bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical investigation on parameter influence in double-stage Vuilleumier type pulse tube cryocooler (VM-DPTC)
Authors: Wang J , Pan C Z , Xi X T , Chen L B , Zhou Y , Wang J J
Published: June 2020

The double stage Vuilleumier type pulse tube cryocooler (VM-DPTC) is a modified 4 K-class pulse tube cryocooler form the Vuilleumier hybrid pulse tube cryocooler in TIPC, CAS. Besides its compact size and low-frequency working pattern eliminating the moving parts in cryogenic temperature (<77 K) will improve the working stability and reduce the inherited losses. To design a proper double stage pulse tube cryocooler under a certain thermal compressor to work below 5 K, a numerical model based on Sage 10 software was established and the geometry of phase shifter was optimized firstly. Then the influence of working parameters on no-load temperature, cooling power and the heat rejection of the thermal compressor were studied.
Drive force optimization of a pneumatically-driven Gifford-McMahon cryocooler by numerical modeling
Authors: Lei Tian , Zuev Yuri L. , Bao Qian , Xu Mingyao
Published: June 2020

Pneumatically-driven displacer mechanisms are widely used in Gifford-McMahon (G-M) cryocoolers. Particularly for large size G-M cryocoolers, this type of drive is preferable compared to the scotch yoke-type, as only a small motor is required for driving the rotary valve and, therefore, the entire cryocooler can be very compact. Though various numerical models of G-M cryocoolers have been presented in the past, modeling of the pneumatically-driven type and optimization of the driving force have rarely been done. This work presents a one-dimensional numerical model of a pneumatically-driven single stage G-M cryocooler running at 80 K and related studies. The transient model predicts the movement of the displacer and simulates the cryocooler performance simultaneously. An optimization of the drive force is implemented for the defined cryocooler operating at various speeds. It discovers that the driving force reshapes the P-V diagram effectively and has to be well designed according to the frequency to maximize the cooling capacity per mass flow rate.
A Second Law Study of the Regenerators in Cryocoolers based on Pore-level Analysis of Entropy Generation
Authors: Fang Tao , Ghavami Ali , Ghiaasiaan S. Mostafa
Published: June 2020

Regenerators are key components of regenerative cryocoolers and losses in regenerators have a significant effect on the performance of cryocoolers. In previous studies, the efficiency of regenerators has been characterized mostly based on the first law of thermodynamics, and second-law analyses have been based on exergy considerations or irreversibility associated with macroscopic flow models. In this work, we investigate the entropy generation in regenerators based on detailed pore-level simulations. Computational Fluid Dynamics (CFD) simulations are used to model two-dimensional regenerator geometries, and examine the microscopic flow and heat transfer phenomena that cause irreversibility. A CFD approach and a volume averaging semi-analytical approach are developed to analyze the entropy generation in pore level. A modified Bejan number (Re
conv) and a Performance Evaluation Factor (PEF) are propose as indicators for the level of entropy generation in regenerators. The predicted entropy generation rates at various Reynolds numbers and geometric dimensions are analyzed. The results indicate that the proposed semi-analytical approach can be a convenient alternative to CFD simulations when empirical data of convective heat transfer and friction factor are available. The analysis of entropy generation using Reconv
and PEF can be used to minimized the irreversibility of regenerators.
An experimental investigation on parallel-plate finned heat exchanger working with cryogenic oscillating helium flow
Authors: Huang J L , Jin T
Published: June 2020

The space-cycle averaged Nusselt number is used to characterize the heat transfer characteristics of cold end heat exchanger in cryocoolers working with cryogenic oscillating helium flow. An experimental setup for cryogenic oscillating flow heat transfer measurement was designed and established. According to the experimental data obtained, it is evident that low temperature is significantly disadvantageous for heat transfer in oscillating flow. Similar to the experimental results at room temperature, under different mass flow rates, the heat exchanger has its own corresponding optimal Reynolds number at certain temperature for maximized heat transfer capacity.
Helium Transfer Line with Conduction-Cooled Nb-Ti Superconducting Wires for COMET Muon Transport Solenoid
Authors: Okamura Takahiro , Yoshida Makoto , Oonaka Masaya , Ohhata Hirokatsu , Ki Taekyung , Makida Yasuhiro , Sasaki Ken-ichi , Iida Masahisa , Tateno Akiko , Matsuo Masahiro , Aoki Itsuo
Published: June 2020

