低屋面横向通风牛舍空气流场CFD模拟
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摘要
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。
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.
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.
引文
[1]Harner J P,Smith J F.Low-profile cross-ventilated freestall facilities–A 2 year summary[C]//Proceeding of the 2008 High Plains Dairy Conference.Albuquerque:High Plains Dairy Conference,2008:65-78.
[2]Harner J P,Smith J F,Millner R.Characteristics of low-profile cross-ventilated freestalls[C]//Proceeding of dairy research 2006.Kansas:Kansas State University.Agricultural Experiment Station and Cooperative Extension Service,2006:49-51.
[3]Harner J P,Smith J F,de Haro Marti M,et al.Comprehensive evaluation of a low-profile cross-ventilated freestall barn[C]//Proceeding of the 7th Western Dairy Management Conference.Reno:Western Dairy Management Conference,2007:127-147.
[4]Smith J F,Harner J P,Bradford B J,et al.Opportunities with low profile cross ventilated freestall facilities[C]//Proceeding of the Dairy Housing of the Future-Opportunities with Low Profile Cross Ventilated Housing Conference.Sioux Falls:Kansas State University Research and Extension,2008:1-20.
[5]Dhuyvetter K C,Harner J P,Smith J F,et al.Economic considerations of low profile cross ventilated barns[C]//Proceeding of the Dairy Housing of the Future-Opportunities with Low Profile Cross Ventilated Housing Conference.Sioux Falls:Kansas State University Research and Extension,2008:89-100.
[6]Harner J P,Smith J F,Bradford B J,et al.In the thermoneutral zone:Potential benefits of LPCV buildings[C]//Proceeding of the Western Dairy Management Conference.Reno:Western Dairy Management Conference,2009:27-41.
[7]Lobeck K M,Endres M I,Shane E M,et al.Animal welfare in cross-ventilated,compost-bedded pack,and nat-urally ventilated dairy barns in the upper Midwest[J].Journal of Dairy science,2011,94(11):5469-5479.
[8]颜志辉,施正香,王朝元,等.大跨度横向机械通风奶牛舍环境状况的分析与思考[J].中国畜牧杂志,2012,48(16):43-46.
[9]曹士明,马满友,王永红.大型奶牛养殖场粪污处理系统与泌乳牛舍饲养环境控制新技术的应用[J].中国奶牛,2011(17):46-49.
[10]李守忠.低屋面横向通风牛舍(LPCV)[C]//中国奶业协会年会论文集2009(上册).杭州:2009:366-368.
[11]蒋国振,胡耀华,刘玉凤,等.基于CFD的下沉式日光温室保湿性能分析[J].农业工程学报,2011,27(12):275-281.Jiang Guozhen,Hu Yaohua,Liu Yufeng,et al.Analysis on insulation performance of sunken solar greenhouse based on CFD[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2011,27(12):275-281.(in Chinese with English abstract)
[12]张起勋,于海业,张忠元,等.利用CFD模型研究日光温室内的空气流动[J].农业工程学报,2012,28(16):166-171.Zhang Qixun,Yu Haiye,Zhang Zhongyuan,et al.Airflow simulation in solar greenhouse using CFD model[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2012,28(16):166-171.(in Chinese with English abstract)
[13]Wang Rui,Xu Hui,Ma Jian,et al.CFD analysis of airflow distribution in greenhouse with pad and fan coolong system[J].Transactons of the CSAE,2011,27(6):250-255.王蕊,须晖,马健,等.基于流体力学的湿帘风机温室内气流运动的模拟分析(英文)[J].农业工程学报,2011(6):250-255.(in English with Chinese abstract)
[14]Kim K S,Yoon J Y,Kwon H J,et al.3-D CFD analysis of relative humidity distribution in greenhouse with a fog cooling system and refrigerative dehumidifiers[J].Biosystems Engineering,2008,100(2):245-255.
