Dynamic modeling of the environment in a naturally ventilated, fog-cooled greenhouse

A dynamic simulation model for heat and water vapor transfer in a naturally ventilated, fog-cooled greenhouse was developed to predict the temperatures of air, plant, cover and floor surface and the relative humidity in the greenhouse. Transpiration and evaporation were also predicted. An experiment was conducted on a hot summer day (Aug. 9, 2004) in the Tokyo area to measure the environments inside and outside a glass-covered greenhouse with a floor area of 26m2. The greenhouse was cooled intermittently by spraying water fog at a constant rate of 0.01kgs−1 for different fogging and interval times (0.5min on followed by 1.5min off; 1min on–3min off and 1.5min on–4.5min off). The system of equations of the model was solved numerically by using the predictor–corrector technique for the differential equations and the iteration procedure for the algebraic equation. The input parameters to the model were the meteorological conditions and the thermo-physical properties of the greenhouse cover, plant, air and soil. The predicted results using the present model were compared with the measured values and showed a good agreement at different fogging and interval times.