Three-dimensional numerical simulation of the thermal and aerodynamic behavior of a roof structure built on a slope and used for horticultural production

In tropical countries, part of the horticultural production is carried out in hillside soils. In recent years, due to the adverse effects of climate change and other biotic factors that limit and affect agricultural production, the use of roof structures has been promoted as a technological means to improve production in this type of production system. The microclimate study of structures built on slopes is scarce, therefore farmers continue to build the same type of structure without technical design criteria and without knowing if the microclimate conditions generated are suitable for the crops. In the present research work, an experimentally validated 3D CFD numerical model was implemented to analyze air flows and spatial temperature behavior in a roof structure built on a site with broken topography. The results obtained allowed us to find that the air flows are strongly affected by the longitudinal and transversal slopes of the land, which produces low ventilation rates that generate thermal gradients above 8 °C and highly heterogeneous thermal behavior, factors that are not suitable for horticultural production

Diseño y evaluación climática de un invernadero para condiciones de clima intertropical de montaña

En Colombia la optimización del diseño de los invernaderos no ha tenido mayor relevancia, o los trabajos realizados principalmente en el sector floricultor no han tenido trascendencia y en consecuencia un alto porcentaje de las estructuras existentes presentan deficiencias en su ventilación, generando así microclimas inadecuados para los cultivos restringiendo su potencial productivo. El objetivo del trabajo fue el de estudiar la eficiencia de variantes introducidas a la ventilación de un invernadero multi-túnel disponible en el mercado mediante simulaciones numéricas empleando el método de dinámica de fluidos computacional (CFD). A partir de un modelo comercial se diseñaron dos variantes experimentales realizando cambios estructurales y de orientación de las ventanas cenitales fijas. Los tres diseños de invernaderos fueron sometidos a simulaciones CFD-2D por computador con el propósito de maximizar los índices de renovación de aire, mejorar el movimiento del flujo de aire en toda la estructura y buscar una homogeneidad en el microclima. El diseño más adecuado fue aquel que presentó un índice de renovación de aire suficiente para garantizar un adecuado control de los excesos de temperatura y humedad a través de la ventilación natural combinada por efecto eólico y térmico. Este diseño generó además el microclima más homogéneo dentro de la zona de cultivo. Adicionalmente se realizó una evaluación climática del invernadero real mediante el uso modelos de simulación CFD-3D, donde se pudo comprobar que el invernadero construido generaba las condiciones micro climáticas adecuadas para el crecimiento y desarrollo del cultivo de pimentón. Este modelo CFD-3D fue validado posteriormente mediante el análisis de variables climáticas reales mediante técnicas geoestadísticas.Abstract In Colombia, the optimization of greenhouses design has not had greater relevance, neither the work performed by the flower industry, consequently a high percentage of the existing structures have ventilation deficiencies that generate inadequate microclimates restricting the crop production potential. The objective of this work was to study the efficiency of ventilation variants introduced to a commercial multi-tunnel greenhouse through numerical simulations using the computational fluid dynamics (CFD) method. Starting with the commercial prototype, two greenhouse variants including structural and orientation changes of the fixed ridge ventilation were designed. The three greenhouse designs underwent 2D CFD-simulation in order to maximize air exchange rates, to improve the airflow movement across the structure and to homogeneize the internal microclimate. The most suitable design was the one that presented a renewal rate sufficient to ensure adequate control of overheating and moisture through natural ventilation combined by wind and thermal effect. This design also generated the most homogeneous microclimate within the crop area. Additionally, a climate assessment was performed for the real greenhouse using CFD-3D simulation models, where it was found that the greenhouse generated microclimatic conditions suitable for sweet pepper growth and development. This CFD-3D model was subsequently validated by analyzing the observed climate variables by geostatistical techniques.Maestrí

Microclimatic behavior of a screen house proposed for horticultural production in low-altitude tropical climate conditions

