温室自然通风研究

与强制降温相比,温室自然通风是一种较经济的降温方式。本文对比分析了自然通风的几种研究方法,发现示踪气体测量技术和通过数理模型计算通风率的方法是研究自然通风原理和效果的比较直接的方法,它们为能量守恒环境参数预测模型研究奠定了基础。目前借助自然通风率计算公式,应用能量守恒方法研究自然通风应用比较广泛。虽然前人对自然通风已经做了非常深入的研究,但尚未涉及应用预测模型,决策采用天窗通风还是天窗、侧窗同时通风;以及不同通风面积的降温能力,并且还没有将自然通风模型应用到温室自动控制系统中。因此,建立温室自然通风环境预测模型,通过精确的试验,确定模型参数,并将模型应用于指导温室环境控制,具有积极的意义。     

Thermally Induced Ventilation of Livestock Transporters

Livestock require ventilation during transport to ensure acceptable air temperatures, humidities and contaminant levels. Provision of ventilation in pig, sheep and cattle vehicles is usually through apertures positioned along the sides. Air exchange through these apertures occurs by forced ventilation, from vehicle motion or wind, or by thermally induced ventilation, generated by heat from the animals causing internal to external air temperature differences. Thermally induced ventilation is always present, but forced ventilation may be intermittent; particularly for a stationary vehicle on an enclosed roll-on roll-off ferry deck which prompted this study. Thus, to ensure adequate ventilation at all times, design calculations should be based on thermally induced ventilation.A model is presented which takes into account thermally induced ventilation through slot openings, heat transfer through the structure of the vehicle and heat, moisture and carbon dioxide output of the animals. Predictions of vehicle internal air temperature show this to be very insensitive to vehicle characteristics, species, heat output and stocking density. This arises because the ventilation is caused by the animal heat increasing the vehicle internal air temperature and consequently increasing the internal to external air temperature difference. For a given vent area, reducing stocking density, and thus animal heat, reduces the ventilation rate resulting in an internal air temperature which is largely self compensating. Comparison of predicted results with measurements made on a ferry voyage show agreement of vehicle internal air temperature to better than ±1°C and relative humidity to +6%.     

Emission of Nitrous Oxide and other Trace Gases during Composting of Grass and Green Waste

The emission of trace gases during composting of green waste from land maintenance (fresh cuttings of mixed herbage from fallow land) were studied. Concentrations of nitrous oxide and other trace gases were measured in experimental compost heaps by means of an infrared gas analyser and a high-resolution FT-IR spectrometer. It was verified that the maintenance of aerobic conditions is essential to keep emissions of methane and nitrous oxide at a low rate. Estimates made using a simple air transport model, indicated that the emission of nitrous oxide during composting of green waste from land maintenance was about 0·5% of the total nitrogen content of the initial material. Carbon monoxide was also detected in the compost air and its emission during biodegradation corresponded to about 0·04% of the initial carbon content of green waste.For a detailed evaluation of the findings during field experiments, laboratory apparatus for measuring the composition of compost air was developed. The measurements were performed at a temperature of 35°C and at different ventilation rates. Moistened plant material (dry cuttings of mixed herbage from fallow land) amended with lime saltpetre was used as compost substrate. At a ventilation rate of 100 cm³/min of air per kg of substrate, the maximum emission rate of nitrous oxide was 2·2 mg/h per kg of substrate. The maximum emission rate increased to 13·3 mg/h kg, when the ventilation rate was lowered to 20 cm³/min kg. The emission rate of carbon monoxide was about 40 μg/h per kg of substrate at the low ventilation rate and rose above 200μg/h kg at the higher ventilation rate.     

Greenhouse Ventilation Rate: Theory and Measurement with Tracer Gas Techniques

Leakage and ventilation rates were measured in a four span glasshouse at Silsoe Research Institute. Two tracer gas techniques were used, a decay rate method with different positions of the leeward ventilator (0, 10 and 20% of the maximum opening) and a continuous injection method with the leeward ventilators open 10%. The influences of wind speed, wind direction and temperature difference between inside and outside were analysed for each ventilator position. It was found that wind speed had a strong influence on leakage and ventilation rates. Some influence of wind direction occurred with northeast and southeast winds but no significant conclusions can be drawn because of insufficient data. Temperature difference affected ventilation rates under low wind speeds. For each ventilator position, the air exchange rate was linearly related to wind speed. A dimensionless function was calculated to express the ventilation flux per unit ventilator area and unit wind speed as a function of the angle of ventilator opening. With a 10% opening, the results obtained with the decay and continuous methods were compared and showed good agreement for wind speeds greater than 1 m/s.The results for 10 and 20% ventilator openings obtained by using the decay method were compared with those obtained by applying the theory of convection, using pressure differences generated by wind forces and temperature differences. It was found that the combined effect of wind and temperature difference gave satisfactory predictions of ventilation rates. Also, the values obtained by measurement and prediction based on pressure difference were in close agreement, with a global wind effect coefficient similar to that found in the literature.     

