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

Abstract

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...

Microclimate evaluation of a new design of insect-proof screens in a Mediterranean greenhouse

“…Two 3D and six 2D sonic anemometers were used: half of the total in each sector. The 3D anemometers measured the air velocity over 3 minutes (Molina-Aiz et al, 2009;López et al, 2011López et al, , 2012 at each point in the side vents (Fig. 4c).…”

“…4d). The methodology employed has been explained in greater detail in López et al (2011López et al ( , 2012. The side vent of the northern sector of the greenhouse was partially blocked by a small auxiliary warehouse (Fig.…”

Application of Semi-Empirical Ventilation Models in A Mediterranean Greenhouse with Opposing Thermal and Wind Effects. Use of Non-Constant Cd (Pressure Drop Coefficient Through the Vents) and Cw (Wind Effect Coefficient)

“…Figure 3a,b shows the entrance and exit of air through the roof vent (see the polar histograms), demonstrating the negative interaction of the wind and thermal effects. This flow pattern with opposition of the wind effect and thermal effect in the roof vents, in the same naturally-ventilated three-span Mediterranean greenhouse, was described in more detail, including measurements among the crop lines, in López et al [37]. And, similar flow patterns, in the same greenhouse and with the same methodology, was described in Espinoza et al [24], opening the lateral vents combined with two and three roof vents.…”

Effectiveness of horizontal air flow fans supporting natural ventilation in a Mediterranean multi-span greenhouse

“…The position of the vents in the experimental greenhouse is, therefore, not conducive to natural ventilation, as the two effects oppose each other. This does not occur when the roof vent opens to the leeward side (López et al, 2012a).…”