Influence of vent design on greenhouse microclimate during dehumidification with simultaneous heating and ventilation

Abstract

The influence of greenhouse vent configuration on greenhouse microclimate and energy consumption when natural ventilation was used for greenhouse dehumidification was numerically analysed using a computational fluid dynamics model after its experimental validation. Two commonly found vent configurations (roll-up type and pivoting door type) were tested in a tunnel greenhouse with a mature tomato crop. The simulations were two dimensional and the solution was obtained in two steps. First a converged solution under steady-state conditions was obtained. Then, the flow was considered unsteady air humidity inside the greenhouse was assumed to be 90% and air temperature 20°C whereas the corresponding outside climate variables were 50% and 10°C. Ventilation openings were activated and air humidity and temperature were decreased in the greenhouse at a rate depending on the local value of the air velocity inside the greenhouse. The different vent arrangements resulted in different airflow patterns inside the greenhouse. As a result of the different airflows, the temperatures and humidities inside the greenhouse were reduced accordingly during dehumidification. The ratio of latent to sensible heat exchange during the dehumidification process was chosen as the criterion in order to evaluate the energy efficiency of each ventilation configuration. The roll-type vent configuration had the best energy performance.