예냉 처리가 치콘의 MA 저장성에 미치는 영향

정현진(Hyun Jin Jung),서현택(Hyun Taek Seo),최인이(In-Lee Choi),유태종(Tae-Jong Yoo),손진성(Jin-Sung Son),원재희(Jae Hee Won),김일섭(Il Seop Kim),강호민(Ho Min Kang) (사)한국생물환경조절학회 2010 생물환경조절학회지 Vol.19 No.4

본 연구는 예냉처리가 치콘의 MA저장에 미치는 영향을 알아보고자 실시하였다. 치콘의 예냉은 강제송풍예냉처리에 빠르게 진행되어 품온이 예냉 목표 온도인 2±1℃까지 저하되는데 소요시간이 강제송풍예냉이 자연통풍식의 1/6 수준이었다. 반냉각시간은 자연예냉이 3시간 21분, 강제통풍식이 1시간 17분이었다. 저장중치콘의 생체중은 5℃와 10℃ 저장에서 모든 처리구가 0.5% 미만의 감소로 극히 적었으며 예냉시간이 짧았던 강제송풍예냉이 가장 높게 유지되었다. 저장중 포장재내 산소와 이산화탄소 그리고 에틸렌의 농도변화는 5℃에 비해 10℃에서 변화폭이 컸다. 예냉에 의한 호흡억제 효과는 5℃에서 나타나지 않았으나, 10℃에서 저장 9일 이후 대조구보다 낮은 이산화탄소와 높은 산소 농도로 확인되었다. 에틸렌은 예냉처리구가 저장 3일까지 대조구에 비해 다소 낮았으나 저장 6일부터는 처리간에 차이를 보이지 않았다. 저장 15일째 조사한 외관상 품질은 5℃와 10℃ 모두에서 대조구에 비해 예냉처리구에서 높게 유지되었는데, 예냉처리별로는 예냉기간이 훨씬 짧았던 강제송풍예냉에서 품질저하가 자연예냉보다 더 컸다. 이는 6.0m/sec 강한 송풍으로 치콘의외옆 일부가 물리적 상처를 입었기 때문이라 판단되어 송풍속도 등에 대한 세밀한 추가 실험이 요구된다. The effects of precooling treatments on the storability of chicon were investigated during modified atmosphere (MA) storage. The forced air cooling showed faster precooling rate that reduced the internal temperature of chicon to 2 ±1℃, and the precooling time of forced air cooling was 1/6 of room cooling. The half cooling time was 3 hr 21 min in room cooling and 1 hr 17 min in forced air cooling. Weight loss was less than 0.5% in all treatments both 5℃ and 10℃ MA storage and maintained higher in forced air cooling treatment. The concentration of carbon dioxide, oxygen, and ethylene of 50 ㎛ ceramic film packages were observed higher at 10℃ than 5℃. The precooling effect on respiration reduction was not shown at 5℃, but appeared that the gas concentration of precooling treatments showed less carbon dioxide and higher oxygen than non precooling treatment by 9 days after 10℃ storage. Ethylene concentration of precooling treatments showed lower than non precooling treatment until 3 days both 5℃ and 10℃ MA storage. Precooling showed the effect on maintaining visual quality of chicon both 5℃ and 10℃ MA storage. However, the forced air cooling that showed faster precooling rate did not appeared more precooling effect on the visual quality than room cooling because the fast air flow (6.0 m/sec) of forced air cooling hit directly on chicon outer leaves and might cause physical damage to chicon. Although the forced air cooling showed the effect on maintaining quality of chicon, but additional studies should be needed that investigated proper air flow rate and cooling box structure can prevent physical damage by air flow.

