鸡体鸡笼阻挡对密闭鸡舍气流运动影响的数值研究

在建立密闭式鸡舍机械通风系统气流运动方程的基础上,推导了由流函数和势函数表示的气流运动控制方程。根据能量变分原理,导出了平面等参可变节点的统一有限元模型。重点讨论了流函数形式下的多连通域(即鸡舍内存在阻挡物)方程的数值分析法。提出了采用流场叠加法求解时的两种内边界条件确定方法:①切向循环速度为零条件:在任一封闭内边界上切向循环速度为零;②能量最小条件:真实内边界条件使整体流场的能量最小。通过上述两种条件建立了原方程的补充代数方程,使问题得到了圆满解决。运用数值模拟,比较了横向通风与纵向通风系统在舍内气流分布型式上的特点。结果表明,在纵向通风形式下,鸡舍内的气流分布非常均匀,鸡体鸡笼等障碍物对空气运动的阻挡作用不十分明显。相反,横向通风系统的气流分布极不均匀,尤其下部鸡笼周围的气流速度大大降低。     

鸡舍纵向通风系统设计与应用中的几个问题

针对当前我国在原密闭式鸡舍的横向通风与开放式或半开放式鸡舍的自然通风方式改造成纵向通风过程中存在的一些问题,着重分析讨论了鸡舍纵向通风系统的通风换气量与舍内风速取值,进气口面积与位置的确定,风机的选型及其不同季节的运行管理等问题。为今后我国不同类型鸡舍的纵向通风系统的设计与应用提供参考。     

地下汽车库通风排烟设计中应注意的几个问题

本文论述了在执行GB50067-91《汽车库修车库、停车库设计防火规范》的基础上,设计地下车库排风排烟、进风系统时应注意的几个问题。     

Oral Lesions Associated with Orotracheal Administered Mechanical Ventilation in Critically III Dogs

The incidence and clinical progression of oral lesions in a cohort of critically ill patients administered mechanical ventilation via orotracheal intubation were observed prospectively in the Intensive Care Unit (ICU) of the University of California, Davis Veterinary Medical Teaching Hospital. Oral cavities of these patients were examined within 24 hours of being placed on the ventilator and at least daily thereafter during ventilator therapy. As part of the study protocol, any lesion noted was treated. Twenty-one critically ill canine patients (median age of 7 yrs; range <1 to 19 yrs) were observed from 1 January 1995 through 31 August 1995. Over ninety percent (90.5%) of the observed patients developed oral lesions subsequent to being mechanically ventilated. Erosive and ulcerative mucosal lesions were the most frequently observed (15/43) with the tongue being the most frequently involved oral structure. Most of the observed soft tissue oral lesions appeared secondary to persistently applied pressure from teeth, mouth gags, endotracheal tubes, and other monitoring devices. Efforts taken to prevent persistently applied trauma, such as periodic positional changes of equipment and padding of susceptible structures, apeared effective in preventing oral lesions. There were indications of gastric reflux in 6 patients (28.6%), as evidenced by secretions in the oral cavity with a pH of <6 and containing digested blood. Ulcerative lesions in the subset of patients with gastric reflux seemed to worsen in severity with exposure to the low pH secretions. Over the course of the study, the ICU nursing staff developed an effective protocol for the care of the oral cavity: treating mucosal erosions and ulcers topically8 with a dilute chlorhexidine solution (0.05%), removing oral secretions via suction as needed, and padding persistently traumatized tissues with glycerin moistened gauze. Oral lesions in orotrachealy intubated and mechanically ventilated patients are predictable, preventable, and treatable. Most lesions are pressure induced, associated with monitoring/therapeutic equipment, and appear to be preventable with appropriate nursing protocls. Most observed oral lesions clinically improved with routine, periodic dilute chlorhexidine rinses and relief of applied pressure.     

