Using computational fluid dynamics to analyse the CO2 transfer in naturally ventilated greenhouse
Abstract
The purpose of the present study is to analyse the variability of the concentration of CO2 inside greenhouses naturally ventilated using Computational Fluid Dynamic simulations and experimental measurements. The photosynthesis of two tomato crops growing in coconut fibre substrate (leaf area index of 0.29 and 0.97 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 cells 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 and the crops were simulated as porous media. Experimental measurements were carried out in multispan and Almer\'{i}a type greenhouses. Inside air CO2 concentration was measured using 6 non-dispersive infrared (NDIR) sensors. Temperature and humidity measurements were taken at 12 locations, while 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. Inside concentration of CO2 ranged from 410 ppm in the middle of the greenhouse to 220 ppm inside the tomato canopy. The measured photosynthesis rates of the tomato crops were 7.6-15.8 A μmol CO2 m–2 s–1 (equivalent to 11.4-20.0 kg CO2 ha–1 h–1).
Molina-Aiz, F. D.; Norton, T.; López, A.; Reyes-Rosas, A.; Moreno, M. A.; Marín, P.; Espinoza, K. & Valera, D. L. Using computational fluid dynamics to analyse the CO_2 transfer in naturally ventilated greenhouse Acta Horticulturae, International Symposium Models for plant growth, environment control and farming management in protected cultivation (HORTIMODEL), International Society for Horticultural Science, 2016, 9-10