A Simulation Model for Functional Design of Insect-Proof Greenhouses for the Humid Tropics

Abstract

A simulation model based on energy and mass balance method was developed in MATLAB\SIMULINK in order to predict the effect of insect-proof screen properties on climate in naturally ventilated greenhouses in the humid tropics. The model uses the four commonly measured weather parameters (wind speed, global solar radiation, air temperature and relative humidity) as input variables. The model was used to evaluate the effects of discharge coefficients (Cd) and area of insect-proof screen materials on greenhouse climate. The discharge coefficients of the insect-proof screening materials were determined by relating static pressure drop and airflow rates using the Bernoulli and continuity equations. External and greenhouse climate measurements were made at the Asian Institute of Technology (AIT) campus in Bangkok, Thailand. The internal climate measurements were made concurrently in two similar, naturally ventilated greenhouses covered with different insect-proof screens on ventilation openings. Tomato (Lycopersiconesculentum ‘KingKongII’) plants were grown in the greenhouse during the experimental period. Model predictions of greenhouse air temperature were then compared to the measurements from the two greenhouses and good agreement was achieved. The results show that insect-proof screens with discharge coefficients between 0.2 - 0.3 would provide adequate ventilation for the screened greenhouse prototype investigated in this study. Keywords: Energy and Mass Balance Model, Insect-proof Screens, Greenhouses, Humid Tropics