Environmental problems and improvements depending on partition type 72

The types of partition that are mainly used in swine house are pipe fence type and panel type. The pipe type is fixed and air flow can be formed at the interval between the partitions. The panel type is light and portable, so it is easy to distinguish the swine group. However, because it is blocked, air flow can be disturbed. Therefore, the environmental factors near the swine according to the partition type were analyzed.

Fig. 37 Vector field and temperature contour near the swine group according to the fence type

Fig. 45 below shows the vector field and temperature contour around the swine. The pipe type partitions have air flow smoothly between swine.

However, in the case of the panel type, it can be seen that air flow is blocked in

the partition. The average velocity of air near the swine is 1.31 m/s when the pipe is used and 0.42 m/s when the panel is used. As a result, the temperature difference around the swine was about 3-4℃. Therefore, it was considered that it would be possible to prevent the high temperature stress by providing fresh air near the swine using pipe type partition in the summer season. On the other hand, if a pipe type is used, disease spread can occur between swine mouth-to-mouth. So, the farmers will have to design the swine room considering this problem.

5. Conclusion

The purpose of this study was to evaluate the major environmental problems and aerodynamic improvement measures of the domestic swine house. For this purpose, CFD models were developed and simulation analysis was performed considering all ventilation systems. The target animal was chosen as a 7-8 weeks old swine which are sensitive to environmental changes. Based on this, a CFD model was designed and analysis cases were designed to evaluate the improvement.

Analyzing the computed results, various environmental problems and evaluated various methods to improve them in winter and summer season.

First, field investigation and literature survey were carried out in order to elucidate the major environmental problems occurring in domestic swine farms. In winter, there were the problem of low temperature, humidity and ammonia accumulation which are caused by operating with minimum ventilation. CFD simulation was performed to analyze environmental factors according to the ventilation systems. In summer, there were internal high temperature problems, and evaluation was made according to the calculation method of maximum ventilation rate.

In order to simulate various ventilation systems, a swine model and a lot of ventilation system model were designed considering heat, vapor and ammonia. The

validation of the simulation model is based on the results of the previous research.

The minimum grid size is 0.1 m and the turbulence model is Realizable k-w model.

In winter season, when using the side slot, it was confirmed that the cold air directly reaches the swine. The temperature distribution was about 23℃. And it is below the range of 25-28℃ which is the optimum growth temperature range. In order to improve this temperature problem, it was shown that when using the ceiling hole inlet type, it is about 2℃ higher. The temperature of the outside cold air could be increased in the space of the ceiling. However, there were problems that the humidity and the ammonia were accumulated highly. When the pit fan is used, it is analyzed that the ammonia gas generated from the manure can be removed before rising to the swine because the pit is exhausted from the lower part of the pit, thereby being reduced by about 33%. However, it is essential to increase the ventilation rate to lower the ammonia concentration to an appropriate level.

When the ventilation rate is adjusted, the temperature falls below the appropriate level. It is analyzed that the temperature, humidity and gas can reach the appropriate level through the heating devices. Also, if the gap of the door and shutter were not sufficiently sealed, the infiltration may occur. As a result of the analysis, it was found that unnecessary external air could reach to the swine group.

Therefore, it is necessary to be careful about sealing the gap.

In summer season, high temperature problems have occurred in most ventilation systems. According to the ventilation rate of the 2009 Korean Standard, it should be operated higher than that of MWPS method. However, there was no significant difference between the two ventilation methods. It is possible to control the internal environment sufficiently even if operated with MWPS. Also, when operating with 2009 Korean Standard, the air flow exceeding the performance of the installed ventilation fan was required. This can cause some trouble of the ventilation fan. If the ventilation rate is too high, the odor and gas exhausted to the outside can increase, and complaints of nearby residents may occur. It can also affect the temperature distribution around the swine depending on the type of

partition. The panel shape can block the air flow and increase the temperature around the swine. The shape of the pipe is advantageous in order to lower the sensation temperature due to the wind formed around the swine. Considering the winter and summer operating conditions, it is suggested to use ceiling hole inlet type. In winter, it is effective to increase the ventilation rate and use the heating device. In summer, it is preferable to operate with MWPS ventilation.

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국문 초록

국내 자돈사의 주요 환경 문제에 대한 공기역학적 개선 방안 분석

김준규 생태조경·지역시스템공학부 지역시스템공학 전공 서울대학교 대학원

최근 육류위주의 소비가 증가함에 따라 국내 농업 생산액 중

축산업은 꾸준히 증가하여 약 43%를 차지하고 있다. 이중에서도 양돈

생산액은 가장 많은 양을 차지하고 있으며, 농촌의 양돈 종사자가 줄어들고 있는 상황에서 농가당 대량 생산이 요구되고 있는 실정이다.

