Chayangira et al
Greener Journal of Science, Engineering and Technological Research Vol. 3 (5), pp. 166-180, May 2013.
Manuscript Number: 112912307
Effects of Different Ventilation Strategies on the Microclimate and Transpiration of a Rose Crop in a Reenhouse
Chayangira Juwawa1*, Mashonjowa Emmanuel2, and
Simba Farai Malvern1
1Department of Physics, geography and environmental science, Great Zimbabwe University.
2Department of Physics, University of Zimbabwe.
*Corresponding Author’s Email: chayangiramoyan @ yahoo. com
The study was aimed at reducing internal air temperatures of a greenhouse shelter as this is one of the main problems facing greenhouse management in warm climates such as in Zimbabwe. The water vapour balance method was used to evaluate the ventilation rate and the results were employed in calibrating and validating the ventilation sub-model of the greenhouse climate model, the GDGCM model, in a naturally ventilated three span Azrom type greenhouse in Zimbabwe. Two ventilation regimes namely: configuration with roof vents only with closed side vents and configuration with both side vents and roof vents open, were investigated. Crop transpiration was estimated using the Penman-Monteith method. The model was fitted to experimental data for ventilation rates, and the parameters for the model, the discharge and wind effect coefficient were determined using statistical analysis. The results showed that there was a good fit between measured and predicted values (R2 = 0.702 and 0.729) for the model on the two ventilation regimes. The air renewal rate was found to be influenced by the nature of ventilation regime in place. The model simulation revealed that the greenhouse has higher air renewal rates for the configuration with both roof and side vents. The greenhouse internal air temperature was reduced significantly for the latter configuration as it had lower simulated air temperatures than the former.
Keywords: ventilation rate, greenhouse, GDGCM model, air renewal, Zimbabwe.
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