In most parts of China, the summer climate is hot, the outdoor temperature is above 30 ° C, due to the greenhouse effect, the internal temperature of the greenhouse is easily more than 40 ° C, therefore, cooling measures must be taken to ensure that the greenhouse can carry out normal production. As far as it is concerned, this greenhouse effect phenomenon is more obvious, and therefore promotes the development of ventilation equipment, ventilation cooling equipment includes a wide range of aspects: for ventilation, cooling and ventilation cooling together to solve the machine equipment. Ventilation and cooling equipment include: air conditioning, automobile air conditioning, fan, fan, centrifugal fan, negative pressure fan, water curtain and so on. Ventilation and cooling equipment appears as a phrase in the company name, and the main products of this type of company are negative pressure ventilation fans and water curtains. Negative pressure ventilator belongs to the category of negative pressure fan, is the high-end product of negative pressure fan, with better pumping effect, less noise and lower energy consumption. Water curtain is also called wet curtain, used for ventilation and cooling of industrial plants, ventilation and cooling overall solution. Ventilation and cooling equipment is the latest efficient ventilation and cooling method, from Taiwan into China, the earliest ventilation and cooling equipment Co., Ltd. appeared in 2003, the first appeared in Shenzhen and the Pearl River Delta, from the Pearl River Delta to Jiangsu, Yangtze River Delta, Fujian and other regions sales and dissemination.
At present, the commonly used cooling methods in the greenhouse are: ventilation cooling, shading cooling, wet curtain - fan cooling, micro fog cooling, roof spraying cooling, roof spraying white and so on. Ventilation cooling can be divided into natural ventilation cooling and forced ventilation cooling, shading cooling can be divided into internal shading cooling and external shading cooling.
Ventilation and cooling In the design and use of greenhouses, ventilation and cooling are always inseparable.
Generally speaking, greenhouse ventilation has three main purposes:
1, eliminate the waste heat in the greenhouse, reduce the temperature;
2, eliminate excess water, reduce humidity;
3, adjust the gas composition in the indoor air, eliminate harmful gases, and increase the CO2 content in the air. For summer, the main purpose of ventilation is to cool the room, requiring sufficient ventilation volume; For winter, the main purpose of ventilation is to adjust the indoor air composition, in order to heat preservation and energy saving, rely on cold air infiltration ventilation, maintain the minimum ventilation volume to meet the ventilation requirements.
Natural ventilation Natural ventilation is generally set on the top of the greenhouse or the side wall of the window, relying on hot pressure or wind pressure for ventilation, and can be adjusted by adjusting the amplitude of the window to adjust the ventilation.
The main factors that determine the size of natural ventilation are generally: indoor and outdoor temperature difference, greenhouse vent height difference, vent area, vent resistance, outdoor wind speed and direction. The temperature difference between indoor and outdoor, outdoor wind speed and direction are generally uncontrollable factors, so the evaluation of natural ventilation performance of the greenhouse mainly depends on the height difference and the area of the vent.
Whether to use side wall ventilation, or to use roof ventilation, or to use roof and side wall combined ventilation, according to the size and type of greenhouse and the specific local climate environment to decide. Under normal circumstances, the ventilation volume of the roof and the side wall joint ventilation is the largest. But for the greenhouse whose total width is less than 30 meters, the side wall ventilation occupies a large proportion in the whole greenhouse ventilation. For large-area greenhouses, the total area of the general roof vent is much larger than the area of the side wall vent, so the roof ventilation is generally dominant.
The vent should be set in accordance with the air flow law, for the roof vent, should be located at the highest point of the roof as far as possible, in order to form a large height difference. For the side wall vents, they should be located as low as possible, and try to make the side Windows perpendicular to the dominant wind direction from late spring to the Mid-Autumn Festival season.
An important indicator of natural ventilation performance is the value of the actual vent area as a percentage of the greenhouse building area. The higher the ratio, the better the ventilation performance. Therefore, the general opening Angle of the greenhouse window should be as large as possible to increase the actual air intake area.
Natural ventilation is greatly affected by external climate
The cooling effect is not stable, the general indoor temperature is 5~10℃ higher than the outdoor temperature, so the application of ventilation equipment for cooling ventilation is imperative.
The ventilation equipment ventilation is now mainly using negative pressure ventilation fan ventilation box water curtain indoor cooling:
Negative pressure ventilator is a type of negative pressure fan, is a high-end product of negative pressure fan, with better pumping effect, less noise and lower energy consumption. From the material is different from the ordinary negative pressure fan, the use of glass steel shell, die-cast aluminum alloy wind blade, high protection grade aluminum shell motor, anti-corrosion treatment. The difference in design is that the shutter design is in the negative pressure measurement of the fan, improving the shortcomings of the shutter in the positive pressure measurement to increase the exhaust resistance, the air duct resistance is smaller, the air return is smaller, the minimum speed of the product of the belt transmission structure is only 370 RPM, ultra-low noise.
The water curtain is the wet curtain, and the cold fan (environmental protection air conditioning) is the same cooling equipment. The difference between water curtain and environmental protection air conditioning is: environmental protection air conditioning is a combination of wet curtain and traditional fan, water curtain is used with a new and efficient negative pressure fan, environmental protection air conditioning is the wet curtain and fan concentrated in a small box, air supply by the air pipe, belongs to positive pressure ventilation. The water curtain is installed directly on the window to make a wet curtain wall, which is used in negative pressure ventilation.