Thermal Stress Model of Transversal Forced Air-Cooled Capacitor Banks for MWPower Converters

Zhijian Yin,Rui Wu,Morten Hygum,Yongheng Yang,Huai Wang 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Capacitor banks are key components in high power applications, the reliability of which affects the overall system lifetime. It is known that the thermal stress in each capacitor can affect the lifetime performance of the entire capacitor bank. In this paper, an analytical thermal model is presented to estimate the average capacitor thermal stress in a transversal forced air-cooled three-phase AC-filter capacitor bank for MW-level power converters. The proposed model calculates the thermal resistance of a capacitor bank considering power losses, geometry, cooling conditions and physical arrangement. With a conventional Foster thermal network, the hot-spot temperature and case temperature for each capacitor can be obtained. The experimental results on a full-scale three-phase filter capacitor bank consisting of 27 film sub-capacitors have demonstrated the effectiveness of this model.

400kW급 IGBT 인버터용 방열 시스템 설계

이진우 전력전자학회 2004 전력전자학회 논문지 Vol.9 No.4

본 논문에서는 열원인 전력용 반도체 소자와 방열판 및 팬으로 구성된 강제 냉각방식 방열 시스템을 먼저 해석 가능한 요소로 나눈 후 각 요소에 대한 해석적이거나 실험적인 설계 식을 제시하고 이를 적용한 설계 방법을 제안하였다. 제안한 방법으로 400kW급 IGBT 인버터용 강제 냉각방식 방열 시스템을 설계하고 제작하였다. 실험결과는 설계 온도가 실험치에 대해 10[%] 오차 범위 내에서 잘 일치함을 검증하여 제안한 해석적인 정상상태 설계방법의 타당성을 보였다. This paper deals with the design of a heat dissipation system, which consists of a heat source of power semiconductor devices, a heat sink and a fan for the forced air cooling. It suggests the method of appropriately dividing the whole heat transfer system into analytical subsystems and also presents the correspondent analytic or experimental design equations for the subsystems. The experimental results on the designed heat dissipation system for the 400kW IGBT inverter show less than 10[%] error with respect to the design temperature and therefore verify the validity of the proposed analytical design method in the steady state.

열유동 연성해석을 통한 대용량 직접구동형 발전기 냉각시스템의 적합성 평가

박형준(Hyung Joon Park),한승호(Seung Ho Han) 대한기계학회 2021 大韓機械學會論文集B Vol.45 No.1

해상의 일정한 풍속과 우수한 풍질로 해상풍력발전기가 선호되는 추세이나, 설치비용 및 유지 · 보수 비용이 상대적으로 높아 단위 발전기당 발전용량을 올리기 위하여 터빈이 대형화되고 있다. 저자 등에 의해 제안된 대용량 6.2 MW 하이브리드 직접구동형 발전기는 2단의 AFPM(axial flux permanent magnet) 발전기와 RFPM(radial flux permanent magnet) 발전기를 조합하여, 단위 체적 및 중량 대비 발전량이 높은 출력성능을 보여주었다. 그러나 대용량 발전기에서는 전력 생산 시 구리 및 철 손실에 의한 발열이 심하여 고정자에서 절연손상 그리고 영구자석에서 불가역 감자현상이 나타날 수 있다. 대용량 발전기의 초기설계 단계부터 고정자 및 영구자석 주위의 열전달 특성을 분석하여 발열 시 이를 냉각시킬 수 있는 냉각장치의 설계가 요구된다. 본 연구에서는 6.2 MW급 하이브리드 발전기에 적합한 강제대류 및 히트 파이프를 이용한 공랭식과 수랭식 냉각장치를 대상으로 실제 작동조건을 고려한 전자기 및 열-유동 연성해석으로 발전기의 열전달 특성을 해석적으로 평가하였다. 고정자 절연손상의 한계온도를 규정한 IEC 60076-11에 의거하여 두 냉각장치 모두 B등급을 만족하였으며, 영구자석의 불가역 감자현상에 대한 한계온도인 90°C도 충족함을 확인하였다. Offshore wind speeds tend to be faster and steadier than land wind speed. Hence, the electricity generated by offshore wind power is higher per amount of capacity in installed wind turbines. Wind turbines used in offshore environments are generally larger and taller because of reduced building and maintenance costs. The authors developed a 6.2 MW class hybrid direct-drive generator, which was constructed in two stages using 2.5 MW axial-flux permanent-magnet (AFPM) and 1.2 MW radial-flux permanent-magnet (RFPM) machines. Because heat was significantly generated owing to copper and iron losses, the AFPM and RFPM machines experienced insulation failure of stators and demagnetization of permanent magnets under sever thermal conditions. In this study, the heat transfer in the 6.2 MW class hybrid direct-drive generator using the developed cooling systems, e.g., forced-air-type and liquid-cooled-type systems, was analyzed numerically, and the actual operation conditions were considered. The results for the thermal-fluid interaction analysis of the designed cooling systems showed that the temperatures of the stators and permanent magnets decreased significantly. The cooling systems satisfied the IEC 60076-11 requirements, in which the limit temperature of the stator insulation failure was specified, and the limit temperature for the irreversible demagnetization of permanent magnets was 90°C.

