农业工程学报
農業工程學報
농업공정학보
2014年
6期
139-146
,共8页
邓书辉%施正香%李保明%赵淑梅%丁涛%郑万萍
鄧書輝%施正香%李保明%趙淑梅%丁濤%鄭萬萍
산서휘%시정향%리보명%조숙매%정도%정만평
计算流体动力学%流场%模型%低屋面横向通风%奶牛舍%数值模拟
計算流體動力學%流場%模型%低屋麵橫嚮通風%奶牛捨%數值模擬
계산류체동역학%류장%모형%저옥면횡향통풍%내우사%수치모의
computational fluid dynamics%flow fields%models%low profile cross ventilated%dairy cattle barns%numerical simulation
低屋面横向通风（low profile cross ventilated，LPCV）牛舍作为中国大型奶牛场一种新的牛舍建筑形式近年来得到了广泛应用，但实际运行中存在舍内气流分布不均匀、夏季高温高湿、冬季低温高湿等环境控制技术瓶颈。为了研究LPCV牛舍空气流场的分布规律，以指导该种牛舍的改进和优化设计，该文在现场实测的基础上，采用计算流体动力学CFD（computational fluid dynamics）方法，根据现场和实验室实测值所确定的风机、湿帘等边界条件，对LPCV牛舍的气流分布进行了三维数值模拟。模拟时将牛只按与实物原型等比例引入到模型中。模拟结果表明：挡风板和颈枷下面矮墙的设置影响了舍内气流分布的均匀性。在既有牛舍挡风板设置和矮墙高度不能改变的情况下对牛舍进行了局部改造，改造后舍内气流分布得到明显改善,平均风速增加了52.8%，气流不均匀性指标降低了41.8%。模拟值与实测值的对比表明，28个测点测试值与模拟值平均相对误差的平均值为17.1%，说明现场实测与数值模拟有较好的吻合度。该研究可为中国LPCV牛舍结构优化设计和环境调控提供参考。
低屋麵橫嚮通風（low profile cross ventilated，LPCV）牛捨作為中國大型奶牛場一種新的牛捨建築形式近年來得到瞭廣汎應用，但實際運行中存在捨內氣流分佈不均勻、夏季高溫高濕、鼕季低溫高濕等環境控製技術瓶頸。為瞭研究LPCV牛捨空氣流場的分佈規律，以指導該種牛捨的改進和優化設計，該文在現場實測的基礎上，採用計算流體動力學CFD（computational fluid dynamics）方法，根據現場和實驗室實測值所確定的風機、濕簾等邊界條件，對LPCV牛捨的氣流分佈進行瞭三維數值模擬。模擬時將牛隻按與實物原型等比例引入到模型中。模擬結果錶明：擋風闆和頸枷下麵矮牆的設置影響瞭捨內氣流分佈的均勻性。在既有牛捨擋風闆設置和矮牆高度不能改變的情況下對牛捨進行瞭跼部改造，改造後捨內氣流分佈得到明顯改善,平均風速增加瞭52.8%，氣流不均勻性指標降低瞭41.8%。模擬值與實測值的對比錶明，28箇測點測試值與模擬值平均相對誤差的平均值為17.1%，說明現場實測與數值模擬有較好的吻閤度。該研究可為中國LPCV牛捨結構優化設計和環境調控提供參攷。
저옥면횡향통풍（low profile cross ventilated，LPCV）우사작위중국대형내우장일충신적우사건축형식근년래득도료엄범응용，단실제운행중존재사내기류분포불균균、하계고온고습、동계저온고습등배경공제기술병경。위료연구LPCV우사공기류장적분포규률，이지도해충우사적개진화우화설계，해문재현장실측적기출상，채용계산류체동역학CFD（computational fluid dynamics）방법，근거현장화실험실실측치소학정적풍궤、습렴등변계조건，대LPCV우사적기류분포진행료삼유수치모의。모의시장우지안여실물원형등비례인입도모형중。모의결과표명：당풍판화경가하면왜장적설치영향료사내기류분포적균균성。재기유우사당풍판설치화왜장고도불능개변적정황하대우사진행료국부개조，개조후사내기류분포득도명현개선,평균풍속증가료52.8%，기류불균균성지표강저료41.8%。모의치여실측치적대비표명，28개측점측시치여모의치평균상대오차적평균치위17.1%，설명현장실측여수치모의유교호적문합도。해연구가위중국LPCV우사결구우화설계화배경조공제공삼고。
The first low profile cross ventilated (LPCV) dairy cattle barn was built in fall 2005 in North Dakota. The barn is generally a fully enclosed facility characterized by a low roof pitch of 0.5/12 and a warehouse-type structure. It was introduced to China in 2009 and since that time several barns have been built in large dairy farms in China as a newly-developed dairy cattle barn type. The LPCV barn offers some of the advantages of natural ventilated and tunnel ventilated freestalls and allows producers to have some control over the cow’s environment during all seasons of the year. But in China there are technical bottlenecks for environmental control problems in operation, including uneven distribution of indoor airflow, high-temperature and high-humidity in summer, low-temperature and high-humidity in winter et al. The use of computational fluid dynamics (CFD) techniques to solve complex fluid problems has greatly increased in recent years. In this study, a full-scale dairy cattle house was modelled to investigate the distribution pattern of airflow in LPCV barn. The simulation of dairy cattle was considered to improve the reliability of the CFD model, as the presence of cows in barns can significantly influence air flow patterns and internal environmental conditions. The evaporative cooling pads on the air intake side of the barn were considered as porous media and the coefficients of the viscous and inertial resistances were determined by laboratory values. The performance curve of the exhaust fans on the air outtake side was measured in laboratory to establish the boundary conditions of the fans. Baffles are located over stalls in LPCV barn to increase air velocity in each freestall area. Simulation results shows that the problem of uneven flow distribution is generally exist in the barn. The wind speed differed greatly between the two sides of the baffle in the bedding area. The wind speed was significantly lower for the windward side compared with the other side. The main reason for the uneven flow distribution in the barn was the parapet below the neck rails. If there is no parapet, the average wind speed could increase by 60.6%, and the air uniformity coefficient could decrease by 68.7%. For the existing LPCV barn, keeping the baffle wall and the parapet unchanged, the air flow could be improved by the installation of a baffle on top of the neck rails of the windward of the feeding alley. The modification has a significant effect on the airflow distribution improvement, with the averaged wind velocity increased by 52.8%, the airflow uniformity coefficient decreased by 41.8%. The CFD model was validated via comparison with the field experimental results at the same locations where the sensors were installed. Comparison between simulations and measurements showed that the average relative error of the test and simulated value for the 28 test points was 17.1%, which indicates that there is a goodness of fit between field measurement and numerical simulation. And this study can provide references for the optimization design and environment regulation of LPCV dairy cattle barn in China.
