科研之友
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摘要
Maintaining proper environment in hen house by mechanical ventilation is essential for the production. In order to fully mix the cold inlet air in winter with room air, the free space beneath ceiling of hen house is normally large. However, in summer, such a design is not optimal for tunnel ventilation that air is drawn into one end of the house and exhausted at the other end, i.e., a large portion of the ventilation air would pass through the free space under ceiling instead of caged-hen occupied zone (CZ), which leads to reduced air speed in CZ as well as wind chill effect. To solve this problem, application of deflectors beneath the ceiling was investigated by computational fluid dynamics (CFD) simulations. To assess the effect of deflectors, the indoor air speed and distribution with deflectors were compared to those without deflectors. The effects of heights (0.4 m, 0.55 m, 0.7 m, 0.85 m and 1 m) and intervals (6 m, 9 m, 12 m, 15 m and 18 m) of deflectors on air speed and distribution in CZ were analyzed. The CZ was modelled as porous media in simulations to reduce mesh numbers. The resistance coefficients in x, y and z directions were derived by pressure drop through CZ in a virtual wind tunnel with one cage of birds. The hen house model was validated by a set of field measurement data. A reasonable agreement was found between measured and simulated values (the relative difference is within 10%). The investigation showed that the deflectors could significantly direct airflow downwards and increase the air speed in CZ and aisle zone by 0.66 m s(-1) and 0.91 m s(-1), respectively, than those without deflectors, when deflectors were 1 m height with interval of 6 m. The average air speed changes in CZ were linearly related to the height and interval of deflectors. Along the length direction of cage, the variation trends of air speed were almost identical under different heights of deflectors, while under varied intervals, the air speed variation trends had significant difference. The uniformity of airflow distribution in CZ, which was defined as ratio of standard deviation of air speed to the mean, was increased by application of the deflectors. The uniformity was positively related to height and negatively related to the interval of deflectors.
- 出版日期2018-8
- 单位中国农业大学