배추 력광 품종의 저장 중 1-MCP에 대한 반응

홍세진(Sae Jin Hong),김병섭(Byung-Sup Kim),김병삼(Byeong-Sam Kim),엄향란(Hyang Lan Eum) (사)한국생물환경조절학회 2018 생물환경조절학회지 Vol.27 No.2

배추를 저장하는 동안 품질을 유지하기 위한 방안으로 1-methylcyclopropene(1-MCP) 처리효과를 확인하였다. 수확된 배추는 즉시 실험실로 옮겨와 4개의 그룹(차압예냉 (forced-air cooling, FAC) 처리구, FAC + 0.03mm LLDPE film(Liner) 처리구, FAC + 2μL·L<SUP>-1</SUP> 1-MCP(1-MCP) 처리구, FAC + 1-MCP + Liner 처리구)으로 분류하여 각각의 처리를 실시한 후 2℃, 95% RH 저온에서 저장하였다. 저장중 품질변화는 무게 감모율, 가용성 고형물 함량, 경도, 그리고 색도(CIE L<SUP>*</SUP>, a<SUP></SUP>ㅇ, bㅇ, chroma, hue angle)를 통해 확인하였다. 저장기간 동안 각 실험구의 감모율은 Liner 처리에 의해서 감소하였다. 저장기간 6주가 경과되면 FAC + 1-MCP + Liner 처리구는 12.5%의 감모율을 보이면서 다른 처리구들에 비해서 감모율을 최소화하였다. 가용성 고형물의 함량은 수확 시 2.5<SUP>o</SUP>Brix였으며, 저장기간이 3주 경과되면서 FAC+ 1-MCP + Liner 처리구에서 수확 시의 값이 유지된 반면, 다른 처리구 들은 증가하였다. 배추의 경도는 수확 직후 24.0N 이었으며, FAC + 1-MCP + Liner 처리구에서 저장 6주 경과 후 22.6N으로 수확 당시의 경도가 유지되는 경향을 보였다. 저장 기간 동안 배춧잎의 색 변화는 CIE a<SUP>*</SUP>와 hue angle 값으로 확인할 수 있으며, 1-MCP 만을 처리할 경우에는 색도 변화에 영향을 미치지 않는 반면 1-MCP를 처리한 다음 Liner 포장을 실시하면 CIE a<SUP>*</SUP>와 hue angle의 변화를 최소화 시키면서 수확 당시의 색도를 유지시킬 수 있었다. 이상의 결과에서 1-MCP 처리는 배추 력광 품종 저장에는 효과가 미비하나, Liner와 함께 처리할 경우 6주까지 품질유지가 가능하였다. The effect of 1-methylcyclopropene (1-MCP) in the storability of kimchi cabbage at cold storage condition was investigated. Kimchi cabbage (Brassica campestris L. cv Ryouckgwang) was divided four groups, forced air cooling (FAC), FAC + 0.03 mm linear low density polyethylene liner (Liner), FAC + 2 μL·L<SUP>-1</SUP> 1-MCP (1-MCP), and FAC + 1-MCP + Liner. After each treatment kimchi cabbage was stored at 2℃, 95% RH. Quality parameters were weight loss, soluble solids content (SSC), firmness, and color (CIE L<SUP>*</SUP>, a<SUP>*</SUP>, b<SUP>*</SUP>, chroma, hue angle). Weight loss during storage was showed significant difference by Liner treatment. In particular FAC + 1-MCP + Liner treatment showed 12.5% reduction after 6 weeks of storage period and minimized the weight loss rate compared to other treatments. SSC of kimchi cabbage was 2.5 oBrix at harvest and FAC + 1-MCP + Liner treatment maintained the SSC until 3 weeks, while in other treatments gradually were increased. The firmness of kimchi cabbage was 24.0 N immediately after harvest and the firmness at harvest time tended to be maintained at 22.6 N after 6 weeks of storage in FAC + 1-MCP + Liner treatment. During the storage period, the color change of the kimchi cabbage leaf can be confirmed by CIE a <SUP>*</SUP> and hue angle value. 1-MCP treatment alone did not affect the color change, however 1- MCP + Liner treatment was able to maintain the chromaticity at harvest time while minimizing the change of CIE a <SUP>*</SUP> and hue angle. These results suggest that 1-MCP treatment is not effective for the storage of kimchi cabbage but can be maintained for up to 6 weeks when treated with Liner.

