Articles
COOLING OF GREENHOUSES WITH COMPRESSED AIR FOGGING NOZZLES
For this purpose, two similar multiarched type.
EVA covered greenhouses were compared, each having a soil surface of 19.2 x 12 mts.
Twenty six nozzles were installed in one of the greenhouses, so each nozzle covered 8.9 sqm. of greenhouse soil.
Compressed air at pressures ranging from 300 to 600 kpa. was mixed inside the nozzles with water at similar pressures forming a dense fog.
Cyclamen persicum was grown in both greenhouses under a shading screen of 45 % transmissivity.
Microclimate measurements included air temperature at different levels, relative humidity, plant tissue temperature. cover temperature, total solar radiation and net radiation.
External data were recorded at a meteorological station located in the vicinity.
Results show that the evaporative cooled greenhouse lowered its temperature 3.0°C on average, compared to the control greenhouse.
Maximum temperature reduction during sunny days was 5.0°C. Humidity was accordingly increased.
For ventilation flows up to 50 air renovations per hour, the cooling system was capable of maintaining a relative humidity of 85% in shaded greenhouses.
To optimize system performance, the relationship between transpiration and environment for the main greenhouse crops needs to be developed, due to the importance of transpiration in the daily energy balance.