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Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  014061,  2001 ASAE Annual Meeting. (doi: 10.13031/2013.4347) @2001
Authors:   Edilaine Regina Pereira, Iran José Oliveira Silva, Daniella Jorge Moura
Keywords:   low tunnel , rocket press (Eruca vesicaria sativa (Mill) Thell), microclimate condition, punched plastic

The low tunnel is a type of greenhouse that is used in cultivation of species of small load like, lettuce, strawberry, sweet pepper, rocket press and cucumber. This type of greenhouse have a smaller cost of installation than the others because of its lower high. The plastic covering allows the gain of temperature during the day, making easier the growing of the plants, protecting the culture of the impact of the rain, cold wind and low temperatures. The perforation of the polyethylene film, avoid the raise of the temperatures in days with intense solar radiation, caused by the small air volume inside the tunnel. The polyethylene perforation increases the natural ventilation that dissipates the diurnal thermal heat load, avoiding the raise of the air temperature during the day that damages the cultivate development and allows that the nights temperatures inside the tunnel at higher than the external atmosphere. The purpose of this research was to determine the environmental changes that the low density polyethylene with different perforated film areas (5,10,15 and 20%) may cause on the rocket press (Eruca vesicaria sativa (Mill) Thell) development in low tunnel conditions. The climate data inside the tunnel was collected from 8:00 AM to 6:00 PM during summer time. The climate variables analyzed were the relative humidity and air temperature. The culture parameters used to compare the treatments were the final production, size of the plants, weight and number of leaves The results showed significative differences in the plant production among the treatments but hadnt significative differences between the physics characteristics of the plants. As for the microclimate generated inside the tunnels in the hottest hours of the day, it was found significative differences between the 0% perforated tunnel and the bed without tunnel. However, it wasnt found any differences among the perforated tunnels. The present research had the objective to compare the poultry building thermal efficiency using two different solar orientation: East-West and North-South. It was also verified the use of forced ventilation on the thermal behavior of the buildings, as well as the use of trees shade on the North-South roof slope. The research was done in distorted small scale models representing poultry buildings located in the experimental area of the Rural Building Department, in the Agricultural Engineering College of UNICAMP. The place was located as a latitude of 2254S and a longitude of 4705N and altitude of 674m. Five models were built such as: two in the East-West solar orientation and three in North-South. Trees were planted to provide shade in two of the North-South oriented models for reducing the solar thermal incident radiation load in the lateral walls and roof. Fans were put in each model with different orientation (one East-West and other North-South) to verify the influence of forced ventilation in both cases. Using the climatic data radiation heat load as well as the thermal balance were calculated. In order to determine the statistical difference in the several studied models, average heat production data was compared using simulated data. It was found that the building with North-South solar orientation shaded by trees and using forced ventilation presented the same thermal behavior of the ones with solar orientation East-West, where forced ventilation was used.

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