수확 후 전처리에 의한 고랭지 배추 ‘춘광’ 품종의 저온 저장 중 품질 변화에 대한 비교

배상준(Sang Jun Bae),엄향란(Hyang Lan Eum),김병섭(Byung-Sup Kim),윤정로(Jungro Yoon),홍세진(Sae Jin Hong) 한국원예학회 2015 원예과학기술지 Vol.33 No.2

Kimchi cabbage ‘Choon Gwang’ cultivar that was grown in highlands in Gangneung was subjected to predrying, room cooling, and forced air cooling, and then packed with/without 0.02 ㎜ HDPE film to investigate the effect of postharvest treatment on quality characteristics during 8 weeks storage at 2℃ (RH 90 ± 5%). Weight loss in forced air cooling and room cooling was lower than 3-4% with 0.02 ㎜ HDPE film liner treatment during storage. However, it was only below 10% in room cooling without liner treatment and forced air cooling without liner treatment led to the highest weight loss, above 15%. Conversely, the control had lower weight loss than the others. SSC was 2-4°brix for all treatments and there was no difference between postharvest treatments and liner treatments. Color index and firmness both showed no differences with/without 0.02 ㎜ HDPE film and postharvest treatments. In sensory evaluation, forced air cooling with liner treatment was effective, with the highest score, especially in appearance and crispness. After 6 weeks, control kimchi cabbage without liner treatment was damaged seriously in appearance and the internal color had changed to brown. Room cooling and predrying with liner treatment changed the start of internal browning to after 8 weeks storage.

모의 수출 실험을 통한 고랭지 사계성 딸기 ‘Goha’와 ‘Flamenco’의 유통 온도 및 예냉 처리효과

엄향란(Hyang Lan Eum),배상준(Sang Jun Bae),황대근(Dae Keun Hwang),용영록(Young Rog Yeoung),홍세진(Sae Jin Hong) 한국원예학회 2014 원예과학기술지 Vol.32 No.2