이에 따라, 많은 양돈시설들이 대형화되고 있으며, 대형화된 시설에서 밀집사육을 통해 돼지의 생산량을 극대화하고 있다. 그러나 이러한 대형화된 시설에서 내부 환경조절은 돼지의 생산성에 매우 밀접하다고 할 수 있다. 내부 사육 환경이 적절하게 유지되지 못하면 사료효율이 감소하게 되어 오히려 생산성이 떨어지며, 질병 노출에 취약해지게 되어 급기야 폐사에 이를 수 있다. 최근까지도 구제역 등의 질병으로 인한 피해사례가 빈번하게 발생하고 있는 실정이다. 특히, 어린 돼지들은 환경 변화에 민감하여 동절기, 하절기, 환절기와 같은 시기에 적정 생육환경을 제공하지 못하면 쉽게 폐사에 이를 수 있다. 이와 같은 이유로, 돈사 내부의 환경 조절은 매우 중요하다고 할 수 있다.

한편, 국내 돈사 시설은 재래식 돈사가 많은 비중을 차지하고 있으며, 최근 표준 설계도가 출판되었지만, 아직까지도 대부분 노후화된 축사로 이루어져 있다. 특히 많은 농가에서는 기존의 재래식 돈사를 개조하여 운영하고 있으며, 농가마다 환기 구조가 상이하며 농가의 경험적인 방식으로 운영을 하기 때문에 환경 조절을 위한 표준화된 운영

방침이 미비한 실정이다. 또한 최근 폭염, 한파와 같은 극한 기후

설정하였다. 돼지의 발열, 호흡으로 인한 수분발생, 분뇨에서 발생하는

하절기 국내 환기량 운영 기준은 해외 MWPS 환기량보다 높게 산정하여 운영하도록 고시되어 있다. 이를 CFD 모의한 결과 MWPS

환기량으로 충분히 온도, 습도, 암모니아 제어가 가능한 것으로

분석되었다. 또한 국내 기준 환기량을 적용할 경우, 농가에 설치된 환기팬의 최대 풍량보다 높게 운영되어 환기팬에 부하가 발생하여 팬의 노후화를 야기할 수 있다. 또한 환기량이 높을수록 외부로 배출되는 악취 및 가스의 양이 증가하게 되어, 인근 농가의 민원이 늘어나는 문제가 발생할 수 있다. 따라서, MWPS 환기량 기준으로 운영할 필요가 있다. 한편 하절기 자돈 주변으로 열섬현상이 발생하여 고온스트레스 문제가 주로 발생한다. 이에 자돈 주변에 신선한 공기가 원활하게 제공되어야 하며, 체감온도를 낮추기 위해서 적정 유속을 유지해야 한다.

자돈을 구분하는 칸막이의 형태가 판넬일 경우 공기의 흐름을 차단하여 돈군 주변으로 온도가 올라가는 문제가 발생한 것으로 분석되었다.

파이프 형태를 이용할 경우, 공기의 흐름이 원활하여 열을 충분히 제거하고 자돈의 체감온도를 낮춰주는 효과가 있을 것으로 사료된다.

따라서, 하절기 최대환기량은 MWPS 기준으로 운영하며, 칸막이 형태는 울타리 형태가 적합할 것으로 판단하였다.

본 연구 결과, 동절기 저온 문제 해결을 위해서는 중천장 천공 입기 방식 및 피트배기 팬을 활용하는 것이 적합하다. 그러나 습도 및 암모니아 문제를 동시에 해결하기 위해서는 환기량을 상향조절할 필요가 있다. 이에 따른 온도는 보온장치를 활용하여 보충하는 것이 적합하다.

하절기 최대환기량 운영시 국내 기준의 상향조절된 환기량으로 운영할 시 과도한 풍량이 발생하여 팬에 부하가 발생할 수 있으며, MWPS 기준 환기량으로 충분히 환경제어가 가능하므로, MWPS 기준 환기량으로 운영하는 것이 적합하다. 또한 돈군 주변의 고온 문제를 해결하기

하절기 최대환기량 운영시 국내 기준의 상향조절된 환기량으로 운영할 시 과도한 풍량이 발생하여 팬에 부하가 발생할 수 있으며, MWPS 기준 환기량으로 충분히 환경제어가 가능하므로, MWPS 기준 환기량으로 운영하는 것이 적합하다. 또한 돈군 주변의 고온 문제를 해결하기