Abstract
This study was aimed to investigate the effect of vertical air-circulation fans on air temperature distribution in a greenhouse. In order to observe temperature change before and after the circulation fan was operated, A total of 12 sensors were installed, three sensors at an interval of 2 m horizontally and four sensors at an interval of 1 m vertically. Airflow of vertical circulation fan was predicted using CFD simulation. When the circulation fan was operated, the temperature deviation at 0.5 m and 3.5 m above the ground was reduced from 7.2℃ to 4.2℃. The average temperature at 0.5 m and 1.5 m above the ground increased to 1℃ and 1.2℃, while the average temperature at the height of 2.5 m and 3.5 m above the ground decreased to 0.2℃ and 1℃. In “fan on” condition, the high-temperature air at upper and the low-temperature air at lower was circulated and the temperature at upper becomes lower and the temperature at lower rises. It was found that the distance which the wind reaches depends on the speed of the air circulation fan, if the wind speed is sufficient, the wind reaches up and circulates to 0.5 m above the ground. The overall findings of this study showed that there was significant effects making uniform air temperature distribution in a greenhouse by operating vertical air-circulation fans. And this study suggested that the speed of the circulation fan should be adjusted according to height of bed and cultivated crops. In hot air heating, the vertical temperature distribution was not uniform and the temperature difference between the upper and lower sides was large.
Figures & Tables
Fig. 1. Blade and exterior of vertical air circulation fan.