畜禽舍环境控制及防疫系统试验

为有效控制畜禽舍环境质量,净化空气,该文介绍了一种畜禽舍环境控制的技术措施,利用空气电净化防疫防病技术,构建一套防疫系统。试验结果表明,封闭式保育猪舍的除尘率在70%,细菌率维持在50%。利用空气电净化防疫措施,能够有效削减畜禽舍载畜载禽环境中的粉尘和空气微生物,可有效控制畜禽舍环境质量,净化空气,达到防疫的目的,是一种应用价值很高的有害微生物消灭方法。      

食用菌菇房环境CFD模拟及送风管布置方案研究

食用菌栽培菇房生产规模化和大型化的发展,对通风部件和控制系统提出更高的要求.为此,以草菇栽培菇房为研究对象,进行环境测量试验,建立菇房CFD模型,进行CFD非稳态模拟,分析其内部环境分布情况,并讨论了通风部件参数对菇房内流场分布的影响.结果显示:模拟值与试验数据的最大绝对误差为0.3℃,吻合性较好;菇房的通风方式为紊流...     

冬季猪舍粪便贮存过程中CH4排放特征试验

利用丹麦猪舍和液态猪粪便进行了CH4气体排放测试,比较了3种粪坑内粪便高度（0.15、0.40、0.65m）、4种通风量（211、650、1852、3088m3/h）、粪坑内有无挡板情况下冬季猪舍粪便贮存过程中CH4排放通量。测试结果表明：粪便高度、粪便温度和通风量可以用来解释大部分的CH4排放通量变化差异;对于使用渗透性天花板进气和负压通风排气系统,4种通风量之间CH4排放通量差异不显著,但由于通风量的增加同时会降低舍内与粪坑内空气温度和粪便温度,因此要综合考虑通风量和温度对气体排放通量的影响;液态猪粪便中CH4排放通量随着粪坑内粪便高度的降低而减少;设置粪坑挡板对粪坑内CH4排放没有影响;敏感性分析表明CH4排放通量相对于粪便温度、粪便高度和通风量的敏感性依次减小（敏感度依次减小）。在较低的通风量和粪便高度变化区间,CH4排放通量变化的敏感性要高于较高的通风量和粪便高度变化区间,但对于粪便温度变化趋势正好相反。     

The Resistance to Air Flow of Farm Building Ventilation Components

The static air pressure change (pressure drop) across a variety of ventilation components used in agricultural buildings was measured. Twenty-one ventilated wall claddings and ten roof ventilation arrangements were tested. The pressure drops across these items were measured at air approach speeds between 0·05 and 1·7 m/s. Despite the low Reynolds number of the air flow involved, pressure drops varied with the square of air velocity. This allows the pressure drop characteristics of the items measured to be described by a pressure loss coefficient, k. The values of k for the various items tested are given. The use of k, which simplifies the calculation of pressure losses in complex ventilation paths, is described.     

基于规模化养殖的禽舍通风系统控制平台设计

设计了基于规模化养殖的禽舍通风系统控制平台。以手机App移动终端作为远程控制终端，以STM32F103单片机为核心，结合外围功能模块，设计现场硬件控制终端。用户可通过手机App移动终端远程实现现场硬件控制终端的分时预约控制、实时监控等功能，也可通过功能按键，手动设置现场硬件控制终端的工作方式，实现单路交流电输入、多路交流电输出控制，进而实现后续多路通风排气扇工作状态有效控制。该平台灵活、简单，满足规模化禽舍通风的要求。      

Kleingrass growth and utilization by growing steers

A model of kleingrass (Panicum coloratum L.) growth and utilization by steers is presented. The model included stochastic inputs of climatological characteristics, water retention at different soil depths, rainfall runoff, potential evapotranspiration, forage growth, forage intake and steer performance. The model was used in a 2 × 3 × 4 factorial experiment where the factors were energy systems (ARC, 1965 versus NRC, 1976), stocking rates (2·47 head per hectare, 4·32 head per hectare and 6·18 head per hectare), and four management options. Individual steer weights by months were not significantly affected by the use of either energy system. Steer weights at the end of the grazing season were affected (F = 0·06) by energy system, the NRC system predicting 7·2 kg per head more liveweight gain than the ARC system. The light stocking rate had greater (P = 0·01?0·13) daily gains over months than the heavier stocking rates. The heavy stocking rate resulted, however, in greater (P < 0·05) production per hectare per year than the lighter stocking rates. Season-long production per hectare favored (P < 0·1) management options that removed steers immediately after forage was consumed rather than anticipating rainfall and new forage growth. The light stocking rate had the least mean seasonal production per hectare (P < 0.·05) but also had the least year-to-year variability. The heavy stocking rater yielded the greater (P < 0·05) mean seasonal production per hectare but the year-to-year variation was much greater. It was emphasized that the use of such probabilities of production could aid the grazier in making stocking rate and related decisions.     

