Analysis of the Airflow Characteristics of Greenhouse Screening Materials

Miguel, António F.; Braak, N.J. van de; Bot, G.P.A.

doi:10.1006/jaer.1997.0157

Cited by 76 publications

(47 citation statements)

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“…Earlier Miguel et al (1997Miguel et al ( , 1998 has developed an air suction device for typical characterisation of air pressure differences over screens a different low air velocities. For measurements of air permeability of screens at low velocities this air suction device is used.…”

Section: Wageningen Plant Research Report Xxxxmentioning

confidence: 99%

Energy saving screen materials : measurement method of radiation exchange, air permeability and humidity transport and a calculation method for energy saving

Hemming¹,

Technologie²,

Romero³

et al. 2017

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De doelstellingen van het project waren het kwantifi ceren van in kassen gebruikte scherm eigenschappen (emissie en transmissie voor warmtestraling, luchtdoorlaatbaarheid en vochttransport) en de bepaling van de totale energiebesparing onder gedefi nieerde omstandigheden om de prestaties van verschillende schermen (en leveranciers) met elkaar te kunnen vergelijken. Dit helpt telers om meer informatie te krijgen over relevante scherm eigenschappen en stelt hen in staat om een weloverwogen keuze voor een investering te doen. De resultaten tonen aan dat ondoorlatende schermen en schermen met lage emissie en transmissie voor warmtestraling de hoogste energiebesparing geven. Doorlaatbare schermen geven de hoogste vochtafvoer en de laagste luchtvochtigheid tijdens scherm gebruik zonder de noodzaak voor extra mechanische ontvochtiging. AbstractThe objectives of the project were the quantifi cation of the greenhouse screen properties (emissivity and transmissivity for thermal infrared radiation, air permeability and humidity transport) and the determination of the total energy saving under defi ned conditions in order to be able to compare the performance of different screens (and suppliers) with each other. This helps growers to understand more about screen properties and allows them to make an informed choice of investment. The results show that impermeable screens and screens with low emissivity and low transmissivity for thermal infrared radiation give highest energy saving. Permeable screens give highest transport for humidity and lowest air humidity during screen usage without the need for additional mechanical dehumidifi cation.

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Section: Wageningen Plant Research Report Xxxxmentioning

confidence: 99%

Energy saving screen materials : measurement method of radiation exchange, air permeability and humidity transport and a calculation method for energy saving

Hemming¹,

Technologie²,

Romero³

et al. 2017

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show abstract

“…In order to incorporate this resistance, these screens were modeled by means of the porous medium approach as a source term added to the Navier-Stokes equations. Owing to a lack of wind tunnel facilities, the airflow characteristics of shade screens have to be roughly estimated based on the magnitude orders presented by Miguel et al (1997), as shown in Table 3. Preliminary simulations confirm that these estimations are reliable, owing to the acceptable discrepancies between experimental results and simulations.…”

Section: Numerical Simulationsmentioning

confidence: 99%

“…The first is the analysis of the effect of shade parameter modification (e.g., shade combination, rate and level) on the air temperature, climate heterogeneity, spectral distribution and crop inside the greenhouse (Al-Arifi, 1999;Al-helal, 1998;Kitta et al, 2012;Kittas et al, 2003;Lee and Short, 1998;Montero et al, 2013;Piscia et al, 2012b;Sapounas et al, 2010;Vlamdimirova et al, 1996). The second is the investigations of the physical properties of shade materials (Cohen and Fuchs, 1999;Kittas and Baille, 1998;Miguel et al, 1997) and their impacts on greenhouse climate Kittas et al, 1999;Willits, 2000Willits, , 2001Willits, , 2003.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Climate inside Multi-span Plastic Greenhouses under Different Shade Strategies and Wind Regimes

He¹,

Chen²,

Sun³

et al. 2014

HST

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In this work, the effects of shade combination, shade height and wind regime on greenhouse climate were quantified. A two-dimensional (2-D) computational fluid dynamics (CFD) model was developed based on an 11-span plastic greenhouse in eastern China for wind almost normal to the greenhouse orientation. The model was first validated with air temperature profiles measured in a compartmentalized greenhouse cultivated with mature lettuce (Lactuca sativa L., 'Yang Shan'). Next, the model was employed to investigate the effect of shade combinations on greenhouse microclimate patterns. Simulations showed similar airflow patterns in the greenhouse under different shade combinations. The temperature pattern was a consequence of convection and radiation transfer and was not significantly influenced by shade combination. The use of shade screens reduced air velocity by 0.02-0.20 m･s -1 , lowered air temperature by 0.2-0.8°C and raised the humidity level by 0.9-2.0% in the greenhouse. Moreover, it improved the interior climate homogeneity. The assessment of shade performance revealed that the external shade had good cooling and homogeneity performance and thus can be recommended. Furthermore, the effects of external shade height and wind regime on greenhouse climate parameters showed that external shade screens are suitable for installation within 1 m above roof level. They also demonstrated that, under external shade conditions, greenhouse temperature was reduced relative to unshaded conditions by 1.3°C under a wind speed of 0.5 m･s -1 , whereas it was reduced by merely 0.5°C under a wind speed of 2.0 m･s -1 . Therefore, external shading is more useful during periods of low wind speed.

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“…Así, Miguel et al (1997) y Miguel et al (1998 evaluaron diferentes mallas en un túnel de viento, y encontraron que las mejores correlaciones con la porosidad son las de la ecuación (1) 2)…”

Section: Introductionunclassified

“…En los estudios de Miguel et al (1997), Miguel et al (1998) y Valera et al (2005), la caída de presión fue graficada como una función de la velocidad del aire antes de la malla, y un polinomio de segundo grado fue ajustado a la curva de medición, para calcular la permeabilidad y el factor inercial (Teitel, 2010). Al respecto, Flores-Velázquez y Montero (2008) propusieron diferentes relaciones para K e Y (ecuación 3), basados en datos publicados por Miguel et al (1997), Teitel (2001) 3)…”

Section: Introductionunclassified

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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Analysis of the Airflow Characteristics of Greenhouse Screening Materials

Cited by 76 publications

References 1 publication

Energy saving screen materials : measurement method of radiation exchange, air permeability and humidity transport and a calculation method for energy saving

Energy saving screen materials : measurement method of radiation exchange, air permeability and humidity transport and a calculation method for energy saving

Analysis of the Climate inside Multi-span Plastic Greenhouses under Different Shade Strategies and Wind Regimes

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

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