Resumo

RUIZ-GARCIA, Agustín; LOPEZ-CRUZ, Irineo L.; ARTEAGA-RAMIREZ, Ramón  e  RAMIREZ-ARIAS, J. Armand. Natural ventilation rates of a greenhouse at central Mexico estimated by energy balance. Agrociencia [online]. 2015, vol.49, n.1, pp.87-100. ISSN 2521-9766.

The daytime air temperatures during the summer months in greenhouses of low and medium technological level in México are higher than the optimum levels of the crops, and require cooling to avoid crop stress from heat. Although natural ventilation is the principal mechanism for controlling climate in most of these greenhouses, information of their performance is scarce. The objective of the present study was to determine, by means of the energy balance method, the natural ventilation rates of a sierra type greenhouse equipped with insect screens in windows. In addition, a theoretical mathematical model of ventilation rates as a function of exterior wind velocity was adjusted to experimental data. The greenhouse is located at the experimental field of the Universidad Autónoma Chapingo, in Chapingo, México. The study was carried out with a melon crop (Cucumis melo L.) under a hydroponic system and without cultivation. The parameters of the ventilation model were estimated with the algorithm of non-linear least squares. Results showed that the ventilation rates were higher when wind velocities were higher and without cultivation. The screens installed in the windows caused a reduction in ventilation rates of 48%. The theoretical ventilation model made an acceptable prediction of the ventilation rates according to the statistical indices of determination coefficients and square root of the mean squared error.

Palavras-chave : Insect screen; model; estimation; parameter; Cucumis melo L.

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