Author： Pieters J.G. deltour J.M.
Publisher： Academic Press
ISSN： 0021-8634
Source： Journal of Agricultural Engineering Research, Vol.68, Iss.2, 1997-10, pp. : 125-137
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Abstract
Yearly auxiliary heating requirements were simulated for four greenhouses, covered with different cladding materials, in which a tomato crop was grown. The simulations were carried out both including and neglecting the condensation and evaporation phenomena inside the greenhouse. It is shown that under a temperate maritime climate, values for the heating requirements obtained by the model without allowing for condensation are under estimated by about 15% for glasshouses and over estimated by about 20% for a polyethylene-covered greenhouse.Condensation on the cover is shown to be the far most important sink for water vapour for the inside air during night and amounts to between 85 and 89% depending on the cladding material. Whereas the evaporation mass fluxes from the cover are found to be very low and to be almost the same for all claddings, condensation fluxes are demonstrated to be much higher and much more dependent on the cladding material.Neglect of condensation is shown to have almost no effect on the simulated inside air temperature of an active greenhouse, i.e. a greenhouse whose inside climate is controlled actively by heating and ventilating, while it leads to overestimates of the relative humidity by about 10%, the errors being somewhat smaller for greenhouses with low emissivity cladding during daytime. It also results in overestimates or underestimates of the vegetation temperature, according to the far-infrared radiation properties of the cladding material, low transmittances giving rise to overestimates. Copyright 1997 Silsoe Research Institute
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