Abstract

ESPEJEL TRUJANO, Daniel  and  LOPEZ CRUZ, Irineo Lorenzo. Determination of rates of natural ventilation in a greenhouse using theoretical models and tracer gases. Rev. Mex. Cienc. Agríc [online]. 2013, vol.4, n.2, pp.185-198. ISSN 2007-0934.

In Mexico, most greenhouses use natural ventilation as the main mechanism to control the weather. Quantification of ventilation rates is difficult because these depend on the effect of fluctuating wind, resistance to airflow windows and geometry ofthe greenhouse in the field ofwind pressure on the structure. The objective of the present study was to determine the rates of natural ventilation in a greenhouse under three ventilation configurations: side windows, zenith and side-zenith, by the dynamic method of tracer gases. Measurements were compared against predictions of theoretical models of natural ventilation and analyzed the effect of wind speed on ventilation rates. The greenhouse is located at the experimental field of San Ignacio in the University of Chapingo, Chapingo, Mexico. The experiment was conducted in 2010 and the greenhouse was free of crops. The tracer gas used was carbon dioxide. To estimate the parameters the non-linear least squares algorithm was used. The results showed that ventilation rates are dependent on the wind speed and configuration ofthe existing windows. The higher ventilation rates were observed when both side and zenith windows were open. Theoretical models acceptably predicted ventilation rates, taking into account the values of the statistical coefficients of determination and mean square error, as the behavior ofthe 1:1 line between predictions and measurements.

Keywords : greenhouse ventilation rates; tracer gases; concentration decay method; ventilation model.