Quantitative Detection Model of Pernicious Gases in Pig House Based on BP Neural Network

To find a neural network model suitable to identify the concentration of mixed pernicious gases in pig house, the quantitative detection model of pernicious gases in pig house was set up based on BP （ Back propagation） neural network. The BP neural network was trained separately by the three functions, trainbr, traingdm and trainlm, in order to identify the concentration of mixed pernicious gases composed of ammonia gas and hepatic gas. The neural network toolbox in MATLAB software was used to simulate the detection. The results showed that the neural network trained by trainbr function has high average identification accuracy and faster detection speed, and it is also insensitive to noise; therefore, it is suitable to identify the concentration of pemidous gases in pig house. These data provide a reference for intelligent monitoring of pemicious gases in pigsty.

Numerical Simulation of Natural Ventilation in Northern Civil Pig Houses

With northern pig house as study objective,the 3-D numerical simulation of natural ventilation airflow field of five pig houses with different window area was done by using Fluent software,and the comparative analysis was carried out on simulation result and measured result.The results showed that the effect of ventilation was decided by the reasonable area ratio of window and earth and the ratio of length and width of window.According to this real pig house in experiment,there are the best uniformity of ventilation and the least area of having no ventilation by 1：10 of the area ratio of the window and earth in the pig houses,the smaller air retention zone by the smaller ratio of length and width of window,the better effect of ventilation;the results of simulation agree well with the results of measured,the max relative error and the average error was 11.1% and 7.7%,so the software of Fluent was proved effective in the numerical simulation of natural ventilation in the pig houses and the optimal design of pig houses＇ structure.

Design of Environmental Monitoring and Control System for Large-scale Pig House with Fermentation Bed

The design and assembly of environmental monitoring and control system for large-scale pig house with fermentation bed helped to solve the problem of environmental automatic control in piggery.The sensors would monitor the temperature,humidity,light,wind direction,wind speed,CO2,NH3and other parameters.On-line real-time data collection was achieved.The expert system was constructed to control the temperature in piggery below 30℃,to control the air and mattress humidities higher than 65%.Under the conditions of different season or different wind speed,even in day and night,the control actuators were different.The actuators included fanning wet curtain,lighting,micro spraying,spraying,propeller fan,electric aluminum alloy shutter and spraying systems on the roof.The actuators were integrated,and they control the piggery environment simultaneously.The system also designed the remote video monitor interface,parameter-monitoring curved interface and operation interface,which provided a good man-machine interface.

Characteristics of Microbial Aerosol Pollution in Pig Houses

[ Objective] To explore the characteristics of microbial aerosol pollution in different pig houses and provide theoretical foundation for risk assessment of microbial aerosols on human and animal health. [Method] Gestation house, nursery house and fattening house in suburb of Beijing were chosen as research objects, and the concentration, size distribution and composition characteristics of the airborne microorganisms were determined. [ Result] The concentrations of airborne microorganisms were completely different in different houses under the influences of ventilation, methods of cleaning manure and pig populations. The highest concentration of airborne microrganisms was the nursery house. The particles with diameter size of 0.65 -2.10 μm carried 26% -27% heterotrophic bacteria and 39% -43% fungi. They could reach alveolus of humans and animals and thus made infectious threat to health of humans and animals. The dominant heterotrophic bacteria genera were composed of Bacil/us and Pseudomonas; and the dominant fungi were Penicillium and Muco. [ Conclusion] Concentrations of airborne microorganisms are completely different in different houses. However. there is no sianificant difference between the microbial composition and tyee of oia houses.

Effect of partial pit exhaust ventilation system on ammonia removal ratio and mass transfer coefficients from different emission sources in pig houses

A partial pit exhaust ventilation(PPEV)system installed below the slatted floor has been widely used in fattening pig barns nowadays in Denmark.Experimental tests showed that annually around 50%of ammonia emissions was collected by PPEV system.However,the percent of emissions collected by PPEV system from different emission sources including slurry manure surfaces,top surfaces,bottom surfaces and side surfaces of the slatted floor has not been investigated as well as the mass transfer coefficients.This study applied CFD modeling to investigate the removal ratio of ammonia emissions from four emission surfaces including the top,side,bottom surfaces of the slatted floor and slurry manure surfaces.The CFD model was validated by experimental air speeds measured in a room equipped with two full-scale pigpens.The validated CFD model was further adopted to simulate cases under five ventilation rates(2000-4000 m^(3)/h),four emission sources and two locations of PPEV system exhaust.The results showed that the removal ratios of ammonia emissions by PPEV system from the four emission sources were generally higher for the cases that the PPEV exhaust was installed opposite to the air supplier than the values of those cases that the PPEV exhaust was located at the same side of side wall air supplier.The removal ratios of ammonia emissions were the highest with the emission source of slurry manure surface and generally 30%higher than the values of other cases.The mass transfer coefficients with the emission sources on the side surfaces of the slatted floor were the largest.The results indicated that the airflow patterns and locations of emission sources greatly influenced the removal ratios of ammonia emissions and ammonia mass transfer coefficients.

OPTIMIZATION OF THE VENTILATION SYSTEM FOR A FORCED VENTILATION PIGGERY

Pigs are subjected to intensive environment control and management in order to achieve higher productivity.This is due to their sensitivity to climatic variation,which strongly affects their growth.This paper reports the design optimization of a forced ventilation piggery using computational fl uid dynamics.This numerical investigation determined the effect of varying the number of ventilation openings and their location on the air fl ow pattern,speed,temperature,power needed,ability to remove heat and residence time.The effect of varying the ventilation rate in a range(0.05–0.8 m3/s),and ambient temperatures of 5°C and 32°C was also investigated.The modeled piggery has dimensions 40 m×15 m×2.6 m,with central walkway and gable roof with the apex at 3.9 m and is a common design in Australia.A steady-state two-dimensional numerical model based on the integral volume method,including the effects of buoyancy and heat generated by the pigs,was solved using the computational fl uid dynamics software“Fluent.”Four designs were investigated and an optimum design,which facilitates better ventilation of the majority of the room,has been identifi ed.In summer,an inlet velocity has been recommended which achieves optimum environment inside the piggery meeting the pigs’thermal comfort criteria with minimum power usage.During winter it became obvious that heating has to be used in all designs to be able to meet the pigs’thermal comfort criteria.