自然通风温室及通风量研究

介绍了自然通风温室的通风机理和测量通风量的方法；论述了国外学者通过试验和非线性拟合后得到的通风量与温室室内外温度差、室外风速的关系及结论。     

基于CFD的育肥猪舍压力场和速度场的研究

本研究选取山西某猪场的育肥舍为研究对象,针对夏季纵向通风模式运用采用CFD中的ANSYS FLUENT软件方法进行模拟与研究,主要针对夏季纵向通风模式,重点,研究舍内压力场与速度场。从舍内压力场与速度场模拟结果反向验证传统通风计算的正确性。     

猪舍消杀巡检机器人系统设计与试验

针对规模化猪舍人工劳动强度大、重复作业多、疫病传播与防控形势严峻等问题,设计了猪舍消杀巡检机器人系统。该系统融合基于2D激光雷达的即时定位与建图(Simultaneous localization and mapping, SLAM)和超宽带(Ultra wide band, UWB)技术,实现舍内地图构建和系统实时定位;在确定热红外模组安装高度为125cm和安装倾角水平向下夹角5°的基础上,运用Jetson Xavier NX边缘计算单元进行视觉处理与识别算法的部署,完成在线猪只体温巡检;边缘计算单元依据终端指令对消杀模块中超声波雾化单元、紫外线辐射单元等进行决策控制,实现多模式舍内环境消杀;通过传感器技术对舍内环境参数进行实时监测;并搭建人机交互界面,实现监测信息的显示、报警、存储等。测试结果表明,该系统可完成地图构建、自动导航、猪只体温检测,记录异常猪只热红外图像及圈舍所在位置;依据设定的消杀模式,在目标点开启相应消杀功能的准确率为100%;机器人在巡检状态和静止状态下,舍内CO2浓度、温度、相对湿度的相对误差分别为0.04%、3.00%、2.10%。本研究可为疫情形势下猪舍巡检消杀少人化/无人化作业提供技术装备参考。     

基于CFD的育肥猪舍压力场和速度场研究

选取山西某猪场的育肥舍为研究对象,针对夏季纵向通风模式采用CFD方法进行模拟,从舍内压力场与速度场模拟结果反向验证传统通风计算的正确性。     

An Evaluation of Heating and Ventilation Control Strategies for Livestock Buildings

Thermal responses and supplemental heat consumption of a livestock building airspace were investigated using a simulation program and Typical Meterological Year weather data for a cold (-23 to -32°C) and a warm day (-4 to 7°C) in the Canadian Prairie Region. Three different control strategies using different sizes of heating/ventilating equipment and different controller time constants were evaluated. In an either-or-temperature (EOT) control, stage 1 ventilation was provided continuously by fan 1; stage 2 ventilation and the heater were controlled by the same temperature actuated switch such that either the heater was on or stage 2 ventilation fan 2 was on, but not both. In an either-or-neither temperature (EONT) control, stage 1 ventilation was provided continuously and the heater and stage 2 ventilation were controlled by separate actuated switches with a fixed interstage differential. In a temperature-humidity control (THC), all stages of ventilation were controlled thermostatically and the heater was controlled by a humidistat. THC control strategy provided the best thermal response and used the least supplemental heat. EOT control could achieve a variable ventilation rate for moisture control when fans and heater were correctly designed. EONT control provided good temperature control but failed to control humidity. Oversizing of heating/ventilating equipment resulted in poorer thermal response and higher energy consumption for EOT and EONT systems but had little effect on the THC system. Controllers with large time constants economized the use of supplemental heat but introduced poor thermal responses for all three control strategies.     