[15]佟国红,张国强,Morsing S,等.猪舍内气流变化的模拟研究[J].沈阳农业大学学报,2007,38(3):379-382.Tong Guohong,Zhang Guoqiang,Morsing S,et al.Airflow simulation in a scale model of the swine building[J].Journal of Shengyang Agricultural University,2007,38(3):379-382.(in Chinese with English abstract)
[16]李文良,施正香,王朝元.密闭式平养鸡舍纵向通风的数值模拟[J].中国农业大学学报,2007,12(6):80-84.Li Wenliang,Shi Zhengxiang,Wang Chaoyuan.Numerical simulation of tunnel ventilation system of plane-raising enclosed henhouse[J].Journal of China Agricultural University,2007,12(6):80-84.(in Chinese with English abstract)
[17]王小超,陈昭辉,王美芝,等.冬季猪舍热回收换气系统供暖的数值模拟[J].农业工程学报,2011,27(12):227-233.Wang Xiaochao,Chen Zhaohui,Wang Meizhi,et al.Numerical simulation of heat supply for heat recovery ventilation system of piggery in winter[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2011,27(12):227-233.(in Chinese with English abstract)
[18]Bartzanas T,Kittas C,Sapounas A A,et al.Analysis of airflow through experimental rural buildings:sensitivity to turbulence models[J].Biosystems Engineering,2007,97(2):229-239.
[19]Mostafa E,Lee I B,Song S H,et al.Computational fluid dynamics simulation of air temperature destribution inside broiler building fitted with duct ventilation system[J].Biosystems Engineering,2012,112(4):293-303.
[20]贺城,牛智有,齐德生.猪舍温度场和气流场的CFD模拟比较分析[J].湖北农业科学,2010,49(1):134-136.He Cheng,Niu Zhiyou,Qi Desheng.CFD simulation and comparative analysis about air temperature and airflow in the piggery[J].Hubei Agricultural Sciences,2010,49(1):134-136.(in Chinese with English abstract)
[21]Bjerg B,Zhang G Q,Kai P.Porous media as boundary condition for air inlet,slatted floor and animal occupied zone in numerical simulation of airflow in a pig unit[C]//Crete:Agricultural and biosystems engineering for a sustainable world-International Conference on Agricultural Engineering,2008:23-25.
[22]Gebremedhin K G,Wu B.Simulation of flow field of a ventilated and occupied animal space with different inlet and outlet conditions[J].Journal of Thermal Biology,2005,30(5):343-353.
[23]Wu B,Gebremedhin K G.CFD development and simulation of flow fields in ventilated spaces with multiple occupants[J].Transactons of the ASAE,44(6):1839-1850.
[24]Seo I H,Lee I B,Moon O K,et al.Modelling of internal environmental conditions in a full-scale commercial pig house containing animals[J].Biosystems Engineering,2012,111(1):91-106.
[25]王福军.计算流体动力学分析-CFD软件原理与应用[M].北京:清华大学出版社,2004:7-11.
[26]田海林,李曦,孙梦瑶,等.常用湿帘产品的技术性能测试[J].农机化研究,2013,35(4):148-151.Tian Hailin,Li Xi,Sun Mengyao,et al.Technical Performance Testing of Commonly Used Specifications Wet Pad[J].Journal of Agricultural Mechanization Research,2013,35(4):148-151.(in Chinese with English abstract).
[27]李鹏飞,徐敏义,王飞飞.精通CFD工程仿真与案例实战[M].北京:人民邮电出版社,2011:182-186.
[28]邓书辉,施正香,范淋佳,等.基于CFD的开放式牛舍扰流风机安装参数优化[J].农业机械学报,2013,44(12):269-274.Deng Shuhui,Shi Zhengxiang,Fan Linjia,et al.Optimization of installation parameters of mixing fans in open dairy cow house based on CFD[J].Transactions of the Chinese Society for Agricultural Machinery,2013,44(12):269-274.(in Chinese with English abstract).
[29]陈树林,贾先斌.奶牛舍机械通风的模型试验与研究[J].北京农业机械化学院学报,1984(1):41-51.Chen Shulin,Jia Xianbin.Model experiment on ventilation in dairy barn[J].Transactions of Beijing Agricultural Mechanization College,1984(1):41-51.(in Chinese with English abstract)
[30]赵荣义,范存养,薛殿华,等.空气调节:第4版[M].北京:中国建筑工业出版社,2009:182-184.
