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Increased Resistance to Flow and Temperature-rise Resulting from Dust Accumulation on Greenhouse Insect-proof Screens

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  024040,  2002 ASAE Annual Meeting . (doi: 10.13031/2013.10475) @2002
Authors:   Raphael Linker, Moshe Tarnopolsky, Ido Seginer
Keywords:   natural ventilation, fan ventilation, 50-mesh screen

Insect-proof screens increase the resistance to ventilation flow across a greenhouse. The pressure drop across a clean 50-mesh screen is approximately 10 times the dynamic pressure of the approach velocity. While this is negligible relative to the pressure drop created by fans, it is a significant fraction of the wind-induced pressure drop. In naturally ventilated greenhouses, the problem is further aggravated by the accumulation of dust, which may increase the resistance of a screen by an order of magnitude.

Measurements in a 50m2 greenhouse showed that the loss coefficient of a 50-mesh screen increased from 12 when clean to 200 after two months of continuous fan ventilation. An approximate analysis of the problem showed that in naturally ventilated greenhouses, reduced ventilation due to dust accumulation, could double the intended temperature-rise.

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