Performance of the Fast-Ramping High Temperature Superconducting Magnet System for an Active Magnetic Regenerator

Inmyong Park,Chankyeong Lee,Jiho Park,Seokho Kim,Sangkwon Jeong Institute of Electrical and Electronics Engineers 2017 IEEE transactions on applied superconductivity Vol.27 No.4

<P>Fast magnetic field alternation is indispensable for continuous magnetic refrigeration. An active magnetic regenerative refrigerator (AMRR) utilizes magnetocaloric effect of magnetic materials which occurs during magnetization and demagnetization processes. A conduction cooled high temperature superconducting (HTS) magnet can be one of the prospective candidates as an alternating magnetic field generator. This paper describes the development effort of the cryogen-free HTS magnet for the AMRR. The magnet consists of twelve double pancake GdBCO coils which are insulated with polyimide tape. A two-stage GM cryocooler was employed to cool down the magnet. The critical current of the magnet was measured at the operating temperature before alternating current (AC) operation. In order to remove heat produced by AC loss with small temperature difference, thermal links between the cryocooler and the magnet were carefully designed. This paper presents the test results, AC loss analysis of the HTS magnet in the AMRR system. Maximum central magnetic field of 3 T (150 A) was achieved with the maximum ramping rate of 1 T/s (50 A/s). The AC loss was measured as 11.2 W at the operating conditions and the generated heate was effectively removed by the cryocooler. The AC loss was predicted by the numerical simulation and the simulation results were compared with the experimental results.</P>

Development of the active magnetic regenerative refrigerator operating between 77 K and 20 K with the conduction cooled high temperature superconducting magnet

Park, Inmyong,Jeong, Sangkwon Elsevier 2017 Cryogenics Vol.88 No.-

<P><B>Abstract</B></P> <P>The experimental investigation of an active magnetic regenerative refrigerator (AMRR) operating between 77 K and 20 K is discussed in this paper, with detailed energy transfer analysis. A multi-layered active magnetic regenerator (AMR) is used, which consists of four different rare earth intermetallic compounds in the form of irregular powder. Numerical simulation confirms that the AMR can attain its target operating temperature range. Magnetic field alternation throughout the AMR is generated by a high temperature superconducting (HTS) magnet. The HTS magnet is cooled by a two stage Gifford-McMahon (GM) cryocooler. Helium gas was employed as a working fluid and its oscillating flow in the AMR is controlled in accordance with the magnetic field variation. The AMR is divided into two stages and each stage has a different mass flow rate as needed to achieve the desired cooling performance. The temperature variation of the AMR during the experiment is monitored by temperature sensors installed inside the AMR. The experimental results show that the AMRR is capable of achieving no-load temperature of 25.4 K while the warm end temperature is 77 K. The performance of the AMRR is analyzed by observing internal temperature variations at cyclic steady state. Furthermore, numerical estimation of the cooling capacity and the temperature variation of the AMR are examined and compared with the experimental results.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The magnetic refrigerator operating between 77 K and 20 K is fabricated and tested. </LI> <LI> The AMR reached the lowest temperature of 25 K and the temperature span is 52 K. </LI> <LI> The numerical estimation of the performance is compared with the experimental result. </LI> </UL> </P>

Ramping Operation of the Conduction-Cooled High-Temperature Superconducting Magnet for an Active Magnetic Regenerator System

Inmyong Park,Chankyeong Lee,Jiho Park,Seokho Kim,Sangkwon Jeong Institute of Electrical and Electronics Engineers 2016 IEEE transactions on applied superconductivity Vol.26 No.4

