农业工程学报
農業工程學報
농업공정학보
2014年
19期
240-249
,共10页
刘统帅%刘继军%王美芝%靳薇%陈昭辉%杨食堂
劉統帥%劉繼軍%王美芝%靳薇%陳昭輝%楊食堂
류통수%류계군%왕미지%근미%진소휘%양식당
降温%温度%射流%上置置换通风%肉牛舍%冷风机%纤维风管
降溫%溫度%射流%上置置換通風%肉牛捨%冷風機%纖維風管
강온%온도%사류%상치치환통풍%육우사%랭풍궤%섬유풍관
cooling%temperature%jets%displacement ventilation with up-fixing diffusers%beef cattle barn%cooling fan%fabric air dispersion
为了探索一种高效且运行成本低的牛舍降温方式，该试验通过设计合理的风管布置和开口，采取上置置换通风的模式对肉牛舍降温。该设计方案用计算流体力学（computational fluid dynamics，CFD）的方法验证其可行性，并通过实际测试设定风机开启和关闭的适宜时间，试验表明：处理舍系统产生的冷风大量流向牛活动区域，温湿度梯度比对照舍明显，达到了局部降温的节能目的。该系统开启后，10：00-18：00期间，处理舍牛的平均热负荷指数（heat load index，HLI）比对照舍降低7.4（P＜0.01），平均呼吸频率降低12次/min（P＜0.01），平均日增质量提高0.37 kg/d（P＜0.01），缓解了肉牛的热应激，提高了肉牛的养殖效益。处理舍由于相对封闭，故牛活动区域平均相对湿度、CO2和NH3浓度分别比对照舍高26.8%、252 mg/m3、0.54 mg/m3（P＜0.01），但牛舍环境空气质量符合相关行业标准的要求。该试验为冷风机-风管通风降温系统设计提供了一些参考参数，有利于该系统的优化，并发挥更好的降温效果。
為瞭探索一種高效且運行成本低的牛捨降溫方式，該試驗通過設計閤理的風管佈置和開口，採取上置置換通風的模式對肉牛捨降溫。該設計方案用計算流體力學（computational fluid dynamics，CFD）的方法驗證其可行性，併通過實際測試設定風機開啟和關閉的適宜時間，試驗錶明：處理捨繫統產生的冷風大量流嚮牛活動區域，溫濕度梯度比對照捨明顯，達到瞭跼部降溫的節能目的。該繫統開啟後，10：00-18：00期間，處理捨牛的平均熱負荷指數（heat load index，HLI）比對照捨降低7.4（P＜0.01），平均呼吸頻率降低12次/min（P＜0.01），平均日增質量提高0.37 kg/d（P＜0.01），緩解瞭肉牛的熱應激，提高瞭肉牛的養殖效益。處理捨由于相對封閉，故牛活動區域平均相對濕度、CO2和NH3濃度分彆比對照捨高26.8%、252 mg/m3、0.54 mg/m3（P＜0.01），但牛捨環境空氣質量符閤相關行業標準的要求。該試驗為冷風機-風管通風降溫繫統設計提供瞭一些參攷參數，有利于該繫統的優化，併髮揮更好的降溫效果。
위료탐색일충고효차운행성본저적우사강온방식，해시험통과설계합리적풍관포치화개구，채취상치치환통풍적모식대육우사강온。해설계방안용계산류체역학（computational fluid dynamics，CFD）적방법험증기가행성，병통과실제측시설정풍궤개계화관폐적괄의시간，시험표명：처리사계통산생적랭풍대량류향우활동구역，온습도제도비대조사명현，체도료국부강온적절능목적。해계통개계후，10：00-18：00기간，처리사우적평균열부하지수（heat load index，HLI）비대조사강저7.4（P＜0.01），평균호흡빈솔강저12차/min（P＜0.01），평균일증질량제고0.37 kg/d（P＜0.01），완해료육우적열응격，제고료육우적양식효익。처리사유우상대봉폐，고우활동구역평균상대습도、CO2화NH3농도분별비대조사고26.8%、252 mg/m3、0.54 mg/m3（P＜0.01），단우사배경공기질량부합상관행업표준적요구。해시험위랭풍궤-풍관통풍강온계통설계제공료일사삼고삼수，유리우해계통적우화，병발휘경호적강온효과。
In order to search for an effective cooling system that is energy saving with low running cost in beef cattle barns, this study investigated the displacement ventilation with up-fixing diffusers system to reduce heat stress of grain-fed beef cattle using an evaporative cooling air conditioner combining fabric air dispersion with rational layout and opening design. Four wet curtain cooling fans with air volume at 12 000 m3/h and 1 kW of electric power were used as the cooling source. Along the wall, four fabric ducts were connected to one cooling fan paralleled to the longitudinal wall. The diameter of the duct was 0.8 m and the bottom of the duct was 2.1 m from the floor. The duct was designed with twenty rows of big holes with 4.0 mm of diameter and 10 degrees to the vertical direction, twenty rows of small holes with 2.0 mm of diameter and 10mm from the big hole respectively. Both small and big holes directed the cooling air to the cattle bodies. As a result of the designing, the wind velocity gradient was developed at the same distance from the openings, which could avoid large jet entraining and thereby facilitated the displacement ventilation. The design of this experiment was validated with numerical simulation based on computational fluid dynamics (CFD), and the time of running and stopping the cooling system was set according to experimental measurement. Wind speed around the cattle was 0.5 m/s faster than the wind speed of feeding aisle at average. However, wind speed near the floor was less than 0.5 m/s which fits the requirement of displacement ventilation. The temperature and humidity difference of the vertical height between 2 m and 3 m from the floor in treatment barn were (1.11±0.11)℃and6.1%±0.5%respectively, while the difference in the control barn between 2 and 3 m from the floor were (0.6±0.05)℃and 3.9%±0.3%respectively. The results showed that cooling air from the fabric air dispersion mainly flowed to the area where the cattle stood, and that the temperature and humidity gradient in the treatment barn was larger than the control barn with using the ceiling fan, thus the system achieved locally cooling and reduced the energy waste. In addition, during 10:00-18:00, the average temperature and humidity of treatment barn were (31.5±0.7)℃ and 78.6%±4.4% respectively,whereas those of the control barn were (36.4±1.4)℃ and 51.8%±10.3% respectively. There was a significant difference of average temperature and humidity in both the treatment and control barns (P<0.01). Compared with the control barn, during 10:00-18:00, the heat load index (HLI) was 8.1 lower in the treatment cattle barn, the respiration rate and average daily body weight gain was significantly different by reducing 12 breaths per minute (P<0.01) and increasing 0.37 kg (P<0.01) in the treatment cattle barn, respectively, which demonstrated this design of ventilation could be effective to alleviate heat stress and improved the production performance of the beef cattle. However, the relative humidity and the concentration of CO2 and NH3 in the treatment barn was higher compared to the control barn, as a result of the shortage of air circulation outside, but the air quality in the treatment barn still could meet the requirement of relative industry standards. This study could provide parameters and suggestions for cooling fan-duct cooling system design, thus optimize and improve the cooling effect of the system.
