Ventilation method of glass greenhouse

1. Natural ventilation: Most of the time, the glass greenhouse relies on natural ventilation to adjust the indoor environment. The structure of large-scale production glass greenhouses is generally a double-slope multi-span greenhouse, and the ventilation method is to set up ventilation windows on the side walls and roof ridges. The total ventilation area is not less than 15% of the greenhouse area, and it is recommended to be greater than 30%. When the roof ridge window is opened, it is recommended that the window sash can be inclined upward than the horizontal plane. When it is fully opened, it forms an angle of 100 with the horizontal plane to obtain a good ventilation effect. The amount of natural ventilation is related to wind speed, wind direction, position of ventilating window, area of ventilating window, and temperature difference between inside and outside the greenhouse. When the total area of the ventilating windows is 27% of the indoor floor area, if only the ridge is ventilated, even if the outdoor wind speed reaches 10 km/h, the ideal air exchange rate of 0.75 times per minute will not be achieved; when the ridge ventilating windows and side walls When the ventilation windows are fully opened, the air exchange rate can reach 0.68 times/minute under almost no wind, which is close to the normal recommended air exchange rate of 0.75 times/minute.

2. Although the forced ventilation glass greenhouse relies on natural ventilation to adjust the environment most of the time, when the temperature in summer is high, especially when the outdoor temperature exceeds 33℃ in hot weather, it is difficult to meet the cooling requirements of the greenhouse by natural ventilation alone. And cooperating with other measures to cool down is a common method in production. Forced ventilation is the use of fans to convert electrical or other mechanical energy into wind energy, forcing air to flow to ventilate the greenhouse and achieve a cooling effect. The theoretical cooling limit of forced ventilation is that the indoor air temperature is equal to the outdoor air temperature. Because at this time, the temperature difference between inside and outside the greenhouse is zero, and the ventilation is infinite, which is impossible in practical applications. Due to the physiological reasons of mechanical equipment and plants, the ventilation intensity of the general greenhouse is 0.75 air changes per minute to 1. 5 times, the temperature difference between inside and outside the greenhouse can be controlled within 5℃.