ISHS Acta Horticulturae 797: International Workshop on Greenhouse Environmental Control and Crop Production in Semi-Arid Regions
IMPROVEMENT OF HUMAN THERMAL COMFORT IN GREENHOUSES WITH INSECT- PROOF SCREENS |
| Authors: | T. Shimazu, T. Ikeda, H. Hamamoto, T. Okada, K. Tanaka |
| Keywords: | forced airflow, greenhouse ventilation, insect-proof screen, thermal comfort, wet-bulb globe temperature |
| DOI: | 10.17660/ActaHortic.2008.797.26 |
| Abstract:
Although fine-mesh screens incorporated into greenhouse openings can prevent the penetration of insect pests, increasing air temperature and stagnation of air movement in the greenhouse due to ventilation limitation is unsuitable for plants cultivation and thermal comfort of growers during summer. Grower thermal comfort in greenhouses with insect-proof screens was improved by the combination of chimney effect ventilation and forced airflow directed onto growers. The heat stress potential to growers was evaluated by wet-bulb globe temperature (WBGT) measured at a height of 1.5 m in centre of greenhouses. WBGT in a single-span pipe greenhouse equipped with insect-proof screens in both side openings (0.6 mm mesh size) and roof windows (1.0 mm mesh size) was compared with the one in same type greenhouse without roof windows (control). WBGT in the greenhouse with roof openings was lower than that in control when mean wind velocity of outside was below 0.5 m s-1 on high solar radiation period, while WBGT difference between both greenhouses became small during above 1.5 m s-1 of mean wind velocity of outside. However, the combinations of chimney-effect ventilation and forced airflow directed onto the grower decreased WBGT by 3~5°C compared with control, even if mean wind velocity of outside was above 1.5 m s-1. Consequently, this method was available for curtailment of the time period that it was impossible to work in safe thermal environment (WBGT>32.5°C) in the screened greenhouse during summer. | |
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