ISHS Acta Horticulturae 578: International Symposium on Design and Environmental Control of Tropical and Subtropical Greenhouses
EFFECT OF VENTILATOR CONFIGURATION ON VENTILATION IN A TROPICAL CROP PROTECTION STRUCTURE |
| Authors: | R. Kamaruddin, J.I. Montero, B.J. Bailey |
| Keywords: | greenhouse, flow visualisation, temperature, stack effect, wind effect |
| Abstract:
A study of natural ventilation by the wind and stack effects in a single-span tropical crop protection structure (TCPS) was conducted in the laboratory and in the open field. One tenth scale models with different ventilator arrangements made from transparent Perspex were tested in the laboratory. To study the wind driven ventilation, a model was immersed in water containing flow visualisation particles in a transparent flume and the water speed varied to simulate the wind. To study thermally driven ventilation, a second model was immersed upside-down in a transparent tank and a coloured salt solution injected through the floor to simulate the buoyancy flux generated from the floor by solar heating. The water flows in both tests were recorded using a video recorder and the images digitised using a computer program to generate temperature and air speed distributions. A full scale TCPS with similar ventilator arrangements was also constructed and used in the open field and inside a full size glasshouse to verify the wind and thermal effects respectively. Comparing the results showed that natural ventilation rates generated by the models and the full scale TCPS were in reasonable agreement. Ventilation by thermal effects was found to be a function of the temperature difference between the inside and outside of the TCPS, while the wind effect was a function of wind speed. | |
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