TWO-DIMENSIONAL NUMERICAL SIMULATION OF NATURAL VENTILATION IN A MULTI-SPAN GREENHOUSE

The natural ventilation system for a four and one-half span commercial greenhouse was evaluated using acomputational fluid dynamics (CFD) model, Fluent 4.3. Wind direction, wind speed, vent opening sizes, and the presenceof plants on benches were all evaluated for their influences on natural ventilation rates and airflow distributions.Considering a target ventilation rate of 0.75 to 1.0 volume per minute (A.C. min 1 ) for a comparable ventilation system,the greenhouse was predicted to achieve an optimum natural ventilation rate of 0.75 A.C. min 1 when the wind speedsfrom the west were 2.4 m s 1 and 2.1 m s 1 with and without the plants, respectively. This same ventilation rate waspredicted to be obtainable when the wind speeds from the east were 3.6 m s 1 and 3.5 m s 1 with and without the plants,respectively. Considering the full spans called the first, second, third, and fourth span from west to east, the side vent andthe fourth roof vent were predicted to act as primary inlet and largest outlet of airflows, respectively for the west wind.For an east wind, the fourth roof vent was predicted to be the primary inlet and the side vent and first roof vent werepredicted to be the primary outlets.