Using CFD to assess the influence of ceiling deflector design on airflow distribution in hen house with tunnel ventilation
Using CFD to assess the influence of ceiling deflector design on airflow distribution in hen house with tunnel ventilation
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DOI：
10.1016/j.compag.2018.05.029
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发表时间：
2018-08-01
影响因子：
8.3
通讯作者：
Li, Baoming
中科院分区：
文献类型：
--
作者：
Cheng, Qiongyi;Li, Hao;Li, Baoming
通过机械通风维持鸡舍内适当的环境对于生产至关重要。为了使冬季冷进风与室内空气充分混合，鸡舍天花板下方的自由空间通常较大。然而，在夏季，这种设计对于隧道通风来说并不是最佳的，空气从鸡舍的一端吸入，另一端排出，即大部分通风空气将通过天花板下的自由空间而不是笼养鸡占据区（CZ），这会导致CZ内风速降低并产生风寒效应。为了解决这个问题，通过计算流体动力学 (CFD) 模拟研究了天花板下方导流板的应用。为了评估导流板的效果，将有导流板的室内空气速度和分布与没有导流板的室内空气速度和分布进行了比较。分析了导流板高度（0.4 m、0.55 m、0.7 m、0.85 m、1 m）和间距（6 m、9 m、12 m、15 m、18 m）对CZ内风速和分布的影响。在模拟中，CZ 被建模为多孔介质，以减少网格数量。 x、y 和 z 方向的阻力系数是通过在装有一笼鸟的虚拟风洞中通过 CZ 的压降得出的。鸡舍模型通过一组现场测量数据进行了验证。测量值和模拟值之间存在合理的一致性（相对差异在 10% 以内）。调查结果表明，当导流板高度为1 m、间距为6 m时，导流板能够显着引导气流向下，使CZ和过道区域的风速分别比不加导流板的情况提高0.66 m s(-1)和0.91 m s(-1)。 CZ 中的平均风速变化与导流板的高度和间隔呈线性关系。沿笼体长度方向，不同导流板高度下，风速变化趋势基本一致，而不同间距下，风速变化趋势存在显着差异。 CZ 中气流分布的均匀性（定义为风速标准偏差与平均值的比率）通过导流板的应用而得到提高。均匀度与高度正相关，与导流板间隔负相关。
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.