ISHS Acta Horticulturae 633: XXVI International Horticultural Congress: Protected Cultivation 2002: In Search of Structures, Systems and Plant Materials for Sustainable Greenhouse Production
THE EFFECT OF ROOF INCLINATION ON THE CONDENSATION BEHAVIOUR OF PLASTIC FILMS USED AS GREENHOUSE COVERING MATERIALS |
| Authors: | K. Gbiorczyk, P.J. Sonneveld, G.P.A. Bot, B. von Elsner |
| Keywords: | drop-like, contact angle, antifog, dripping behaviour, light reflection |
| Abstract:
Different antifog greenhouse films were investigated concerning their condensation behaviour at different roof inclinations in comparison to a standard copolymer LDPE film. The disadvantage of plastic films used as greenhouse covering in comparison to glass is their hydrophobic behaviour. Drop-like condensation leads to light reflection and to droplets falling onto the plants. Therefore special additives are integrated into the film in order to change the condensation into a water film condensation. The problem is that no standardised testing method for an objective evaluation of the antifog effect of greenhouse films exists. The plastic films for greenhouse covering were characterised by studying the condensed water pattern formation with an IR-camera and measuring relevant physical properties of the film influenced by the condensation, for example, the light reflectance with a reflectometer. The measurements on the greenhouse films were performed under laboratory conditions with a specially designed contact angle measurement device and an inclinable hotbox located in a cold room. It was possible to predict the critical roof inclination of a film concerning the sliding and dripping of droplets with the measurement of single droplets. A certain inclination angle exists also for the antifog films below that the condensate drips down onto the plants. This angle is different for each material. The reflectance measurements showed that there was a critical inclination for a non-wettable material like the standard LDPE-film but not for the tested antifog films. | |
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