In developing countries, horticultural production in low-altitude tropical climate conditions is often limited by biotic and abiotic factors. In these countries, the implementation of highly technical greenhouses is not feasible due to economic, social and cultural issues related to farmers. Therefore, one of the alternatives that has taken a great boom is the use of screen house structures (SH), although information on the microclimatic behavior of these is still limited. The objective of this research was to use an experimentally validated 3D CFD numerical simulation model to study the thermal behavior and airflow patterns in an SH located in the Colombian Caribbean region during the daytime hours (6:00 to18:00 h). The results obtained showed that the air flow patterns inside the SH showed speed reductions of up to 68% with respect to the speed of the external wind. It was also found that the thermal behavior inside the SH was quite homogeneous, the average temperature values in the structures ranged between 23.9 and 39 °C and the difference with external environment temperature did not exceed 1.8 °C. It was concluded that the implementation of this type of structure could be an useful technological tool for the optimization of horticultural production in low-altitude tropical climate regions.In developing countries, horticultural production in low-altitude tropical climate conditions is often limited by biotic and abiotic factors. In these countries, the implementation of highly technical greenhouses is not feasible due to economic, social and cultural issues related to farmers. Therefore, one of the alternatives that has taken a great boom is the use of screen house structures (SH), although information on the microclimatic behavior of these is still limited. The objective of this research was to use an experimentally validated 3D CFD numerical simulation model to study the thermal behavior and airflow patterns in an SH located in the Colombian Caribbean region during the daytime hours (6:00 to18:00 h). The results obtained showed that the air flow patterns inside the SH showed speed reductions of up to 68% with respect to the speed of the external wind. It was also found that the thermal behavior inside the SH was quite homogeneous, the average temperature values in the structures ranged between 23.9 and 39 °C and the difference with external environment temperature did not exceed 1.8 °C. It was concluded that the implementation of this type of structure could be an useful technological tool for the optimization of horticultural production in low-altitude tropical climate regions

Evaluación del comportamiento poscosecha de uchuva provenientes de sistemas de producción convencionales y agroecológicos

The production of cape gooseberry (Physalis peruvianaL.) in Colombia has a high socioeconomic interest due to its commercial potential and the large number of small-scale producers that make up the production system. The growing areas in Colombia are located on the cold thermal floors of the departments of Boyaca, Cundinamarca and Antioquia. Recently, in order to seek sustainability in agricultural production, agroecological production has had a growing increase in areas where this type of crop is established. Therefore, the objective of this research was toevaluate and compare the postharvest behaviors of cape gooseberry fruit, obtained under two agricultural production systems (conventional and agroecological) established under climatic conditions of the savanna of Bogota. The methodology consisted of the measurement and quantification of the main physicochemical variables: weight, equatorial diameter, firmness, pH, total soluble solids, acidity, respiration and weight loss during the different stages of maturity. These values were compared in reference to the provisions of NTC 4580. The results obtained for each property showed significant differences between each productive system and each state of maturity evaluated, finding a higher sensitivity to postharvest deterioration in fruits obtained through agroecological productionLa producción de uchuva (Physalis peruviana L.) en Colombia tiene un alto interés socioeconómico por su potencial comercial y el amplio número de productores de pequeña escala que integran el sistema productivo. Las zonas de cultivo en Colombia están localizadas en los pisos térmicos fríos de los departamentos de Boyacá, Cundinamarca y Antioquía. Recientemente, con el fin de buscar la sostenibilidad en la producción agrícola, la producción agroecológica ha tenido un creciente aumento en las zonas donde se establece este tipo de cultivo. Por lo tanto, el objetivo de esta investigación fue evaluar y comparar los comportamientos postcosecha del fruto de uchuva, obtenido bajo dos sistemas de producción agrícola (convencionales y agroecológicos) establecidos bajo condiciones climáticas de la sabana de Bogotá. La metodología consistió en la medición y cuantificación de las principales variables fisicoquímicas: peso, diámetro ecuatorial, firmeza, pH, sólidos solubles totales, acidez, respiración y pérdida de peso durante los distintos estados de madurez. Estos valores fueron comparados en referencia a lo establecido en la NTC 4580. Los resultados obtenidos para cada propiedad mostraron diferencias significativas entre cada sistema productivo y cada estado de madurez evaluado, encontrando una sensibilidad más elevada al deterioro postcosecha en los frutos obtenidos mediante producción agroecológica