GREENHOUSE EVAPORATIVE COOLING: MEASUREMENT AND DATA ANALYSIS

Temperature and humidity gradients were investigated during summer in a commercial greenhouse producing cutroses, equipped with a ventilated coolingpad system and a halfshaded plastic roof. In a steady regime, the cooling processreached 80% efficiency and succeeded in maintaining greenhouse temperatures that were cooler (up to 10
C lower) thanoutside. In the unshaded half of the greenhouse, the inlet air temperature increased from the pads to the middle of thegreenhouse, while the humidity content remained constant. In the shaded half of the greenhouse, plant transpirationhumidified the air, but the air temperature increased only moderately. In early morning and late afternoon, the moist and coolair coming from the pads seemed to induce condensation on the soil, especially in the first (unshaded) half of the greenhouse.The physical data were compared with those predicted by an analytical model describing the greenhouse as a heat exchanger.The model helped to understand the particular temperature and humidity profiles of the air flow along the greenhouse. It alsosuggested that greenhouse roof shading could be avoided in dry climates because the evaporative cooling process wassufficient to prevent overheating.