[31]李先庭,赵彬,邵晓亮,等.建筑通风[M].北京:机械工业出版社,2011:134-152.
[2]Harner J P,Smith J F,Millner R.Characteristics of low-profile cross-ventilated freestalls[C]//Proceeding of dairy research 2006.Kansas:Kansas State University.Agricultural Experiment Station and Cooperative Extension Service,2006:49-51.
[3]Harner J P,Smith J F,de Haro Marti M,et al.Comprehensive evaluation of a low-profile cross-ventilated freestall barn[C]//Proceeding of the 7th Western Dairy Management Conference.Reno:Western Dairy Management Conference,2007:127-147.
[4]Smith J F,Harner J P,Bradford B J,et al.Opportunities with low profile cross ventilated freestall facilities[C]//Proceeding of the Dairy Housing of the Future-Opportunities with Low Profile Cross Ventilated Housing Conference.Sioux Falls:Kansas State University Research and Extension,2008:1-20.
[5]Dhuyvetter K C,Harner J P,Smith J F,et al.Economic considerations of low profile cross ventilated barns[C]//Proceeding of the Dairy Housing of the Future-Opportunities with Low Profile Cross Ventilated Housing Conference.Sioux Falls:Kansas State University Research and Extension,2008:89-100.
[6]Harner J P,Smith J F,Bradford B J,et al.In the thermoneutral zone:Potential benefits of LPCV buildings[C]//Proceeding of the Western Dairy Management Conference.Reno:Western Dairy Management Conference,2009:27-41.
[7]Lobeck K M,Endres M I,Shane E M,et al.Animal welfare in cross-ventilated,compost-bedded pack,and nat-urally ventilated dairy barns in the upper Midwest[J].Journal of Dairy science,2011,94(11):5469-5479.
[8]颜志辉,施正香,王朝元,等.大跨度横向机械通风奶牛舍环境状况的分析与思考[J].中国畜牧杂志,2012,48(16):43-46.
[9]曹士明,马满友,王永红.大型奶牛养殖场粪污处理系统与泌乳牛舍饲养环境控制新技术的应用[J].中国奶牛,2011(17):46-49.
[10]李守忠.低屋面横向通风牛舍(LPCV)[C]//中国奶业协会年会论文集2009(上册).杭州:2009:366-368.
[11]蒋国振,胡耀华,刘玉凤,等.基于CFD的下沉式日光温室保湿性能分析[J].农业工程学报,2011,27(12):275-281.Jiang Guozhen,Hu Yaohua,Liu Yufeng,et al.Analysis on insulation performance of sunken solar greenhouse based on CFD[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2011,27(12):275-281.(in Chinese with English abstract)
[12]张起勋,于海业,张忠元,等.利用CFD模型研究日光温室内的空气流动[J].农业工程学报,2012,28(16):166-171.Zhang Qixun,Yu Haiye,Zhang Zhongyuan,et al.Airflow simulation in solar greenhouse using CFD model[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2012,28(16):166-171.(in Chinese with English abstract)
[13]Wang Rui,Xu Hui,Ma Jian,et al.CFD analysis of airflow distribution in greenhouse with pad and fan coolong system[J].Transactons of the CSAE,2011,27(6):250-255.王蕊,须晖,马健,等.基于流体力学的湿帘风机温室内气流运动的模拟分析(英文)[J].农业工程学报,2011(6):250-255.(in English with Chinese abstract)
[14]Kim K S,Yoon J Y,Kwon H J,et al.3-D CFD analysis of relative humidity distribution in greenhouse with a fog cooling system and refrigerative dehumidifiers[J].Biosystems Engineering,2008,100(2):245-255.
