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

Abstract: 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.