Flow Through Inclined and Concertina-Shape Screens

Teitel, M.; Liron, O.; Haim, Y.; Seginer, Ido

doi:10.17660/actahortic.2008.801.5

Cited by 15 publications

(9 citation statements)

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“…The use of net coverings in crop production has been shown to mitigate extreme climatic fluctuations and improve canopy vitality [11]. At the same time, net covers provide physical exclusion for insects, thereby reducing the incidence of direct crop damage and insect-transmitted viral diseases [12]. This in turn would reduce the farmer's dependence on chemical pest control.…”

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confidence: 99%

The Assessment of the Use of Eco-Friendly Nets to Ensure Sustainable Cabbage Seedling Production in Africa

et al. 2012

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High seed cost accompanied by poor germination and seedling performance renders cabbage nursery and field production enterprises unsustainable to many small-scale growers in tropical and sub-tropical countries. In most nurseries, adverse ecological conditions and pest damage are among the major factors responsible for poor seedling performance. The objective of this study was to test the potential use of eco-friendly net (EFN) covers as a low cost technology for sustainable cabbage seedling production. The study was a two-season experiment conducted using a randomized complete block design with five replications and two treatments. Treatments were: the standard open field transplant production (control) and transplant production under 0.4 mm mesh polyethylene net covering. EFN covering increased both temperature and relative humidity, enhanced seedling growth and reduced insect pest damage. Seed germination and seedling emergence were under the net covering earlier. Higher seed germination and seedling survival were recorded under the EFN treatment, indicating a potential for reducing the seed requirement per unit area of cabbage production. Seedlings grown under the nets had higher stomatal conductance and leaf chlorophyll content; furthermore, they grew taller, with more leaves within a shorter period of time compared to the control seedlings. The use of EFN in cabbage nurseries offers a sustainable technology for enhancing seedling performance by reducing pest infestation, thereby lowering production cost and improving the grower’s income

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confidence: 99%

The Assessment of the Use of Eco-Friendly Nets to Ensure Sustainable Cabbage Seedling Production in Africa

et al. 2012

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“…As simulation technology and computing power have improved, accuracy and realism in research based on CFD models, has increased as well, by defining more detailed models and by the use of textures that define the materials of the facilities. The use of insect-proof screens in commercial greenhouses is very important as a means of crop protection; even though they reduce natural ventilation, by this, there have been many research efforts to reduce its negative influence (Kittas et al, 2005;Harmanto et al, 2006;Majdoubi et al, 2007;Teitel et al, 2008a). These studies tested different designs in size of the box and tilt and determined the most affected areas within the greenhouse, where the use of porous media allowed its CFD simulation.…”

Section: Main Results Of Cfd Models In Greenhousesmentioning

confidence: 99%

“…Majdoubi et al (2007) found that insect-proof screens significantly reduced airflow, increasing thermal gradients inside the greenhouse by 46%. Using a wind tunnel with screens of different porosity (0.62, 0.52 and 0.4), Teitel et al (2008a) showed that a screen inclined by airflow reduces drag compared to a flow perpendicular to the screen, allowing an increase of 15-30% and 25% in the upper compared with a flat screen. Also, Teitel et al (2009) found that higher speed screens are inclined at 45 ° and decreased to 135 ° tilt.…”

Section: Screens and Ventsmentioning

confidence: 99%

Advances in Computational Fluid Dynamics Applied to the Greenhouse Environment

Flores-Velázquez¹,

Torre-Gea²,

Rico-García³

et al. 2012

Applied Computational Fluid Dynamics

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“…Because of this resistance air velocity, temperature and humidity inside the greenhouses are modified (Fatnassi et al, 2003) and light transmission (von Zabeltitz, 2011) is reduced, adversely affecting the growth and development crop, and favoring the onset of disease (Teitel et al, 2008). Meshes normally used in greenhouses ventilation rate decreased about 40% by anti-insect mesh, and 70-80% in anti-trips meshes (Montero and Anthony, 2000), although this decrease can be higher if the wind speed it is very low (Castilla, 2013).…”

Section: Introductionmentioning

confidence: 99%

Características aerodinámicas de mallas anti-insectos usadas en ventanas de invernaderos en México

Vega

Arias

Cruz

2017

Remexca

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ResumenSe analizaron mediante pruebas de microscopía y en túnel de viento, las características geométricas, porosidad y la caída de presión, respectivamente de siete diferentes mallas comúnmente usadas como barreras físicas en ventanas de invernaderos mexicanos para determinar su efecto sobre la tasa de ventilación, la permeabilidad y el factor inercial. Las mallas se analizaron en la Universidad Autónoma Chapingo en mayo de 2013 y fueron: anti-trips (M1), anti-trips bicolor (M2), anti-áfidos (M3), anti-áfidos bicolor (M4), cenital (M5), rompevientos verde-negro (M6) y anti-áfidos blanca (M7), cuyas porosidades fueron 0. 36, 0.35, 0.47, 0.45, 0.54, 0.29 y 0.43 respectivamente. La geometría de las mallas se realizó midiendo las áreas de los poros con un microscopio óptico, para determinar las porosidades y calcular el descenso de la tasa de ventilación. Posteriormente, las características aerodinámicas más importantes; es decir, permeabilidad y factor inercial, se determinaron usando un túnel de viento para medir la relación entre la caída de presión causada por cada malla y la velocidad del flujo de aire. Los resultados mostraron que la malla cenital (M5) presenta la menor resistencia al flujo de aire con 21% de descenso en la tasa de ventilación, mientras que la malla rompevientos verde-negra (M6) fue de 50%. Los invernaderos en México normalmente usan la malla del tipo anti-áfidos con porosidad entre 0.43 y 0.47 para las ventanas laterales y cenitales. AbstractThey were analyzed by tests microscopy and wind tunnel, geometric characteristics, porosity and pressure drop, respectively seven different meshes commonly used as physical barriers windowing Mexican greenhouses to determine its effect on the ventilation rate, permeability and the inertial factor. The meshes were analyzed in the Chapingo in May 2013 were: anti-thrips (M1), antithrips bicolor (M2), anti-aphid (M3), anti-aphid bicolor (M4), zenithal (M5), green-black windbreaker (M6) and anti-aphid white (M7), whose porosities were 0.36, 0.35, 0.47, 0.45, 0.54, 0.29 and 0.43 respectively. The geometry of the meshes is performed by measuring the areas of the pores with an optical microscope to determine the porosities and calculate the decrease in ventilation rate. Subsequently, the most important aerodynamic characteristics; i. e. inertial factor and permeability were determined using a wind tunnel to measure the relationship between the pressure drop caused by each mesh and the speed of the airflow. The results showed that the zenithal mesh (M5) has the least resistance to air flow with 21% decrease in ventilation rate, while the greenblack windbreaker mesh (M6) was 50%. Greenhouses in Mexico typically use anti-aphid mesh with porosity between 0.43 and 0.47 for the side windows and zenithal type.

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Flow Through Inclined and Concertina-Shape Screens

Cited by 15 publications

References 0 publications

The Assessment of the Use of Eco-Friendly Nets to Ensure Sustainable Cabbage Seedling Production in Africa

The Assessment of the Use of Eco-Friendly Nets to Ensure Sustainable Cabbage Seedling Production in Africa

Advances in Computational Fluid Dynamics Applied to the Greenhouse Environment

Características aerodinámicas de mallas anti-insectos usadas en ventanas de invernaderos en México

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