<P>An active magnetic regenerator (AMR) system requires fast ramp rate of magnetic field variation. The magnetic field change enables a magnetic refrigerant to create magnetocaloric effect for magnetic refrigeration. In this paper, a conduction-cooled high-temperature superconducting (HTS) magnet has been thermally analyzed and tested for an AMR system. A GdBCO conductor insulated with polyimide tape was wound by dry winding and standard double-pancake coil method. Stycast 2850FT was applied to the edge of the tape conductor so that the cooling plates, which were located at the top and bottom of the coil, should effectively cool the magnet. The whole thermal bridging between the magnet and a two-stage GM cryocooler is analyzed by the numerical simulation and a Joule heating experiment of the HTS magnet at normal state. The inductance of the HTS magnet was measured as 350 mH. The HTS magnet is intended to be operated with maximum 1 T/s at 20 K, cooled by the cryocooler. A solenoid switch and an external dump resistor were employed in order to discharge the HTS magnet. A continuous ramping operation test was conducted with a 60-A peak current and a maximum 20-A/s ramp rate by 3-kW dc power supply. This paper describes the experimental results of the ramping operation of the HTS magnet for an AMR system, and the technical issues on the results are discussed.</P>

Experimental Investigation of Superconducting Linear Compressor (SCLC) for Pulse Tube Refrigerator (PTR)

Jiho Park,Inmyong Park,Jeongmin Cha,Sangkwon Jeong Institute of Electrical and Electronics Engineers 2017 IEEE transactions on applied superconductivity Vol.27 No.4

<P>This research paper focuses on the development of the Stirling-type pulse tube refrigerator (PTR) system. The system includes an innovative cold compression concept by introducing a superconducting linear compressor (SCLC). As one of the key goals of this research, the working gas (helium) is to be compressed directly at cryogenic temperature. The mechanical work (pressure-volume (PV) work) can be directly transmitted to the PTR system without experiencing precooling process. The unique feature of this paper is to utilize a high-temperature superconductor (HTS) coil instead of using metallic conductor coil for a linear motor. By implementing a HTS linear motor to the cold compressor, the ohmic loss can be inherently eliminated, so that the higher motor efficiency can be expected. In this research paper, the experimental validation as a proof of concept is carried out. The HTS linear motor operates at 50 Hz without creating overheat problem. The SCLC stably generates the PV work at the temperature of liquid nitrogen and it is subsequently transmitted to the compression volume of the PTR. The whole PTR system, therefore, can readily operate between 80 and 20 K with the cooling capacity of 0.26 W.</P>

미세 채널에서 R123/R134a/R22 혼합 냉매의 유동 비등 열전달에 대한 실험적 연구

박인명(Inmyong Park),인세환(Sehwan In),정상권(Sangkwon Jeong) 대한설비공학회 2011 대한설비공학회 학술발표대회논문집 Vol.2011 No.7

This paper describes the flow boiling heat transfer of R123/R134a/R22 mixture in a single round micro-channel with 0.19 ㎜ ID. The flow boiling heat transfer coefficients were measured for ternary mixture (R123/R134a/R22 mole fraction: 0.19/0.62/0.19) at various experimental conditions: mass velocities (314, 392, 470 ㎏/㎡-s), heat fluxes (10, 15, 20 ㎾/㎡) and vapor qualities (0.2 - 0.8). The heat transfer characteristics of the R123/R134a /R22 mixture are similar to those of the R123/R134a mixture (mole fraction: 0.5/0.5) observed in the previous flow boiling experiment which indicates that the major heat transfer mechanism in the micro-channel is dominated by evaporation of thin liquid film around the elongated bubbles. The large reduction of heat transfer coefficients compared with pure refrigerant is observed in micro-channel flow boiling by mass transfer effect of mixed refrigerant.

액체 질소 이하 온도에서 작동하는 능동형 자기 재생식 냉각기의 개발

박인명(Inmyong Park),유정현(Junghyun Yoo),정상권(Sangkwon Jeong) 대한설비공학회 2017 대한설비공학회 학술발표대회논문집 Vol.2017 No.6

능동형 자기 재생식 냉동기는 대상을 냉각시키는 데 자성 물질의 자기열량효과를 이용한다. 이 효과는 가역과정이기 때문에 효율적인 측면에서 큰 잠재력을 지니고 있다. 또한 저온에서 기계적인 움직임이 없기 때문에 내구성이 우수한 시스템을 구현할 수 있다. 본 연구에서는 액체질소 온도 이하에서 작동하는 능동형 자기 재생식 냉동기를 구성하였고 성능을 시험하였다. 실험장치는 크게 능동형 자기 재생기, 자기장을 인가하는 고온초전도자석, 작동유체의 질량유량을 발생시키는 왕복유동장치로 구성되어 있다. 재생기의 고온부를 77 K으로 유지시켰을 때 저온부의 온도가 자기열량효과에 의하여 서서히 감소하면서 냉각 되는 것을 확인하였고 최대 45 K의 온도차이를 발생시켰다.

