Ventilation Performances of a Large Canarian Type Greenhouse Equipped With Insect-Proof Nets

Fatnassi, H.; Boulard, T.; Bouirden, L.; Sappe, Gilbert

doi:10.17660/actahortic.2002.578.8

Cited by 25 publications

(32 citation statements)

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“…These finding are similar to what have been found by other authors that the combination of roof and side openings increases air velocity hence the air renewal rate (Bartzanas et al, 2005;Fatnassi et al, 2001;Harmanto et al, 2006).…”

Section: Influence Of Ventilation Strategy On Air Renewal Ratessupporting

confidence: 93%

Effects of Different Ventilation Strategies on the Microclimate and Transpiration of a Rose Crop in a Reenhouse

J¹

2013

GJSETR

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The study was aimed at reducing internal air temperatures of a greenhouse shelter as this is one of the main problems facing greenhouse management in warm climates such as in Zimbabwe. The water vapour balance method was used to evaluate the ventilation rate and the results were employed in calibrating and validating the ventilation sub-model of the greenhouse climate model, the GDGCM model, in a naturally ventilated three span Azrom type greenhouse in Zimbabwe. Two ventilation regimes namely: configuration with roof vents only with closed side vents and configuration with both side vents and roof vents open, were investigated. Crop transpiration was estimated using the Penman-Monteith method. The model was fitted to experimental data for ventilation rates, and the parameters for the model, the discharge and wind effect coefficient were determined using statistical analysis. The results showed that there was a good fit between measured and predicted values (R 2 = 0.702 and 0.729) for the model on the two ventilation regimes. The air renewal rate was found to be influenced by the nature of ventilation regime in place. The model simulation revealed that the greenhouse has higher air renewal rates for the configuration with both roof and side vents. The greenhouse internal air temperature was reduced significantly for the latter configuration as it had lower simulated air temperatures than the former.

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Section: Influence Of Ventilation Strategy On Air Renewal Ratessupporting

confidence: 93%

Effects of Different Ventilation Strategies on the Microclimate and Transpiration of a Rose Crop in a Reenhouse

J¹

2013

GJSETR

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“…Since the air in both greenhouse types was the same, the difference must be solely due to roof shape and associated differences in aero-dynamics. According to earlier work, under low wind speeds where natural buoyancy dominates, a combination of roof and side vents were required to maintain an effective rate of air exchange (Kittas et al, 1997;Fatnassi et al, 2002;Kalsoulas et al, 2006). This fact was supported by the lowest temperature difference found for the greenhouse with continuous ridge vents.…”

Section: Discussionmentioning

confidence: 97%

“…The main drawback of this type of vents is the low degree of internal environment control due to inadequate wind-driven ventilation, particularly under less windy periods at low and mid elevations (up to 1000 m above sea level) and in farmer fields with tall vegetation (reducing the impact of winds). Covering of vents with insect screens further limits the air-flow rates (Fatnassi et al, 2002). Under warm weather, at least 30% ventilation area (with respect to floor area) should be provided for proper ventilation under hot still conditions (Hanan, 1998;Nelson, 1998).…”

Section: Introductionmentioning

confidence: 99%

Natural ventilation in insect screened single span greenhouses under warm weather

Weerakkody¹,

Amarathunga²,

Warnakulasooriya³

et al. 2010

International Journal of Biological and Chemical Sciences

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The ventilation rates of different types of ridge vents in combination with insect-screened side vents were assessed in single greenhouses in terms of the difference in temperature and humidity inside and outside under tropical conditions. The A-frame (slanted roof) was comparatively advantageous over the conventional arch frame (curved roof) for keeping daytime temperature lower in single span greenhouse with insect-screened side vents (mesh size: 1 by 1 mm) and without roof vents. The inclusion of ridge vents further reduced the internal temperature and relative humidity (RH) in the A-frame greenhouse during the daytime. The opening area of the ridge vent within the range between 9.3% and 14% (of the floor area) did not significantly change the ventilation based internal temperature and RH when operated under low wind speeds (0.5 ± 0.5 m s -1 ). Meanwhile the effect of ridge orientation, with respect to wind direction, on greenhouse ventilation was not obvious in terms of temperature or RH under inconsistent wind directions and low wind speeds. Greenhouse ventilation positively responded to low winds (0.25 m s -1 ) by reducing internal temperature as well as RH. However, the response to a further increase in wind speed from 0.25 to 0.5 m s -1 was not significant. Based on climate control characteristics an A-frame single-span greenhouse design with double sided alternate ridge vents and insect-screened side vents could be appropriate for tropical climates under low wind speeds and inconsistent wind directions as a cost effective and user-friendly greenhouse design. Particularly, it is highly applicable for the small-scale controlled environment vegetable production in mid and low elevations in the wet zone of Sri Lanka.

