Prediction of leakage rate of a greenhouse using computational fluid dynamics

T. Kuroyanagi
Air leakage causes loss of heat and carbon dioxide from greenhouses. The magnitude of the leakage is evaluated by the tracer gas method or energy balance method, but these methods often require cost and time. An alternative to these experimental methods is proposed in this study. The feasibility of computational fluid dynamics (CFD) for the prediction of leakage rate of a greenhouse was investigated. The procedure commenced with the calculation of the external pressure coefficient of each surface of the greenhouse using CFD simulation. Subsequently, the leakage rate was calculated numerically, as well as the internal pressure coefficient, using a model that estimates the leakage airflow through apertures, which is induced by the difference between the external and internal pressures on either side of a wall. For validation, a single-span greenhouse (floor area: 6×14 m, and height: 3.5 m) was used. A net-covered windbreak (a porosity of 0.604) was used to investigate the robustness of the model; the influence of the presence of obstacles on the accuracy of the predicted leakage rate was studied. The simulation was validated by comparing with the information available in literatures and the leakage measurements. The leakage rate predicted based on CFD simulation has similar levels as the values obtained from leakage measurements using the concentration decay method.
Kuroyanagi, T. 2017. Prediction of leakage rate of a greenhouse using computational fluid dynamics. Acta Hort. (ISHS) 1170:87-94
CFD, numerical model, wind pressure coefficient, concentration decay method

Acta Horticulturae