Thermal and structural analysis of a cryogenic conduction cooling system for a HTS NMR magnet

In, Sehwan,Hong, Yong-Ju,Yeom, Hankil,Ko, Junseok,Kim, Hyobong,Park, Seong-Je The Korea Institute of Applied Superconductivity a 2016 한국초전도저온공학회논문지 Vol.18 No.1

The superconducting NMR magnets have used cryogen such as liquid helium for their cooling. The conduction cooling method using cryocoolers, however, makes the cryogenic cooling system for NMR magnets more compact and user-friendly than the cryogen cooling method. This paper describes the thermal and structural analysis of a cryogenic conduction cooling system for a 400 MHz HTS NMR magnet, focusing on the magnet assembly. The highly thermo-conductive cooling plates between HTS double pancake coils are used to transfer the heat generated in coils, namely Joule heating at lap splice joints, to thermal link blocks and finally the cryocooler. The conduction cooling structure of the HTS magnet assembly preliminarily designed is verified by thermal and structural analysis. The orthotropic thermal properties of the HTS coil, thermal contact resistance and radiation heat load are considered in the thermal analysis. The thermal analysis confirms the uniform temperature distribution for the present thermal design of the NMR magnet within 0.2 K. The mechanical stress and the displacement by the electromagnetic force and the thermal contraction are checked to verify structural stability. The structural analysis indicates that the mechanical stress on each component of the magnet is less than its material yield strength and the displacement is acceptable in comparison with the magnet dimension.

Thermal and structural analysis of a cryogenic conduction cooling system for a HTS _MR magnet

Sehwan In,Yong-Ju Hong,Han-Kil Yeom,Junseok Ko,Hyobong Kim,Seong-Je Park 한국초전도.저온공학회 2016 한국초전도저온공학회논문지 Vol.18 No.1

The superconducting NMR magnets have used cryogen such as liquid helium for their cooling. The conduction cooling methodusing cryocoolers, however, makes the cryogenic cooling system for NMR magnets more compact and user-friendly than thecryogen cooling method. This paper describes the thermal and structural analysis of a cryogenic conduction cooling system for a400 MHz HTS NMR magnet, focusing on the magnet assembly. The highly thermo-conductive cooling plates between HTS doublepancake coils are used to transfer the heat generated in coils, namely Joule heating at lap splice joints, to thermal link blocks andfinally the cryocooler. The conduction cooling structure of the HTS magnet assembly preliminarily designed is verified by thermaland structural analysis. The orthotropic thermal properties of the HTS coil, thermal contact resistance and radiation heat load areconsidered in the thermal analysis. The thermal analysis confirms the uniform temperature distribution for the present thermaldesign of the NMR magnet within 0.2 K. The mechanical stress and the displacement by the electromagnetic force and the thermalcontraction are checked to verify structural stability. The structural analysis indicates that the mechanical stress on each componentof the magnet is less than its material yield strength and the displacement is acceptable in comparison with the magnet dimension.

600kJ급 SMES용 전도냉각시스템의 냉각특성 (Ⅰ)

홍용주(Yong-Ju Hong),염한길(Han-Kil Yeom),고득용(Deuk-Yong Koh),김효봉(Hyo-Bong Kim),박성제(Seong-Je Park) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10

SMES systems need cryogenic cooling systems. Conduction cooling system has more effective, compact structure than cryogen. For the effective conduction cooling of the HTS SMES system, the temperature difference between the cryocooler and HTS coil should be minimized. In this study, an experimental study of a conduction cooling system for 600kJ HTS SMES is performed to evaluate the performance of the designed cooling system. Two GM cryocoolers are connected to HTS coil by braided wires, a heat exchanger and cooling plates. In this study, the HTS coil is not attached to the cooling system. To simulate the heat generation of HTS coil, heat load by electric heater is applied to the cooling system. The result shows the cool-down characteristics and temperature variation of the cooling system in the steady state.

