For greenhouse cooling, cooling pad and exhaust fan are the first choice. We make reasonable selection according to the cooling system of cooling pad and exhaust fan.
The cooling system of cooling pad fan generally adopts negative pressure longitudinal ventilation. In the greenhouse, the distance between the fan and the cooling pad is preferably 30-70m, and the channel resistance is about 25-40Pa. The fan must be selected to meet the ventilation volume required under the static pressure of 25.4Pa. The fan selected for the cooling pads exhaust fan cooling system is a low-pressure large flow axial flow energy-saving fan.
When selecting the cooling pad exhaust fan for greenhouse cooling, customers should pay more attention to the installation, because the reasonable installation, which can significantly improve the cooling effect.
The exhaust fan is generally arranged on the gable at one side of the greenhouse, and cooling pad is usually arranged on the gable at the other side.
In addition to the heat transfer efficiency and resistance characteristics of the cooling pad materials, the wet strength, corrosion resistance, service life, dimensional accuracy and surface quality of the cooling pads blocks must be considered when the selection.
The arrangement of cooling pad and exhaust fan shall be generally in the upwind direction of the greenhouse, and the exhaust fan shall be in the downwind direction of the greenhouse. The air inlet of the cooling pad is not necessarily continuous, but it is required to be evenly distributed. If the air inlet is discontinuous, the air flow velocity shall be above 2.3m/s.
The gap between the cooling pad or the cooling pad wall and the air inlet shall be sealed to prevent the penetration of hot air from affecting the cooling effect of the pads.
The cooling pad water supply needs to be adjusted during use to ensure that there is fine water flowing down the cooling pad ripple, so that the entire cooling pad is evenly wetted, and there is no dry belt or concentrated water flow on the internal and external surfaces that has not been watered.
Keep the water source clean, the pH of the water is between 6 and 9, and the conductivity is less than 1000 μ Ω。 The water tank must be covered and sealed, and the water tank and circulating water system shall be cleaned regularly to ensure that the water supply system is clean. In order to prevent the growth of algae or other microorganisms on the cooling pads surface, 3~5mg/m3 chlorine or bromine can be put into the water during short-term treatment, and lmg/m3 chlorine or bromine can be put into the water during continuous treatment.
When the number of exhaust fans is designed to be multiple, it is recommended to divide all fans into 2 or 3 groups at certain intervals, so as to control the operating at the same time, adjust the ventilation flow according to actual needs, and maintain the air flow in the greenhouse is generally uniform. Louver shall be set outside the fan to prevent air backflow or invasion of pests and dirt during shutdown. The inner side of the fan shall be provided with a protective cover to prevent the human body and the debris bar from touching the parts.
Attention shall be paid to the cooling pad fan system in daily use: shut down the fan 30 minutes after the water pump stops to ensure that the cooling pad is completely dried; After the cooling pad stops running, check whether the water in the water tank is drained to prevent the bottom of the cooling pad from being immersed in water for a long time.
In case of scale or algae formation on the surface of the cooling pad, then shall be dried thoroughly and then brushed up and down with a soft bristle brush, and the water supply system shall be started for washing to avoid washing the cooling pad with steam or high-pressure water.
