Transactions of the Korean Society of Mechanical Engineers A (대한기계학회논문집A)

The Korean Society of Mechanical Engineers (대한기계학회)
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A Study on the Geometric Design Parameters for Optimization of Cooling Device in the Magnetocardiogram System

심자도 장비의 냉각장치 특성 최적화를 위한 기하 설계 변수 연구

  • Lee, Jung-Hee (BK21 Mechatronics Group, Department of Mechanical Design Engineering, Chungnam Nat'l Univ.) ;
  • Lee, Young-Shin (BK21 Mechatronics Group, Department of Mechanical Design Engineering, Chungnam Nat'l Univ.) ;
  • Lee, Yong-Ho (Korea Research Institute of Standards and Science(KRISS)) ;
  • Lim, Hyun-Kyoon (Korea Research Institute of Standards and Science(KRISS)) ;
  • Lee, Sung-Jin (BK21 Mechatronics Group, Department of Mechanical Design Engineering, Chungnam Nat'l Univ.)
  • 이정희 (충남대학교 기계설계공학과 BK21 메카트로닉스사업단) ;
  • 이영신 (충남대학교 기계설계공학과 BK21 메카트로닉스사업단) ;
  • 이용호 (한국표준과학연구원) ;
  • 임현균 (한국표준과학연구원) ;
  • 이성진 (충남대학교 기계설계공학과 BK21 메카트로닉스사업단)
  • Published : 2010.02.01
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Abstract

A magnetocardiogram (MCG) is a recording of the biomagnetic signals generated by cardiac electrical activity. Biomagnetic instruments are based on superconducting quantum interference devices (SQUIDs). A liquid cryogenic Dewar flask was used to maintain the superconductors in a superconducting state at a very low temperature (4 K). In this study, the temperature distribution characteristics of the liquid helium in the Dewar flask was investigated. The Dewar flask used in this study has a 30 L liquid helium capacity with a hold time of 5 d. The Dewar flask has two thermal shields rated at 150 and 40 K. The temperatures measured at the end of the thermal shield and calculated from the computer model were compared. This study attempted to minimize the heat transfer rate of the cryogenic Dewar flask using an optimization method about the geometric variable to find the characteristics for the design geometric variables in terms of the stress distribution of the Dewar flask. For thermal and optimization analysis of the structure, the finite element method code ANSYS 10 was used. The computer model used for the cryogenic Dewar flask was useful to predict the temperature distribution for the area less affected by the thermal radiation.

인체의 심장 활동에 의해 발생되는 생체 자기 신호를 심자도(magnetocardio-gram, MCG)라고 부른다. 이러한 생체자기장은 극저온 상태에서 고감도 자장센서인 SQUID(Superconducting QUantum Interference Device)를 사용함으로서 측정할 수 있다. 이 심자도 장비의 냉각장치는 액체 헬륨을 냉매로 사용하며 이 냉매를 보관하는 방법이 장비의 성능을 좌우한다. 액체 저온 듀아가 극저온 4 K에서 초전도 특성을 유지하기 위하여 사용된다. 본 연구에서는 액체 헬륨 듀아의 온도분포 특성이 연구되었다. 본 연구에서 사용된 듀아는 액체헬륨 용량이 30 L이고 5일간 유지된다. 듀아에는 150 K와 40 K의 이중 차폐체가 설치되었다. 열차폐체 끝단에서의 온도가 측정되었으며 전산모델의 해석결과와 비교되었다. 기하 설계 변수에 대한 최적화 기법을 적용하여 냉각장치인 저온 듀아의 열전단율을 최소화하였으며 듀아의 응력분포에 영향을 갖는 설계 기하 변수들의 특성을 연구하였다. 냉각장치의 열해석 및 최적화해석을 위해 유한요소 코드 ANSYS 10을 사용하였다. 저온 듀아에 사용된 전산모델은 열복사에 의한 영향을 최소화 할 수 있는 분야에서 온도 분포를 예측하는데 유용하게 사용될 수 있다.

Keywords

References

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