The skylight area should not be less than 15%~20% of the greenhouse ground area. Sometimes half of the roof can be used for windows. Increasing the height difference between the skylight and the side windows is conducive to improving ventilation conditions. The best location for the skylight is at the highest point of the roof.