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수치 해석을 이용한 단일 마이크로채널의 단면 가열 조건의 열전달 특성에 관한 연구
최치웅(Chi-woong Choi),허철(Cheol Huh),김동억(Dongeok Kim),김무환(Moo Hwan Kim) 대한기계학회 2007 大韓機械學會論文集B Vol.31 No.12
The microchannel heat sink is promising heat dissipation method for high density electronic devices. The cross-sectional shape of MEMS based microchannel heat sink is limited to triangular, trapezoidal, and rectangular due to their fabrication method. And heat is added to one side surface of heat source. Therefore, those specific conditions make some complexity of heat transfer in microchannel heat sink. Though many previous research of conjugate heat transfer in microchannel was conducted, most of them did not consider heat loss. In this study, numerical investigation of conjugate heat transfer in rectangular microchannel was conducted. The method of heat loss evaluation was verified numerically. Heat distribution was different for each wall of rectangular microchannel due to thermal conductivity and distance from heat source. However, the ratio of heat from each channel wall was correlated. Therefore, the effective area correction factor could be proposed to evaluate accurate heat flux in one side heating condition.
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홍순중(Soonjung Hong),백이(Yee Paek),강동현(Donghyeon Kang),김효철(Hyocher Kim),이상희(Sanghee Lee),문석표(Seokpyo Moon),민병규(Byeonggyu Min),남영조(Youngjo Nam),권승귀(Seunggwi Kwon),김동억(Dongeok Kim) 한국산학기술학회 2023 한국산학기술학회논문지 Vol.24 No.7
최근 국내 농촌인력의 고령화와 인구감소로 인하여 인력 수급의 어려움 등으로 농촌 노동력 부족현상이 심화되어 농작물 생산에 어려움이 가중되고 있다. 본 연구에서는 양파 재배농가의 노동력 부족문제를 해결하기 위해 양파 수확작업에 필수적인 줄기절단기를 개발하여 농용트랙터에 줄기절단장치를 부착하였으며, 줄기절단시험을 실시하였다. 엔진의 회전수 증가에 따라 PTO 회전수의 편차는 다소 있으나 엔진회전수 증가에 따라 PTO 회전수는 증가되었다. PTO 540 rpm으로 고정을 한 후 엔진의 회전수가 1,600 rpm일 때 줄기 절단율은 53.1%, 미절단율은 43.8%, 극절단율은 3.1% 및 손실율은 0%로 나타났고 1,800 rpm일 때 줄기 절단율은 64.1%, 미절단율은 31.3%, 극절단율은 4.7% 손실율은 0%로 나타났다. 2,000 rpm일 때 줄기 절단율은 64.1%, 미절단율은 18.8%, 극절단율은 17.2% 및 손실율은 0%로 나타났다. 양파 줄기절단기 작업시간은 10a 당 기계작업시 0.6시간, 인력작업은 10시간이 소요되었으며 작업성능은 인력에 비하여 약 16배 노력절감의 효과가 있는 것으로 분석되었다. 향후, 포장조건에 따른 작업성능을 높일 수 있는 연구가 추가적으로 필요할 것이다. Recently, the shortage of rural labor in South Korea has intensified due to the aging and decrease of the population. This is resulting in difficulties in finding workers and has added to the difficulty in producing crops. Therefore, to solve the labor shortage problem of onion growers, a stem cutter for harvesting onions was developed and attached to an agricultural tractor in this study. The number of engine revolutions varies slightly, and the change in power take-off (PTO) increases with the number of engine revolutions. When fixing the PTO at 540 rpm, the rate of cut stems was 53.1%, the rate of uncut stems was 43.8%, the rate of extreme cuts was 3.1%, and the loss rate was 0%. At 1,800 rpm, the rate of cut stems was 64.1%, the rate of uncut stems was 31.3%, and the rate of extreme cuts was 0%. At 2,000 rpm, the rate of cut stems was 64.1%, the rate of uncut stems was 18.8%, the rate of polar cutting was 17.2%, and the loss rate was 0%. The work time of the onion stem cutter was 0.60 hours per 10a, which would have taken 10 hours to do manually. The cutter saved about 16 times more effort compared to manual labor. However, there is still a need for research to improve work the performance according to field conditions.
ScienceON
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