Experimental Investigation on Conduction-Cooled Fast-Ramping Layer-Wound (RE)BCO Superconducting Magnet for Magnetic Refrigeration

Jiho Park,Inmyong Park,Sangkwon Jeong,Seokho Kim IEEE 2015 IEEE transactions on applied superconductivity Vol.25 No.3

<P>Magnetic refrigeration requires a strong magnetic field and its alternation for the magnetization and demagnetization processes. A conduction-cooled (RE)BCO coil was designed and fabricated to exert the maximum central magnetic field of 3.5 T with a field homogeneity of 90% on the magnetic refrigerant bed for an adiabatic demagnetization refrigerator (ADR) operating between 22 and 20 K. The polyimide tape insulated (RE)BCO tape conductor was wound on the stainless steel bobbin with standard layer-wound method whose outer diameter and thickness were 25.4 and 0.3 mm, respectively. The fast-ramping (RE)BCO coil was conductively cooled by a GM cryocooler to approximately 20 K. The (RE)BCO coil winding has a novel thermal drain structure to withstand the high thermal loads during alternating current (AC) operation which consists of high purity copper strip arrays installed between the inter-layers of the coil winding. Alternating magnetic field was stably generated with the peak of 3.0 T at the current of 130 A (10.5 A s<SUP>-1</SUP>). In this paper, the technical issues regarding to the fast-ramping conduction-cooled (RE) BCO coil itself and the integrated operation with the magnetic refrigeration system are discussed.</P>

피스톤이 없는 왕복동식 팽창기의 이론 및 실험적 연구

박세현(Sehyeon Park),박인명(Inmyong Park),정상권(Sangkwon Jeong) 대한설비공학회 2017 대한설비공학회 학술발표대회논문집 Vol.2017 No.6

본 연구는 기존 왕복동식 팽창기에서 내부 피스톤이 제거된 형태의 팽창기에 대한 수치적 모델링과 함께 실험을 진행하였다. 팽창기의 성능을 예측하기 위하여 질량 보존, 에너지 보존 식을 이용하여 수치적 모델을 개발하였고, 직접 실험 장치를 설계하고 제작하여 실험을 진행하였다. 기본적인 수치 해석 모델은 오리피스 밸브(Orifice valve)와 버퍼(Reservoir)가 위상조절기를 구성하는 시스템에 대해 이루어졌다. 팽창기에서 가장 중요한 요소는 팽창 후 배기되어 나가는 기체의 엔탈피이므로 팽창기의 저온부에서 배기되어 나가는 기체의 온도를 예측하고 측정하였다. 고압부와 저압부가 각각 5 Bar, 1 Bar인 경우, 초기 시스템 온도가 약 296.5 K 인 동일한 조건에서 수치해석을 통해 약 277.1 K의 주기적 평형 상태 평균 배기온도를 예측하였으며, 실험적으로는 약 279.8 K의 주기적 평형 상태 평균 배기온도를 기록하였다. 추가적으로 오리피스 밸브를 관성관(Inertance tube)으로 대체하여, 관성관 내부 기체들의 관성 효과를 이용하고자 하였으며, 이에 대한 수치해석 또한 진행하였다.

Development of the closed-loop Joule-Thomson cryoablation device for long area cooling

Cheonkyu Lee,Inmyong Park,Donggyu Yoo,Sangkwon Jeong,Sang Woo Park 한국초전도저온학회 (구 한국초전도저온공학회) 2013 한국초전도저온공학회논문지 Vol.15 No.3