전도냉각 고온초전도 SMES 시스템의 기초절연 특성

崔在亨(Jae-Hyeong Choi),郭東洵(Dong-Soon Kwag),千賢權(Hyeon-Gweon Cheon),金相賢(Sang-Hyun Kim) 대한전기학회 2006 전기학회논문지C Vol.55 No.8

Toward the practical applications, on operation of conduction-cooled HTS SMES at temperatures well below 40[K] should be investigated, in order to take advantage of a greater critical current density of HTS and considerably reduce the size and weight of the system. In order to take advantage of a greater critical current density of high temperature superconducting (HTS) and considerably reduce the size and weight of the system, conduction-cooled HTS superconducting magnetic energy storage (SMES) at temperatures well below 40[K] should be investigated. This work focuses on the breakdown and flashover phenomenology of dielectrics exposed in air and/or vacuum for temperatures ranging from room temperature to cryogenic temperature. Firstly, we summarize the insulation factors of the magnet for the conduction cooled HTS SMES. And Secondly a surface flashover as well as volume breakdown in air and/or vacuum with two kind insulators has been investigated. Finally, we will discuss applications for the HTS SMES including aging studies on model coils exposed in vacuum at cryogenic temperature. The commercial application of many conduction-cooled HTS magnets, however, requires refrigeration at temperatures below 40[K], in order to take advantage of a greater critical current density of HTS and reduce considerably the size and weight of the system. The magnet is driven in vacuum condition. The need to reduce the size and weight of the system has led to the consideration of the vacuum as insulating media. We are studying on the insulation factors of the magnet for HTS SMES. And we experiment the spacer configure effect in the dielectric flashover characteristics. From the results, we confirm that our research established basic information in the insulation design of the magnet.

Cool-down characteristic of conduction-cooled superconducting magnet by a cryocooler

Choi, Y.S.,Kim, D.L.,Shin, D.W. North-Holland 2011 Physica. C, Superconductivity Vol.471 No.21

The initial cooling is crucial in conduction-cooled superconducting magnet system. Since a cryocooler is the only heat sink in conduction-cooled superconducting magnet system, the initial cool-down time is strongly dependent upon the refrigeration capacity of cryocooler. In this paper, the process of estimation of initial cool-down time is presented. The procedure includes the modeling of properties of low temperature superconductor, the dimensions of superconducting magnet, the cryogenic loads, the thermal link between magnet and cryocooler, and the available refrigerating capacity of a cryocooler. The method is applied to the 3T superconducting magnet cooled by a two-stage GM cryocooler, showing that the results of proposed method have a good agreement with those of experiment. The effects of superconducting magnet size and secondary thermal link on the cool-down characteristic are also discussed.

전도냉각형 고온초전도 에너지저장장치의 전기적 특성

최재형,곽동순,천현권,김해종,김상현,Choi, Jae-Hyeong,Kwag, Dong-Soon,Cheon, Hyeon-Gweon,Kim, Hae-Jong,Kim, Sang-Hyun 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.2

The conduction-cooled HTS SMES is operated in cryogenic and high vacuum condition. Thus, Insulation design at cryogenic temperature and high vacuum is a key and an important element that should be established to accomplish miniaturization that is a big advantage of HTS SMES. However, the behaviors of insulators for cryogenic conditions in vacuum are virtually unknown. Therefore, we need active research and development of insulation concerning application of the conduction-cooled HTS SMES. Therefore, in this study, we experimented about insulation characteristic high vacuum and cryogenic similar to driving condition of SMES system. Also, investigated about insulation characteristic of suitable some materials to insulator for conduction-cooled HTS SMES. As this results, we possessed basis data for insulation materials selection and insulation design for development of 600 kJ class conduction-cooled HTS SMES.

물질분리를 위한 전도냉각형 초전도자석 시스템 개발

최연석,김동락,이병섭,양형석,정원묵,Choi, Y.S.,Kim, D.L.,Lee, B.S.,Yang, H.S.,Jung, W.M. 한국초전도학회 2008 Progress in superconductivity Vol.10 No.1

A conduction-cooled superconducting magnet system is developed for material separation. The superconducting magnet for material separation has to be designed to have a strong magnetic field in a control volume. Since the magnetic field gradient is larger at the end rather than at the center of the magnet, we developed a design method to optimize the superconducting magnet for material separation. The safety of the superconducting magnet is evaluated, taking into account the electro-magnetic field, heat and structure. The superconducting coil is successfully wound by the wet-winding method. The superconducting coil is installed in a cryostat maintaining high vacuum, and cooled down to approximately 4 K by a two-stage GM cryocooler. The performance of the conduction-cooled superconducting magnet system is discussed with respect to the supplied current, cooling medium and cooling power of a cryocooler.

