전산유체역학을 사용한 양돈장 내 작업환경 환기효율성 분석

Analysis of Working Environment and Ventilation Efficiency in Pig House using Computational Fluid Dynamics

Abstract

The internal environment in pig house is closely related to the animal productivity. In addition, it is important to consider a working environment inside the pig house due to high gas and dust concentrations. The poor working environment inside the pig house can cause health problems including respiratory diseases. To analyze the working environment, it is important to evaluate the ventilation efficiency to effectively remove harmful gases and dust. The purpose of this study is to develop a 3D CFD model to analyze the working environment in the pig house. CFD model was validated by comparing air temperature distributions between CFD computed and field measured data. The average air flow rate at the pig height was 40.1 % lower than the working height when incoming air was concentrated on upper layer by the installed ventilation system on the experimental pig house. Using the validated CFD model, the regional ventilation efficiency was computed by the TGD(tracer gas decay) method at the pig and working heights. There was a difference of ventilation efficiency on 14 % between the air stagnated section and the rest sections. Stagnated gas concentration can be effected by animal and human health.

Fig. 1 Satellite image of experimental pig farm surrounded by mountain area in Yeonggwang, Korea; blue arrow represents the intaking direction of outside air

Fig. 2 Airflow image of experimental pig farm

Fig. 3 Ventilation system operated during spring season with various outlet(red) and inlet (blue)

Fig. 4 Temperature and humidity sensor locations installed inside and outside the experimental pig room; HOBO data logger was used for sensor 1∼9 and IC(inside climate) and Weather Station was used for sensor OC(outside climate)

Fig. 5 Mesh design of the experimental pig house

Fig. 6 Field monitoring data for validation of CFD model considering steady state condition

Fig. 7 Locations of each pen for analysis of internal environmental conditions in the experimental pigroom

Fig. 8 Comparison of turbulence model using internal thermal distributions between field measured and CFD computed temperatures

Fig. 9 Thermal distribution at working height between field measured and CFD computed data

Fig. 10 Airflow pattern computed by CFD simulation; color of arrows represents air velocity magnitude ranged from 0∼5 m/s

Table 3 Environmental conditions including air velocity, temperature, and ventilation efficiencies computed by TGD using CFD simulation according to the pig and human respirable heights

Table 1 Daily feed energy coefficient used for calculating pig heat-production (CIGR, 2004)

Table 2 Input & boundary conditions for the CFD simulation model of the experimental pig house

Table 4 Distribution of CO₂ concentration in the experimental pigroom by heights at 60 seconds after starting the ventilation system using fresh outside air with CO₂ concentration of 400 ppm when CO₂ gas was initially disturbed by 2,000 ppm