A suitable climatic environment in a greenhouse is particularly important for the growth of crops, and environmental regulation and control are the top priorities for crop production in smart greenhouses. In summer, the temperature in the greenhouse is too high and the crops cannot grow. One of the main factors affecting the indoor environment of the greenhouse is ventilation. The ventilation in the greenhouse allows the exchange of materials and energy between the interior of the greenhouse and the environment, thereby effectively controlling the greenhouse The temperature, humidity, and CO2 concentration of the greenhouse can reach the best condition for the growth of crops in the greenhouse. Therefore, it is very necessary for the research of greenhouse ventilation. Greenhouse exhaust fan blower has become a common ventilation device in greenhouses now.
Greenhouse cooling methods commonly used in greenhouses generally include ventilation cooling, evaporative cooling, wet curtain fan cooling, centralized atomization cooling, and Greenhouse exhaust fan blower. Ventilation cooling includes natural ventilation cooling and mechanical ventilation cooling. Natural ventilation is the use of heat pressure or wind pressure generated inside and outside the greenhouse to make the air inside and outside the greenhouse flow and dissipate heat. Mechanical ventilation is different. It can be divided into three ventilation cooling methods: positive pressure ventilation, negative pressure ventilation, and combined ventilation. Positive pressure ventilation is the use of installed fans for forced ventilation to force outdoor air into the greenhouse, so that the indoor pressure is higher than the outdoor pressure, forming a pressure difference and forcing the indoor air to be discharged. Negative pressure ventilation means that the installed fan is used to exhaust air, so that the pressure in the room is lower than that of the outdoor, and the negative pressure formed will suck the fresh outdoor air into the room. The Greenhouse exhaust fan blower cooling system uses negative pressure ventilation to cool down. At the same time, the use of a fan to discharge high-temperature air and supply fresh cold air is called an intake and exhaust ventilation system, that is, combined ventilation. This kind of ventilation and cooling method is too high in input cost, except for special requirements, and generally has low applicability. Evaporative cooling is the use of the characteristics of water evaporation that need to absorb latent heat. Through the evaporation of water in the air, the latent heat of evaporation is absorbed from the air, so that the air temperature is reduced. The evaporation cooling uses the contact between the water surface and the air to absorb heat, and the liquid surface evaporates. It changes from liquid water to gaseous water, and absorbs a large amount of air sensible heat, so as to achieve the cooling effect of air. The wet curtain-fan cooling system uses a fan for negative pressure ventilation and cooling, and at the same time installs a wet pad at the air inlet, and uses the principle of water evaporation to absorb heat for cooling.
1. The increase in the length of the greenhouse leads to a significant reduction in the wind speed of the curtain, which causes the overall indoor airflow to become slow, thereby slowing down the cooling rate in the greenhouse, intensifying the transpiration of crops, and affecting the normal growth and development of crops.
2. The length of the greenhouse is the same, and the height of the wet curtain is increased to 2.0m, which will expand the cooling area inside the greenhouse and provide a suitable growth environment for crops with higher canopy height.
3. Without changing the power of the greenhouse exhaust fan blower, only increasing the wet curtain area of the greenhouse can ensure that the greenhouse within the length of 48m can achieve a better cooling effect, while the cooling of the greenhouse longer than 64m is restricted to a certain extent. It is especially suitable for the typical climatic environment of high temperature and high humidity. You can consider increasing the number of fans or increasing the power of the fans to increase the exhaust rate and curtain wind speed. Considering various factors, in the construction of Velo glass greenhouse, it is recommended to It is reasonable to configure a wet curtain with a height of 1.5m for a greenhouse of 32m, and a wet curtain with a height of 2.0m for a greenhouse with a length of 48m.