INFLUENCE OF EVAPORATIVE COOLING SYSTEM ON MICROCLIMATIC CONDITIONS OF A NURSERY SHADED GREENHOUSE

In this research trail an attempt has been made to analyse the thermal gradient being developed along the direction of the airflow of evaporative cooling system based on cooling pads and extracting fan. A small shaded gable-even-span greenhouse was used as a nursery for germinating seeds of sweet colour pepper and growing the seedlings until transplanting. The experimental work was carried out under the climatic conditions of eastern area of coastal delta, Egypt (latitude angle of 31º 02' 41" N, longitude angle of 31º 21' 55" E, and mean altitude above sea level of 16 m), during summer season of 2013.High temperature gradients of this type can markedly affect seedlings growth, and growers often combine evaporative cooling system with shading. To predict the temperature gradients along a small greenhouse, a simple climatic model was proposed which incorporates the effect of ventilation rate, roof shading, and plant evapotranspiration rate. In order to validate the proposed model, different measurements were accomplished in a small shaded greenhouse equipped with cooling pads and extracting fan.
Experimental data revealed that the evaporative cooling system was able and adequate to keep and maintain the greenhouse indoor air temperature at desired level. The model was validated by fitting measured air temperatures after cooling pads directly, at the middle and before the extracting fan of the greenhouse. It was used to study: the influence of different cooling air temperatures combined with shading on the air temperature profiles along the greenhouse length, and the influence of outside air temperature and relative humidity on the effectiveness of the evaporative cooling system. The proposed model is sufficiently accurate to improve the design and the management of the evaporative cooling system. Due to the optimal level of microclimatic conditions of the shaded greenhouse, the sweet colour pepper seeds being germinated after 8 days from the sawing operation, and the seedlings reached to the transplanting stage after 6 weeks.