Study of natural ventilation in a Gothic multi-tunnel greenhouse designed to produce rose (Rosa spp.) in the high-Andean tropic

Abstract

In tropical regions the production of ornamentals is developed exclusively in naturally ventilated plastic greenhouses, which sometimes leads to inappropriate microclimates with high temperatures and humidity that limit the productive development of plants. The aim of this work was to study air flows, temperature distribution and relative humidity inside an alternative greenhouse designed to produce rose (Rosa spp.). Three configurations of ventilation, side ventilation (SV), roof ventilation (RC) and combined roof and side ventilation (RSV) were analyzed. The methodological development was based on the use of a previously validated CFD-2D numerical simulation model, which showed an adequate fit between the measured and simulated data, obtaining MAE and RMSE values for temperature and relative humidity of 0.44 and 0.47 °C, 3.99% and 4.04% respectively. The results obtained for the predominant climatic conditions of the study region showed that the highest ventilation rates were obtained for RSV, with values of 0.044 and 0.182 m 3 m -2 s -1 , this ventilation efficiency propitiated the generation of a homogeneous microclimate, with temperature and relative humidity values adequate to produce rose (Rosa spp). ResumoEstudo da ventilação natural em uma estufa gótica multi-túnel projetada para produzir rosa (Rosa spp.) no trópico alto-andino. Nas regiões tropicais, a produção de plantas ornamentais é desenvolvida exclusivamente em estufas plásticas ventiladas de forma natural, o que significa que em algumas ocasiões microclimas inadequados são gerados com altas temperaturas e umidade que limitam o desenvolvimento produtivo das plantas. O objetivo deste trabalho foi estudar os fluxos de ar, a distribuição de temperatura e umidade relativa do ar dentro de uma estufa alternativa projetada para a produção de rosa (Rosa spp.). Três configurações de ventilação, ventilação lateral (SV), ventilação de telhado (RC) e telhado combinado e ventilação lateral (RSV) foram analisadas. O desenvolvimento metodológico baseou-se na utilização de um modelo de simulação numérica CFD-2D previamente validado, que mostrou um ajuste adequado entre os dados medidos e simulados, obtenção de valores de MAE e RMSE para temperatura e umidade relativa de 0,44 e 0,47 ° C, 3,99 e 4,04% respectivamente. Os resultados obtidos para as condições climáticas predominantes da região de estudo mostraram que as maiores taxas de ventilação foram obtidas para o RSV, com valores de 0,044 e 0,182 m 3 m -2 s -1 , essa eficiência de ventilação propiciou a geração de um microclima homogêneo, com valores de temperatura e umidade relativa adequados para a produção de rosa (Rosa spp.). Palavras-chave: Microclima, taxa de ventilação, simulação de CFD, temperatura, umidade relativa, volumes finitos.

Contribution to the Sustainability of Agricultural Production in Greenhouses Built on Slope Soils: A Numerical Study of the Microclimatic Behavior of a Typical Colombian Structure

“…For the temperature variable, it was found that the MAE value oscillated between minimum and maximum values of 0.124 • C and 0.346 • C for 6:00 and 13:00 h respectively, while the RMSE values oscillated between 0.140 and 0.397 • C for these same hours. These values found are within the ranges reported in previous studies where CFD models were implemented to determine airflow patterns and thermal distribution in naturally ventilated greenhouses [34,51]. In the case of the air velocity variable inside the greenhouse evaluated, the spatial distribution of the measured and simulated values for each hour was plotted, finding that the experimentally sampled values showed high coincidence with the simulated values (Figure 6).…”

“…The values of the highest normalized velocity agreed with the time when the temperature of the outside environment started to decrease, therefore it can be mentioned that this acceleration of the air flow inside the greenhouse may be strongly associated with the thermal effect of natural ventilation by buoyancy; an effect that generally produces rapid changes in temperature and velocity inside a greenhouse [59]. This buoyancy phenomenon is caused by convective movements generated between the soil and the greenhouse cover, since at that time the soil is the surface of higher temperature due to energy storage throughout the day, while the cover usually cools rapidly to the level of the outside ambient temperature [34,60].…”

“…There are currently a considerable number of studies applied to agricultural investors that have used CFD simulation to analyze thermal distribution [10,21,22], moisture distribution [5,21,23], efficiency of heating systems [24][25][26], the operation of cooling systems [27][28][29] and the microclimate generated as a function of different ventilation configurations [7,12,[30][31][32]. In the specific case of Colombia, the use of CFD and other modelling techniques to determine the behavior of the main greenhouse structures used has been carried out for the specific conditions of the Bogotá savannah and for a topography of flat soils, which is where the ornamental and cut flower industry is generally developed [33][34][35].…”

Experimental evaluation of the thermal and hygrometric behavior of a Colombian greenhouse used for the production of roses (Rosa spp.)

“…When separating the behaviour during the day and the night, it is observed that for the night period the behaviour of the temperature inside the greenhouse was similar to that of the temperature outside, obtaining values of 11.6 and 11.5 °C respectively, on the other hand, for the day period the average value of the temperature inside was 16.9 °C while in the outside 2A). The daytime thermal behaviour can be considered acceptable for rose production between 9 and 16 hours where the temperature value is above the minimum recommended value of 17 °C for rose production, but well below the recommended optimum value of 24 °C, this will result in longer growing cycles (Villagrán and Bojacá, 2019a). It should also be noted that the thermal behaviour at night is not suitable for the production of roses as they have average values of less than 12.5 °C inside the greenhouse, which is below the minimum recommended value for rose production of 14 °C (Reid, 2008).…”

Comportamiento microclimático diurno, en temporada seca, de tres estructuras para agricultura protegida en el trópico seco

“…Las distribuciones espaciales de temperatura y humedad relativa sobre la zona de cultivo en cada una de las estructuras estudiadas mostraron un comportamiento que se puede considerar homogéneo, ya que las diferencias entre los valores máximos y mínimos para cada hora simulada fueron mínimos. Lo anterior se concluye al comparar los resultados de esta investigación con los resultados obtenidos en otros estudios de invernaderos y casa de malla donde para un momento de tiempo específico se reportan diferencias entre zonas en el interior de las estructuras con valores superiores a los 4°C para la temperatura y 15% para la humedad relativa (Flores-Velazquez, Guerrero, López, Montero, & Piscia, 2013;Mesmoudi et al, 2017;Villagrán & Bojacá, 2019b).…”