This study was conducted to investigate the effects of low temperature shipping condition and precooling treatments (forced a ir a nd r oom cooling) on e verbearing strawberry t hrough e xport simulation o f ‘Goha’ and ‘Flamenco’ c ultivars. After harvest, it took two days to prepare export procedure such as precooling, sorting, storage, transportation, quarantine and handling, and then everbearing strawberry was carried out shipping at room (20-25°C) or low (8°C) temperature conditions. In the case of shipping at room temperature, weight losses of both cultivars were increased up to 10% after 2 days where ‘Goha’ being 2% h igher than t hat of ‘ Flamenco’. In ‘Flamenco’ c ultivar, shipping t emperature a nd p recooling treatment were n ot e ffective in firmness and soluble solids contents during transporting periods. However, in ‘Goha’ cultivar, room cooling treatment and low shipping temperature were effective in maintaining firmness until 4 days after shipping. Especially titratable acidity was affected by shipping temperature (P ≤ 0.001) and precooling treatments (P ≤ 0.05) in ‘Goha’ cultivar. Also shipping temperature under 8°C delayed coloring and decay incidence of both strawberry cultivars, and precooling treatments of both forced air and room cooling reduced frequency of decay. The shelf life of everbearing strawberry at low shipping temperature was extended more than 4 days compared with shipping at room temperature. Precooling treatment including forced air or room cooling will be useful for the two cultivars when they are transported at low temperature. In ‘Flamenco’ cultivar, the effect of forced air and room cooling was similar, whereas in ‘Goha’ room cooling was more effective.

저장 전처리 방법에 따른 배추 ‘춘광’ 품종의 품질변화

엄향란(Hyang Lan Eum),배상준(Sang Jun Bae),김병섭(Byung-Sup Kim),윤정로(Jungro Yoon),김종기(Jongkee Kim),홍세진(Sae Jin Hong) 한국원예학회 2013 원예과학기술지 Vol.31 No.4

Kimchi cabbage ‘Choongwang’ cultivar is mainly cultivated during summer in Gangneung area. ‘Choongwang’ cultivar was harvested in late July, applied with predrying, room cooling, and forced air cooling, and then packaged with/without 0.02 mm HDPE film to estimate the effect of postharvest treatment on quality characteristics (weight loss, trimming loss, firmness, SSC, color index, sensory evaluation) during 8 week storage at 2°C. Kimchi cabbage without 0.02 mm HDPE film showed high weight loss up to 13-20% while those of with liner were significantly lower. Also forced air cooling among the postharvest treatments was effective to reduce both weight loss and trimming loss. Appearance and freshness in sensory evaluation were the important factors in estimating good quality during storage. Liner treatment with forced air cooling showed highly significant for maintaining appearance and freshness (P ≤ 0.01). Color index was no differences between with/without 0.02 mm HDPE film and postharvest treatments. After 6 weeks storage in without 0.02 mm HDPE film with room cooling or control appearance was severely damaged and also internal browning was found. While in with 0.02 mm HDPE film internal browning was found after 8 weeks storage, just in room cooling or predrying treatment.

냉각저장방식에 따른 백미의 냉각 및 저장특성

김의웅 ( Oui Woung Kim ),김훈 ( Hoon Kim ),임태규 ( Tae Gyu Lim ) 한국식품저장유통학회 ( 구 한국농산물저장유통학회 ) 2004 한국식품저장유통학회지 Vol.11 No.4

Design and investigation of a shape memory alloy actuated gripper

S. Krishna Chaitanya,K. Dhanalakshmi 국제구조공학회 2014 Smart Structures and Systems, An International Jou Vol.14 No.4

This paper proposes a new design of shape memory alloy (SMA) wire actuated gripper for open mode operation. SMA can generate smooth muscle movements during actuation which make them potentially good contenders in designing grippers. The principle of the shape memory alloy gripper is to convert the linear displacement of the SMA wire actuator into the angular displacement of the gripping jaw. Steady state analysis is performed to design the wire diameter of the bias spring for a known SMA wire. The gripper is designed to open about an angle of 22.5 when actuated using pulsating electric current from a constant current source. The safe operating power range of the gripper is determined and verified theoretically. Experimental evaluation for the uncontrolled gripper showed a rotation of 19.97. Forced cooling techniques were employed to speed up the cooling process. The gripper is simple and robust in design (single movable jaw), easy to fabricate, low cost, and exhibits wide handling capabilities like longer object handling time and handling wide sizes of objects with minimum utilization of power since power is required only to grasp and release operations.