INVESTIGATION OF A SPRAY COOLING SYSTEM IN A PLASTIC-FILM GREENHOUSE

A new evaporative cooling system for greenhouses, for use in arid countries, has been developed and is described. The object has been to examine overall performance, in terms of the thermodynamic condition (temperature and humidity) of the air entering the system, heat exchange between air and the cooling spray (using concurrent flow, counter-current flow and a combination of these two) and nozzle pressure (which determines the amount of spray used). Measurements were made using a range of instruments, including ventilated psychrometers, thermocouples, solarimeters and hydrometers, installed in appropriate locations both inside the greenhouse and on the outside of the cooling system. The experiment showed that high heat exchange efficiencies, approaching 100%, could be achieved with the air and spray in counter-current flow. Optimum operating parameters were found to be a nozzle pressure of 2 × 105 Pa and a water/air coefficient of 0·09 kg water/kg air. A mechanical pumping power of 144 W was required. © 1992 Silsoe Research Institute.