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“…Papadakis et al (1996) found that the thermal effect was fundamental for winds of less than 1.8 m s -1 , while Boulard & Baille (1995) set this speed at 1.5 m s -1 and Sase et al (1984) at 1 m s -1 . Other researchers have suggested that in greenhouses equipped with roof vents the thermal effect can be neglected for wind speeds of over 2 m s -1 (Boulard & Baille, 1995), and this was also suggested for a greenhouse with side and roof vents (Fatnassi et al, 2002). For the latter type of greenhouse, Kittas et al (1997) found that the thermal effect is important when the ratio u o /∆T io 0.5 is less than 1, while Bot (1983) set the limit at 0.3.…”

mentioning

confidence: 97%

“…Although many authors have obtained the coefficients C d and C w that allow the semi-empirical models to be applied (Kittas et al, 1996Papadakis et al, 1996;Boulard et al, 1997;Fatnassi et al, 2002;Teitel et al, 2008;Molina-Aiz et al, 2009, there is still considerable debate as to the exact relationship between the wind and thermal effects in the natural ventilation of greenhouses. Papadakis et al (1996) found that the thermal effect was fundamental for winds of less than 1.8 m s -1 , while Boulard & Baille (1995) set this speed at 1.5 m s -1 and Sase et al (1984) at 1 m s -1 .…”

mentioning

confidence: 99%

Determinación de los patrones de flujo de aire en un invernadero multitúnel mediante anemometría sónica

López¹,

Valera²,

Molina-Aiz³

et al. 2012

Span. j. agric. res.

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The present work describes a methodology for studying natural ventilation in Mediterranean greenhouses using sonic anemometry. The experimental work took place in the three-span greenhouse located at the agricultural research farm belonging to the University of Almería. This methodology has allowed us to obtain patterns of natural ventilation of the experimental greenhouse under the most common wind regimes for this region. It has also enabled us to describe how the wind and thermal effects interact in the natural ventilation of the greenhouse, as well as to detect deficiencies in the ventilation of the greenhouse, caused by the barrier effect of the adjacent greenhouse (imply a mean reduction in air velocity close to the greenhouse when facing windward of 98% for u, 63% for u y , and more importantly 88% for u x , the component of air velocity that is perpendicular to the side vent). Their knowledge allows us to improve the current control algorithms that manage the movement of the vents. In this work we make a series of proposals that could substantially improve the natural ventilation of the experimental greenhouse. For instance, install vents equipped with ailerons which guide the air inside, or with vents in which the screen is not placed directly over the side surface of the greenhouse. A different proposal is to prolong the opening of the side vents down to the soil, thus fomenting the entrance of air at crop level.Additional key words: buoyancy; insect-proof screens; natural ventilation; wind effect. ResumenDeterminación de los patrones de flujo de aire en un invernadero multitúnel mediante anemometría sónicaEn este trabajo se ha desarrollado una metodología para estudiar la ventilación natural en invernaderos mediterrá-neos mediante anemometría sónica. Los ensayos se han realizado en un invernadero multitúnel de tres módulos situado en el Campo de Prácticas de la Universidad de Almería. Esta metodología nos ha permitido obtener los patrones de ventilación natural del invernadero experimental para los vientos más comunes de la región. También nos ha permitido describir la interacción entre el efecto eólico y térmico, así como detectar deficiencias en la ventilación natural del invernadero debidas al efecto barrera de otro invernadero adyacente (provocando una reducción media en la velocidad del aire en el exterior de la ventana de barlovento de hasta el 98% para u, 63% para u y y, más importante, 88% para u x , la componente de la velocidad del aire que es perpendicular a la superficie de ventilación lateral). Los conocimientos adquiridos en este trabajo nos permitirán mejorar los algoritmos de control del sistema de ventilación. En este trabajo se realizan una serie de propuestas que podrían mejorar sustancialmente la ventilación natural del invernadero. Por ejemplo, se proponen algunas posibles modificaciones de la configuración de las ventanas laterales, buscando una mayor captación del aire exterior: se podría optar por ventanas dotadas de alerones exteriores que dirijan al aire hacia el inte...

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Ventilation Performances of a Large Canarian Type Greenhouse Equipped With Insect-Proof Nets

Cited by 25 publications

References 0 publications

Effects of Different Ventilation Strategies on the Microclimate and Transpiration of a Rose Crop in a Reenhouse

Effects of Different Ventilation Strategies on the Microclimate and Transpiration of a Rose Crop in a Reenhouse

Natural ventilation in insect screened single span greenhouses under warm weather

Determinación de los patrones de flujo de aire en un invernadero multitúnel mediante anemometría sónica

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