Comparison of Predicted and Measured Air Flow Patterns in a Mechanically Ventilated Livestock Building without Animals

Air flow in a section from a full scale livestock building has been simulated using PHOENICS, a computational fluid dynamics program, to give the mean velocity and turbulence energy distribution under isothermal conditions. The section has sloping ceilings, an air intake at the apex, and side-wall extractor fans. A narrow inlet gap creates the horizontal air jet which is the basis of the ventilation system. A summer ventilation rate of 44 air changes per hour was simulated, with a Jet Momentum Number of 0·0076 and an inlet Reynolds Number of 5x10r4 based on a gap size of 0·1 m and a mean velocity of 6·1 m sr-1. Calculated mean air velocites within the section were in close agreement with values measured by a sonic anemometer. Despite its known shortcomings, use of a standard turbulence model to simulate the turbulence energy generation and dissipation gave good predictions of turbulence energy distribution.     

Replacement policy in dairy herds on farms where heifers compete with cows for grassland: Part 2-Experimentation

Replacement policy is not easy to determine on dairy farms where heifers compete with cows for grassland. Using a computer simulation model of this farm situation, two factorial experiments were conducted to evaluate quantitatively the effect of different replacement rates on profitability and herd improvement.The variables changed in herds of average health and very good health were replacement rate (0·14, 0·22, 0·30), age at first calving (36, 24 months), calving index (13, 12 months) and AI sire merit (standard, premium). Initially, the experimental herd had average health, a replacement rate of 0·22, a calving index of 13 months, calved its heifers at 36 months and had been using standard bulls for many years.After 15 years, the increase in the level of a sinking fund when the age at first calving was reduced was between three and five times greater than when premium bulls were used, calving index was reduced or herd health was improved. There was a major interaction between replacement rate and age at first calving.Yield per cow was significantly reduced (P≤0·001) by reducing the age at first calving and significantly increased when premium bulls (P≤0·001) were used or when herd health was improved (P≤0·05).Some treatments were not tested as expected due to the restraining effect of a 13-month calving interval on the availability of cows for breeding pure in a seasonally calving herd.     

规模化猪舍废气复合净化系统设计与试验

为解决规模化猪舍废气排放造成的环境污染问题,设计了一种猪舍废气复合净化系统。该系统采用化学法与水洗法相结合,通过PLC（可编程逻辑控制器）控制系统实时采集净化系统内的pH值、电导率、液位和压差等动态环境数据,智能控制洗涤泵启停和电磁阀通断,自动完成供水、加酸、喷淋和排废4个工作环节。同时,控制系统采用MCGS触摸屏与PLC建立通讯,通过创建人机交互界面实现系统环境数据监测、运行状态流动显示、按需配置系统参数和报警信息输出等多种功能,实现了系统操作的人性化和过程的可视化。系统可根据实际应用中对净化效率和运行成本的要求,实现多种控制模式,均有效抑制了猪舍废气排放。试验结果表明,系统对主要污染成分氨气的平均去除率可达到85%,整体运行可靠、控制简单,经济成本量化清晰。该系统在江西某种猪场实施应用,成效显著,可为畜禽养殖环境废气净化处理的工程应用提供参考。     

水合物法储存温室气体二氧化碳的可行性分析

全球变暖的主要原因是由于大量温室气体排放导致了温室效应,而温室气体的主要组成部分就是二氧化碳,因此二氧化碳应作为温室气体削减与控制的重点.论述了海洋储存二氧化碳与二氧化碳置换开采天然气水合物中甲烷的可行性及环境效应.该方法以固态二氧化碳水合物的形式储存大量的二氧化碳,有利于大大降低大气中二氧化碳的含量,有利于维护海底水合物沉积层的稳定性,有利于提高开采天然气水合物中甲烷的安全性,为二氧化碳水合物储存温室气体二氧化碳开辟了一条新的途径,对保护环境和经济社会的可持续发展具有重大的现实意义.     

The Effect of Collaboration between Cattle Farms on the Labour Requirement and Machinery Costs

Danish farming is based on the principle of freeholding, but interest in alternative types of ownership is increasing, one of the reasons being the high labour pressure on small farms in particular, where each family has to carry out the work on their own. Moreover, the initial capital investment is high, and earnings are often low.In a study of six milk-producing farms, the potential benefits of joint ownership were examined for field work and for livestock operations. On the establishment of a joint ownership, analyses showed that the number of annual workers can be reduced from 16·8 to between 10·8 and 11·4, if joint field operations are established together with a common feed mill from where feed is distributed daily to the individual cow houses. The number of annual workers can be further reduced to 8·8 if all cows are housed in a joint cow house.Labour and machine costs for five field plans vary from DKK 3063 to 2515 per ha–highest for the plan with beet and lowest for the plan with straw.Labour and machine costs on feeding vary from DKK 2056 to 1811 per year-cow and rearing stock but if all the animals are gathered in a common cowhouse, the costs can be reduced to DKK 1686 per year-cow and rearing stock.