[15]佟国红,张国强,Morsing S,等.猪舍内气流变化的模拟研究[J].沈阳农业大学学报,2007,38(3):379-382.Tong Guohong,Zhang Guoqiang,Morsing S,et al.Airflow simulation in a scale model of the swine building[J].Journal of Shengyang Agricultural University,2007,38(3):379-382.(in Chinese with English abstract)
[16]李文良,施正香,王朝元.密闭式平养鸡舍纵向通风的数值模拟[J].中国农业大学学报,2007,12(6):80-84.Li Wenliang,Shi Zhengxiang,Wang Chaoyuan.Numerical simulation of tunnel ventilation system of plane-raising enclosed henhouse[J].Journal of China Agricultural University,2007,12(6):80-84.(in Chinese with English abstract)
[17]王小超,陈昭辉,王美芝,等.冬季猪舍热回收换气系统供暖的数值模拟[J].农业工程学报,2011,27(12):227-233.Wang Xiaochao,Chen Zhaohui,Wang Meizhi,et al.Numerical simulation of heat supply for heat recovery ventilation system of piggery in winter[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2011,27(12):227-233.(in Chinese with English abstract)
[18]Bartzanas T,Kittas C,Sapounas A A,et al.Analysis of airflow through experimental rural buildings:sensitivity to turbulence models[J].Biosystems Engineering,2007,97(2):229-239.
[19]Mostafa E,Lee I B,Song S H,et al.Computational fluid dynamics simulation of air temperature destribution inside broiler building fitted with duct ventilation system[J].Biosystems Engineering,2012,112(4):293-303.
[20]贺城,牛智有,齐德生.猪舍温度场和气流场的CFD模拟比较分析[J].湖北农业科学,2010,49(1):134-136.He Cheng,Niu Zhiyou,Qi Desheng.CFD simulation and comparative analysis about air temperature and airflow in the piggery[J].Hubei Agricultural Sciences,2010,49(1):134-136.(in Chinese with English abstract)
[21]Bjerg B,Zhang G Q,Kai P.Porous media as boundary condition for air inlet,slatted floor and animal occupied zone in numerical simulation of airflow in a pig unit[C]//Crete:Agricultural and biosystems engineering for a sustainable world-International Conference on Agricultural Engineering,2008:23-25.
[22]Gebremedhin K G,Wu B.Simulation of flow field of a ventilated and occupied animal space with different inlet and outlet conditions[J].Journal of Thermal Biology,2005,30(5):343-353.
[23]Wu B,Gebremedhin K G.CFD development and simulation of flow fields in ventilated spaces with multiple occupants[J].Transactons of the ASAE,44(6):1839-1850.
[24]Seo I H,Lee I B,Moon O K,et al.Modelling of internal environmental conditions in a full-scale commercial pig house containing animals[J].Biosystems Engineering,2012,111(1):91-106.
[25]王福军.计算流体动力学分析-CFD软件原理与应用[M].北京:清华大学出版社,2004:7-11.
[26]田海林,李曦,孙梦瑶,等.常用湿帘产品的技术性能测试[J].农机化研究,2013,35(4):148-151.Tian Hailin,Li Xi,Sun Mengyao,et al.Technical Performance Testing of Commonly Used Specifications Wet Pad[J].Journal of Agricultural Mechanization Research,2013,35(4):148-151.(in Chinese with English abstract).
[27]李鹏飞,徐敏义,王飞飞.精通CFD工程仿真与案例实战[M].北京:人民邮电出版社,2011:182-186.
[28]邓书辉,施正香,范淋佳,等.基于CFD的开放式牛舍扰流风机安装参数优化[J].农业机械学报,2013,44(12):269-274.Deng Shuhui,Shi Zhengxiang,Fan Linjia,et al.Optimization of installation parameters of mixing fans in open dairy cow house based on CFD[J].Transactions of the Chinese Society for Agricultural Machinery,2013,44(12):269-274.(in Chinese with English abstract).
[29]陈树林,贾先斌.奶牛舍机械通风的模型试验与研究[J].北京农业机械化学院学报,1984(1):41-51.Chen Shulin,Jia Xianbin.Model experiment on ventilation in dairy barn[J].Transactions of Beijing Agricultural Mechanization College,1984(1):41-51.(in Chinese with English abstract)
[30]赵荣义,范存养,薛殿华,等.空气调节:第4版[M].北京:中国建筑工业出版社,2009:182-184.
[31]李先庭,赵彬,邵晓亮,等.建筑通风[M].北京:机械工业出版社,2011:134-152.