ISHS Acta Horticulturae 719: International Symposium on Greenhouse Cooling
SIMULATION OF ENERGY TRANSFERS IN A PARTITIONED GLASSHOUSE DURING DAYTIME USING A BI-BAND RADIATION MODEL |
| Authors: | P.E. Bournet, G. Chassériaux, V. Winiarek |
| Keywords: | long and short wave length radiation, radiative and thermal transfers, greenhouse, CFD |
| Abstract:
The climate inside a greenhouse strongly depends on heat transfers between the inside and the outside air. When the transpiration of plants is low, these transfers mainly result from a coupling of convective and radiative exchanges through the cover and ground. Until now, this coupling has been hardly investigated using numerical techniques. Considering a partitioned four-span glasshouse equipped with benches and roof vents, an analysis of the distributed climate inside the building was performed using a Computational Fluid Dynamics (CFD) tool. Simulations were carried out with a 2D turbulence closure model with the Boussinesq assumption. Radiative fluxes were included in the model through the resolution of the radiative transfer equation. The 4 mm thick cover material was meshed in order to monitor its temperature. The optical characteristics of the cover were set by distinguishing short [0-3 µm] and long [3-100 µm] wave length radiation. The validity of the model was first checked by comparing the numerical results with experimental data. Measured and predicted temperatures were in good agreement. The walls absorbed heat from solar radiation and were therefore warmer (7 to 8 K) than the inside air temperature, as predicted by the CFD model. The inside air was about 5 K warmer than the outside air for the three validation cases. Considering that the model was partially validated, further simulations were conducted to analyze the effect of different vent arrangements (windward only, leeward only and a combination of both) both on the climate and ventilation rate inside the greenhouse. The temperature patterns inside the greenhouse were predicted to be significantly influenced by the vent opening configuration. The symmetric case generated a relatively smooth and homogeneous flow inside the greenhouse. Nevertheless, even if though configuration was less efficient than the windward configuration for the air exchange rate, it would be probably preferred because it involves less risk of mechanical damage. | |
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