Climate dynamic simulations of a cropped greenhouse tunnel

• Published in: Acta horticulturae no. 8931; pp. 581 - 587
• Main Authors: Nebbali, R, Roy, J.C, Boulard, T
• Format: Journal Article
• Language: English
• Published: International Society for Horticultural Science 2011
• Subjects: air flow; canopy; climate; cooling; greenhouses; heat transfer; prediction; relative humidity; temperature; transpiration; wind direction
• ISSN: 0567-7572

This paper describes a dynamic model of a tunnel greenhouse accounting for two major physical processes which have been scarcely tackled up to now: the simulation of both incident solar radiations and thermal inertia of greenhouse ground. The objective of this work is the dynamic prediction of temperature and humidity patterns inside a greenhouse tunnel. Therefore, a 3D model of a tunnel greenhouse with lateral vents and its immediate surrounding has been developed using the Fluent Computational Fluid Dynamics code. Several dynamic boundary conditions have been considered: external wind varying in direction; daily variations of incident global solar density of radiation and temperature at ground surface. Accordingly, the ground located below the greenhouse was meshed until 1.6 m depth where the temperature can be considered as unchanged. The initial temperature field at ground level has been determined from a semi-analytical model based on experimental data and the temperature variations in the ground were determined with the finite volume method. Simulations have been performed for different external boundaries (including the modelling of short and long waves radiations) corresponding to different day and night times and for various wind directions, the air flow, temperature and relative humidity patterns inside the greenhouse are presented. These results highlight the influence of dynamic boundary conditions on the evolution of inside temperature. Based on the coupling of radiative and convective heat fluxes at crop level, the canopy transpiration has been also quantified for different day time periods and external wind direction. This study demonstrates the ability of the CFD code to simulate the dynamic greenhouse climate evolution with a great realism. It suggests also a possible exploitation for helping to design the greenhouse and dimension the ventilation cooling or heating devices for improving the distributed inside climate for varying outside conditions all the year long.