Comparison of Field Measurements and CFD Simulation for a Naturally Ventilated Multi-Span Greenhouse in Summer

The objectives of this study were to verify full scale computational fluid dynamics (CFD) simulations of temperature distributions for a naturally ventilated multi-span greenhouse and to investigate the influence of roof and side vents configurations on the ventilation performance and greenhouse cooling during the summer. The measurements were carried out in an empty 17-span Venlo greenhouse. The outside weather and the inside environment were measured from July 15 to 24, 2004. The air temperatures were measured at five locations in the central vertical plane of the greenhouse. The measured weather conditions such as wind speed, wind direction, outside air temperature and solar radiation were input in the simulations. Three combinations of roof and side vent openings were compared through field measurements and CFD simulations. Results showed that the temperature distributions were similar for all cases when comparing measurements and CFD simulations. For example, when only the roof vents were open, the measured air temperature differences between inside (T-idb) and outside (T-odb) at a distance from the east side wall of 5.2, 16.2, 27.2, 38.2 and 49.2 in were 6.6 degrees C, 5.6 degrees C, 4.9 degrees C, 5.5 degrees C and 4.2 degrees C, respectively, and CFD-simulated (T-idb - T-odb) were 7.3 degrees C, 5.0 degrees C, 4.3 degrees C, 3.8 degrees C and 3.2 degrees C, respectively. The CFD-simulated ventilation rates indicated that the maximum value was achieved when the roof and side vents were fully open. However, the internal air temperatures in the leeward side of the greenhouse were higher than in the windward side. In contrast, the better temperature uniformity was obtained when the only roof vents were open.