Numerical modelling of an earth-air- tunnel assisted single span saw-tooth greenhouse for tropical climate

In tropical conditions the greenhouse temperature rise above the advised range at crop height is a major issue. In the present research work, thermal performance of Earth Air tunnel Heat Exchanger (EATHE) assisted single span saw-tooth greenhouse was assessed using indigenously developed code and commercial computer program (ANSYS-Fluent). The numerical model was first validated with published and own experimental data. The effectiveness of coupling EATHE to control inside temperature of the greenhouse was assessed for different side vent opening scenario. The air movement caused by wind and stack effect in greenhouse was an important factor that affected the uniformity of greenhouse temperature. Maximum temperature was observed near the ground because solar radiations transmitted through the greenhouse cover were absorbed by the soil. For greenhouse without EATHE, the inside average temperature remained above 45 degrees C (ambient temperature) as no cooling mechanism was deployed. On the other hand for EATHE assisted greenhouse, optimum plants growth temper-ature (between 25 and 35 degrees C) was maintained at crop height because the annual variation in the underground soil temperature was much smaller compared to the ambient air temperature. Among various configurations, the best thermal performance for optimum plant growth was obtained when both side vents of greenhouse were connected to EATHE.