CFD MODELING TO ASSESSING ENVIRONMENT OF A GREENHOUSE TYPICAL IN COSTA RICA

Abstract. In most countries with a well-established protected agricultural production, greenhouses are built on nearly zero-slope ground, which ensures rain water drainage. Additional benefits of this practice are the avoidance of vertical temperature gradients and low temperatures inside the greenhouse. We tested the latter hypothesis in the present work, and report experimental results of the temperature and air humidity environments inside a tropical greenhouse of features typical to Costa Rica (San Jose). We examined the transient temperature and relative humidity of a greenhouse built on a hillside, in directions parallel and transversal to the slope. The greenhouse size is 33x27x2.3 m (Length x Width x Height), is a 4-span structure, has a roof window of 0.15-m height, and is located in the region “Viento Fresco de Las Brisas de Zarcero”, with a hillside slope of 60%. The temperature and relative humidity inside the greenhouse were measured with 17 sensors uniformly distributed over the ground area, logging measurements at 5-min interval over a three-month period. The data were used to validate a numerical model solved with computational fluid dynamics techniques that determined the inner thermal regimes. The statistical data showed a fairly uniform environment, with no clear temperature stratification patterns, likely caused by the localized wind current and radiation that tend to break up any onset of stratification. The maximum temperature differentials were 3.14 and 0.63° C in the directions parallel and transversal to the slope, respectively; relative humidity measurements exhibited larger gradients, with values of 11.25% and 6.04%, respectively.

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