Airway management under general anaesthesia in pigs using the LMA-ProSeal: a pilot study

OBJECTIVE: Evaluation of the LMA-ProSeal for positive pressure ventilation (PPV) in the pig. STUDY DESIGN: Prospective observational study. ANIMALS: Twelve German country pigs, weighing 25-62 kg. METHOD: Lungs of pigs were mechanically ventilated under general anaesthesia using the LMA-ProSeal. The ease of insertion, number of attempts and total time until placement of the LMA-ProSeal and gastric tube were recorded. Bronchoscopy was performed to determine the position of the LMA-ProSeal and to detect signs of aspiration. Ventilation variables and the leak airway pressure (P(leak)) were measured. An arterial blood gas sample was taken to determine the adequacy of ventilation. RESULTS: The airway was secured in all pigs within 39 +/- 19 seconds (27-51). Different sizes of LMA-ProSeal were used; up to 30 kg: size 3, up to 43 kg: size 4; and above 43 kg: size 5. In all but one animal the P-LMA and gastric tube were inserted at the first attempt. In nine animals gastric fluid was drained through the gastric tube. There was no evidence of aspiration in any animal. The mean [+/-SD (95%CI)]P(leak) was 28.8 +/- 7.5 cm H(2)O (24.06-33.60) and normal ventilation was achieved in all animals. CONCLUSIONS: The results of this study indicate that the airway of pigs weighing 25-62 kg can be secured safely and reliably with the sizes 3, 4 and 5 LMA-ProSeal. CLINICAL RELEVANCE: Endotracheal intubation in pigs can be difficult so there is a risk of hypoxemia in the apnoeic animal. With the LMA-ProSeal the airway can be secured rapidly, safely and reliably. Use of the Standard-LMA under PPV can be associated with gas leakage into the stomach and the subsequent risk of gastric distension and regurgitation. Both the ability to drain the stomach and the high P(leak) of the LMA-ProSeal could contribute to improved protection against aspiration under PPV.     

水帘过滤负压抽风对兔舍小气候和家兔的影响

[目的]探讨水帘过滤负压纵向通风调节室内小气候的可行性,为标准化兔舍设计提供依据。[方法]选用水帘过滤负压抽风兔舍和室内放置轴流通风机兔舍各一栋,在开启有关设备时测定室内温度、湿度、氨气浓度、空气流速的变化,统计对比母兔的繁殖仔兔数、死亡数、投入产出指标。[结果]试验兔舍与对照兔舍的温度差异显著(P<0.05),氨气浓度差异极显著(P<0.01),母兔的繁殖率明显提高,死亡数、单位生产成本明显降低。[结论]水帘降温纵向抽风可以有效控制室内小气候,是一种能兼顾降温与通风且单位生产成本较低的方法,值得在南方兔舍设计中推广。     

A Mathematical Model of Solar Energy Storage Ventilation System

A mathematical model of solar energy storage ventilation system was built in order to calculate the heat storage during daytime and the ventilation rate during nighttime. Based on meteorological parameters of Kunming in China, phase change materials(PCM) were used at the temperature of 38 ℃, 44 ℃, 50 ℃ and 63 ℃ respectively to search the relationship between ventilation volume and the angle of chimney. The modeling calculation results show that for different phase change materials, and in any angle, the trend of heat accumulation is consistent, namely heat accumulation is smaller with a higher phase change temperature. Considering both the average hourly ventilation volume and the duration, the best angle of this system should be 45°, and the best phase change material should be 38 ℃ myristoyl.     

夏季采用湿帘通风系统的密闭式肉种鸡舍温热环境因子的变化

选择华南农业大学增城正大肉鸡发展中心的肉种鸡舍为研究对象,在夏季分别对该鸡舍的气温、气湿、风速等温热环境因子进行测定,用以评价该鸡舍采用的湿帘通风系统对鸡舍内温热环境因子的调节效果。结果表明,夏季采用湿帘通风系统的鸡舍平均舍温比舍外气温低3~4℃,相对湿度保持在80%左右;夏季采用湿帘通风系统可以有效地降低舍温,主要表现为前端降温效果明显,后部降温效果有所下降;中间比两侧的降温效果好。表明夏季采用湿帘通风系统对种鸡舍内的温热环境控制较好。     

湛江地区肉牛棚舍环境评价

为了解热带地区双坡式棚舍散栏饲养模式下的环境特征,在湛江测定了肉牛舍的温度、湿度、气流、PM10等指标。结果表明:棚舍内外温湿度几乎相同,换气量超过了最大换气量,PM10优于卫生标准,温湿指数范围为78～85,处于热应激状态。考虑了气流影响的体感温度范围为25～30.5℃,晴天的14:00和19:00,风速为0.95～1.30 m/s,气流显著地减少了高温的影响。棚顶隔热能力差,晴天棚顶内外表面温差不足1℃,棚顶内表面最高可达60.8℃,此时的舍内气温仅为33.4℃,棚舍自然换气调节是环境控制的主体。