Simulação e comparação de sistemas de ventilação por meio da dinâmica de fluidos computacional em ambiente protegido

Abstract

The objective of this study was to model and to simulate, using CFD techniques, a greenhouse trough the interaction of the external environment with the internal environment, and thus describe the main monitored variables: solar radiation (Qg, W m-2), temperature of the air (Tar, °C) and relative humidity (RH%). After the validation of these models, to develop simulations of two ventilation systems (a) Natural ventilation system and (b) evaporative heat exchange system through the soil to compare and predict the microclimatic variations. The study was conducted in two phases. First, monitoring and analysis of meteorological variables of a environment located in Recife, on the campus of Rural Federal University of Pernambuco, with plastic cover (low density polyethylene) and geometric characteristics of 7.0 m wide, 21.0 m long, 3.0 m high-ceiling and 4.5 m in total height. The second phase consisted in numerical modeling of greenhouse finite volumes and thus to validate the model using the experimental data, and finally to simulate the two ventilation systems. The modeling results generally have shown good agreement in the comparative relationships between measured and simulated values, with coefficients of determination (R²) of 0.9722 for Qg, 0.9347 for Tar, and 0.9392 for RH. In the simulations of the ventilation systems, the indirect evaporative system using heat exchangers through the soil have shown the best performance in reducing Tar at 4 °C and reduced by 15% the RH. The natural ventilation system by opening the roof axis was able to reduce the Tar by 1 °C and kept the relative humidity stable. It was concluded that with the use of CFD techniques it was possible to model and to characterize the greenhouse, and to simulate ventilation systems in order to improve the conditions of temperature and relative humidity.