냉각 방법에 따른 Argyrodite (Li5.5PS4.5Cl1.5)의 구조 및 이온전도성 연구

박상원,이진웅 대한금속·재료학회 2021 대한금속·재료학회지 Vol.59 No.4

All solid-state batteries (ASSBs) are now anticipated to be an ultimate solution to the persistent safety issues of conventional lithium-ion batteries (LIBs). Contemporary society’s expanding power demands and growing energy consumption require energy storage with greater reliability, safety and capacity, which cannot be easily achieved with current state-of-the-art liquid-electrolyte-based LIBs. In contrast, these conditions are expected to be met by implementing ASSBs with high-performance solid-state electrolytes (SSEs). In this work, we altered the microscopic structure and Li diffusional behaviors of argyrodites (Li6- xPS5-xCl1+x), which were precisely monitored with cooling protocols. It was shown that, at the cooling speed of -3 oC·h-1, as the cooling rate decreased, impurities in Li5.5PS4.5Cl1.5 such as LiCl and Li3PO4 gradually diminished and eventually disappeared. At the same time, differences in the lattice sizes of Li5.5PS4.5Cl1.5 crystallites gradually decreased, resulting in a single phase Li5.5PS4.5Cl1.5. It was also found that the Cl content of the 4d crystallographic sites increased, eventually contributing to the improvement in ionic conductivity. This work also revealed the effect of cooling rates on the crystallographic atomic arrangements, which became weaker as a decrease in x. The correlations between ionic conductivities and structural features were experimentally verified via XRD and solid-state NMR studies.

A method for representation and analysis of conformal cooling channels in molds made of functionally graded tool steel/Cu materials

신기훈 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.4

Advances in additive manufacturing technology (AMT) enable the direct fabrication of thermally conductive molds with heat sinks or conformal cooling channels. Although tool steels (e.g., P21, H13, SUS420J2) are popularly used as die materials because of high dimensional stability, tool steels are inefficient for cooling mold dies due to low thermal conductivity. Hence, the adoption of functionally graded tool steel/Cu materials (FGMs) has good potentials for thermally conductive molds to avoid thermal stress concentration while improving thermal conductivity. In this sense, this paper presents a new method for the representation and analysis of conformal cooling channels in molds (injection or blowing) made of functionally graded tool steel/Cu materials. A heterogeneous sweep operation combined with 2D material blending was proposed to construct heterogeneous solid models for conformal cooling channels. In addition, onedimensional P21/Cu FGMs were fabricated using DMT (laser-aided direct metal tooling). Material properties (such as density, specific heat, thermal conductivity, coefficient of thermal expansion, and hardness) were evaluated to obtain more accurate analysis results and to verify the feasibility of such a multi-functional mold. An example is shown to illustrate the entire representation and analysis procedure.

평면충돌제트에 의한 고온 판 냉각과정의 열전달 해석

안대환(Daehwan Ahn),김동식(Dongsik Kim) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.1

Water jet impingement cooling is used to remove heat from high-temperature surfaces such as hot steel plates in the steel manufacturing process (thermo-mechanical cooling process; TMCP). In those processes, uniform cooling is the most critical factor to ensure high strength steel and good quality. In this study, experiments are performed to measure the heat transfer coefficient together with the inverse heat conduction problem (IHCP) analysis for a plate cooled by planar water jet. In the inverse heat transfer analysis, spatial and temporal variations of heat transfer coefficient, with no information regarding its functional form, are determined by employing the conjugate gradient method with an adjoint problem. To estimate the two dimensional distribution of heat transfer coefficient and heat flux for planar waterjet cooling, eight thermo-couple are installed inside the plate. The results show that heat transfer coefficient is approximately uniform in the span-wise direction in the early stage of cooling. In the later stage where the forced-convection effect is important, the heat transfer coefficient becomes larger in the edge region. The surface temperature vs. heat flux characteristics are also investigated for the entire boiling regimes. In addition, the heat transfer rate for the two different plate geometries are compared at the same Reynolds number.