Numerical simulation of the airflow and temperature patterns in a greenhouse equipped with insect-proof screen in the openings
An analysis of the ventilation process in a tunnel greenhouse equipped with an insect-proof screen in the side openings was performed with the use of a commercial computational fluid dynamics (CFD) package (CFD2000®). The first simulations were carried out with a wind direction normal to the side openings. It was shown that the insect screens significantly reduce the airflow and increase the thermal gradients inside the greenhouse. The maximum air velocity values inside the greenhouse are observed near the openings, whereas the air velocity is the lowest in the middle of the greenhouse. The use of screens in the openings gives rise to a gradual temperature increase from the windward to the leeward opening. With respect to the outside temperature (27°C), the maximum temperature augmentation was 3°C for the greenhouse without screen and up to 7°C for the greenhouse with screens. Yet, the results show also that the screens induce a better air mixing in the greenhouse. Finally, in order to illustrate the opportunities offered by the use of the CFD packages for improving the greenhouse design characteristics, the effect of different wind speed and directions on the inside air flow and temperature patterns was investigated. It was shown that the wind direction considerably affects the climatic conditions in the greenhouse (contrasted air flow and temperature patterns were observed for various wind regimes) especially when the greenhouse is equipped with insect screens. However, it must be noticed that the CFD packages only gives a qualitative picture of the greenhouse microclimate, further experimental validations being needed to confirm the predictive accuracy of the simulation results.