Effective ventilation reduces heat stress in sows. A numerical study was carried out to investigate the effects of airspeed and direction on the convective heat transfer around a sow having different postures and body mass. The convection characteristics of a sow were analysed in a virtual wind tunnel using computational fluid dynamics (CFD) tools. The four postures of the standing, sitting, reclining and lateral lying were included. The investigated sow masses ranged from 130 kg to 340 kg. The results show that: 1) The general convective heat transfer was higher when the sow was standing or sitting postures rather than in a reclining or lateral lying posture; 2) Wind direction affects the sow convective heat transfer coefficient. The convective heat transfer coefficient of a sow was largest when it was standing or sitting with the body axis 60° to wind direction. When reclining or lateral lying sow axis at 45° to wind direction, the convective heat transfer coefficient was the largest; 3) The convective heat transfer coefficient of a single sow can be used to predict the convective heat transfer coefficient of a sow amidst rows of multiple sows; 4) Sow body mass negatively affects the convective heat transfer coefficient; 5) The convective heat transfer coefficient of the sow's trunk is relatively low compared with other parts such as the legs, head etc. Based on these results, when a sow needs to be cooled during hot conditions, an oblique airflow is recommended, and airflow speed around the sow's trunk should be increased as much as possible.

中文翻译：

---

母猪气流和对流传热的数值模拟

有效的通风可降低母猪的热应激。进行了一项数值研究，以研究空速和方向对具有不同姿势和体重的母猪周围对流传热的影响。使用计算流体动力学 (CFD) 工具在虚拟风洞中分析了母猪的对流特性。包括立、坐、卧、侧卧四种姿势。调查的母猪体重范围为 130 至 340 公斤。结果表明：1）母猪站立或坐姿时总对流传热高于斜卧或侧卧位；2) 风向影响母猪的对流传热系数。母猪体轴与风向成60°站立或坐着时，对流换热系数最大。母猪轴线与风向成45°斜卧或侧卧时，对流传热系数最大；3）单头母猪的对流换热系数可用于预测多头母猪行中一头母猪的对流换热系数；4) 母猪体重对对流传热系数有负面影响；5）母猪躯干的对流换热系数与腿、头等其他部位相比较低。基于这些结果，当母猪在炎热条件下需要冷却时，建议采用斜向气流，气流应尽可能提高围绕母猪躯干的速度。母猪轴线与风向成45°斜卧或侧卧时，对流传热系数最大；3）单头母猪的对流换热系数可用于预测多头母猪行中一头母猪的对流换热系数；4) 母猪体重对对流传热系数有负面影响；5）母猪躯干的对流换热系数与腿、头等其他部位相比较低。基于这些结果，当母猪在炎热条件下需要冷却时，建议采用斜向气流，气流应尽可能提高围绕母猪躯干的速度。母猪轴线与风向成45°斜卧或侧卧时，对流传热系数最大；3）单头母猪的对流换热系数可用于预测多头母猪行中一头母猪的对流换热系数；4) 母猪体重对对流传热系数有负面影响；5）母猪躯干的对流换热系数与腿、头等其他部位相比较低。基于这些结果，当母猪在炎热条件下需要冷却时，建议采用斜向气流，气流应尽可能提高围绕母猪躯干的速度。3）单头母猪的对流换热系数可用于预测多头母猪行中一头母猪的对流换热系数；4) 母猪体重对对流传热系数有负面影响；5）母猪躯干的对流换热系数与腿、头等其他部位相比较低。基于这些结果，当母猪在炎热条件下需要冷却时，建议采用斜向气流，气流应尽可能提高围绕母猪躯干的速度。3）单头母猪的对流换热系数可用于预测多头母猪行中一头母猪的对流换热系数；4) 母猪体重对对流传热系数有负面影响；5）母猪躯干的对流换热系数与腿、头等其他部位相比较低。基于这些结果，当母猪在炎热条件下需要冷却时，建议采用斜向气流，气流应尽可能提高围绕母猪躯干的速度。