Experimental Verification of Control Logic for Operation of a Fog Cooling System for a Naturally Ventilated Greenhouse

Abstract

The validity of a developed control logic for operation a fog cooling system was verified in a naturally ventilated greenhouse at durations of fog cooling system operation cycles (tf+s) of 60, 120 and 240 s, then at constant duration of fog cooling system operation (tf) of 35 s. The capabilities of the proposed control logic were evaluated from the viewpoint of changes in dry bulb (or air) temperature (Tdi) and relative humidity (RHi) inside the greenhouse. Even when the tf+s was changed, the control logic was capable of controlling the operation of the fog cooling system with appropriate tf. Short tf+s would contribute to minimize not only changes in Tdi and RHi, but also foliage wetting. At a constant tf, the control logic could lengthen duration of fog cooling system stand-by (ts) that also prevented excessive fogging when the potential evaporation of sprayed water inside the greenhouse was low. The proposed control logic can be implemented for controlling the operation of a fog cooling system not only at constant tf but also at constant ts.