Using Computational Fluid Dynamics to analyse the CO2 transfer in naturally ventilated greenhouses

F.D. Molina-Aiz, T. Norton, A. López, A. Reyes-Rosas, M.A. Moreno, P. Marín, K. Espinoza, D.L. Valera
This study analysed the variability of the concentration of CO2 inside greenhouses naturally ventilated using Computational Fluid Dynamic (CFD) simulations and experimental measurements. The photosynthesis of a tomato crop growing in coconut fibre substrate (leaf area index of 0.29 m2 m-2) was calculated using the model of Acock. This model was included in the CFD simulations using a user-defined function (UDF). In each cell of the domain corresponding to the crop, the photosynthesis was computed as a function of the CO2 concentration estimated by the CFD software. Photosynthesis was included as a negative source term in the conservation equation for chemical species. Insect proof screens placed in the greenhouse openings were simulated as pressure-jump and the crop was modelled as porous media. Experimental measurements were carried out in an Almería type greenhouse. Temperature and humidity measurements were taken at 12 locations. CO2 concentration, crop temperature, photosynthesis, evapotranspiration and stomata resistance were recorded with a portable photosynthesis system. Sonic anemometers were used to measure the airflow through the greenhouse openings. The results of CFD simulations were compared with the experimental data and good agreements were observed. The CO2 concentrations ranged from 410 ppm in the middle of the greenhouse to 373 ppm inside the tomato canopy. The measured photosynthesis rates of the tomato crops were 10.3-16.8 μmol CO2 m-2 s-1.
Molina-Aiz, F.D., Norton, T., López, A., Reyes-Rosas, A., Moreno, M.A., Marín, P., Espinoza, K. and Valera, D.L. (2017). Using Computational Fluid Dynamics to analyse the CO2 transfer in naturally ventilated greenhouses. Acta Hortic. 1182, 283-292
DOI: 10.17660/ActaHortic.2017.1182.34
greenhouse, photosynthesis, CFD, natural ventilation, CO2 concentration

Acta Horticulturae