开孔方案对肉牛舍湿帘冷风机-纤维风管送风降温效果的影响

该研究通过纤维风管4种开孔方案设置，结合湿帘冷风机，满足到达1.3 m高度时，1号、2号、3号及4号风管射流风速分别为1.5、2.3、3.1、3.9 m/s；测量牛舍的环境指标和试验牛的生理指标，比较缓解热应激效果，探索较优化的开孔方案。结果表明：测定期间，4个风管区域之间温度差异不显著（P>0.05），平均比舍外低2.1℃（P<0.05）；相对湿度均低于85%。试验牛所在3号风管区域平均风速最高，为1.32 m/s；1号风管区域最低，为0.62 m/s。二氧化碳浓度3号风管区域最低，1号风管区域最高（P<0.05）。牛只呼吸频率3号风管区域最低，为42次/min，1号风管区域最高，为52次/min，肉牛呼吸频率与试验区风速显著负相关。该研究表明，湿帘冷风机-纤维风管系统可有效缓解肉牛热应激，开孔方案设置满足到达1.3 m高度时射流风速为3.1 m/s的风管效果最优。

Effect of orifice schemes on air supply and cooling performance of wet curtain fan-fiber duct in beef cattle barn

Fabric air distribution system, one of the terminal equipment in air conditioning system, can achieve uniform linear air supply and affect air jet distribution through unique orifices in the duct. It is widely used in the field of agriculture. In this study,a wet curtain cooling fan-fiber duct system was used in beef cattle barn in summer and designed to meet with jet wind speed at beef standing height (1.3 m from floor) of 1.5, 2.3, 3.1, 3.9 m/s from duct 1, duct 2, duct 3 and duct 4 respectively via different orifice schemes. The study was carried out with Simmental Crossbred Cattle in a semi-open barn. Four wet curtain cooling fans with air volume of 18000 m3/h and total pressure of 190 Pa were used as the cooling source. Four fabric ducts (Φ=0.813 m) connecting with cooling fan were mounted above the feed manager wall with a bottom height of 1.8 m from the floor. The operation time of the cooling system was from 09:00 to 19:00 based on the local environmental conditions and farm management. The zone thermal environmental parameters under the four ducts, and some physiological index of beefs were collected to evaluate the effect in alleviating heat stress and find out the best opening scheme. The results show that there were no significant differences of the average temperature and relative humidity among the four duct cooling zone (P>0.05) during the measurement period; the average temperature of the barn decreased by 2.1℃ compared with the outside (P<0.05); and the relative humidity in every duct cooling zone was less than 85%. The average wind speed was highest in duct 3 cooling zone (1.32 m/s) and was lowest in duct 1 cooling zone (0.62 m/s) (P<0.05). Meanwhile, the average carbon dioxide concentration was lowest in duct 3 cooling zone and was highest in duct 1 cooling zone (P<0.05). The beefs’ respiration rate negatively correlated with wind speed, with the lowest respiration rate in duct 3 cooling zone (42 beats/min) and highest in duct 1 cooling zone (52 beats/min). The results show that the application of a wet curtain cooling fan-fiber duct in beef cattle barn was effective in relieving cattle’s heat stress, especially duct with a designed jet wind speed of 3.1 m/s at beef standing height (1.3 m from floor) had the best effect.