Cryogenic system of the superconducting magnet for COMET (COherent Muon to Electron Transition) experiments has been constructed in the J-PARC since FY2013. The cryogenic system can be roughly divided into superconducting magnet, refrigerator system and inter-connect system. The refrigeration system is composed of cold box and warm screw compressor system which are located on the surface. On the contrary, magnet system will be installed in the underground. Therefore the inter-connect system is mainly composed of current lead box and transfer line, which are regarded as a system for connecting between ground facility and the underground superconducting system. Since the superconducting magnet is cooled by two-phase flow helium at around 4.5 K, the transfer line has an adiabatic structure with shield line of around 50 K. In addition, conduction cooled superconducting cables are laid in parallel with the two-phase flow cooling line. In this study, simulation on the pressure drop of gas-liquid two-phase flow of helium is introduced to determine the cooling pipe diameters in the transfer line. Then the detail structures of the transfer line and cooling scheme of the superconducting cables optimized by several experiments will be presented.
The CFD study of three-dimensional model of porous medium regenerator with oscillating flow
Authors: Chi CY , Mou J , Lin M Q , Hong GT , Chen HL
Published: June 2020

The regenerator is the core heat exchange component of the Stirling engine. The performance of it is determined by the configurations and physical properties of the filling material. In this paper, a three-dimensional model of the regenerator filled with powder sintered material is established and simulated with the oscillating flow using ANSYS. After specific post-processing, the relationship between Reynolds number and specific friction coefficient as well as Nusselt number is numerically solved which provides a method to acquire characteristics of flow resistance and heat transfer for the specific configuration. Finally, the parameter of

Nu
/

C
f

1
/
3

is chosen as an indicator to evaluate the performance of the four fillers, and the potential of being a future regenerator filler is discussed.
Entropy generation in the woven mesh regenerator filler of cryocoolers
Authors: Ghavami Ali , Fang Tao , Ghiaasiaan S Mostafa
Published: June 2020

The regenerator is a key component of a pulse tube cryocooler, and is also a major contributor to irreversibility and losses in the cryocooler. In this study a method for the assessment of losses in cryocooler regenerators based on entropy generation is proposed. Pore-level CFD simulations are performed for woven mesh regenerator filler by defining periodically repeating unit cells. Simulations are performed for steady-state (uni-directional) as well as periodic flows. It is shown that entropy generation in periodic flow is higher than in steady flow, and is sensitive to operating parameters as well as small geometric irregularities. It is proposed that by optimization of the microstructure of regenerator fillers the entropy generation and losses can be minimized.
Transient Conjugate Heat Transfer Numerical Simulation in Superfluid Helium
Authors: Vitrano A , Bruce R , Baudouy B
Published: June 2020

Computational simulations of superfluid helium are needed in order to improve the cooling system design of superconducting magnets in particle accelerators and to achieve a better understanding of the transient phenomena during magnet quenches. A conjugate heat transfer numerical model based on the C++ toolbox OpenFOAM [1] is implemented to three-dimensional case studies involving superfluid helium and heating sources. The governing equations of the solver are modified according to the Kitamura’s model [2], a simplified version of the two-fluid model developed by Khalatnikov [3]. This simplified model is based on the assumption that the thermo-mechanical effect term and the Gorter-Mellink mutual friction term prevail on the others in the superfluid component momentum equation. Simulations are performed with the thermal conductivity function of superfluid helium both from theory [4] and the formulation used by Sato [5], who normalized the function according to a different conductive heat flux exponential coefficient determined from data analysis. An empirical calculation of the Kapitza conductance [6] is adopted in order to simulate the thermal resistance at the interface between helium and solids. Steady-state and transient simulations are compared to experimental data available in the literature. For such purpose, data are used from Van Sciver’s experiment in a helical coil [7] and a rectangular cross-section channel experiment conducted at CEA Paris-Saclay. The experiments comprised heaters and multiple temperature probes situated at different locations to track the temperature distribution and evolution of the superfluid helium state.
Thermodynamic and economic aspects of the Nelium Turbo-Brayton refrigerator development for the FCC-hh
Authors: Savelyeva S , Klöppel S , Haberstroh C , Quack H
Published: June 2020

Within the conceptual design study for the Future Circular Hadron Collider (FCC-hh) it was shown, that a large part of the total cryogenic heat load falls into the temperature range between 40 to 60 K. Thus, additional cryogenic refrigerators for this temperature level are specified for each of the 10 foreseen cryoplants. Such a cryogenic system was developed at the TU Dresden and is based on a Brayton cycle working with a neon-helium mixture as refrigerant and using multistage centrifugal compressors. The duty requirements comprise a 6.2 MW total heat load at 40 to 60 K for beam screens and shielding, additional 2.7 MW at 300 to 40 K for the pre-cooling of the helium cycle and a turndown ratio of up to 3.8. The optimisation of the referenced system was performed in order to obtain a high efficiency of the cryogenic cycle and tolerable costs for system components at the same time. An analysis of the mixture composition influence on the components and on the total gas mass was performed. Restrictions for industrially existing hardware were taken into consideration. Updated cycle parameters are subsequently described.
Dynamic simulations of medium-sized hydrogen liquefiers based on EcosimPro simulation software
Authors: Li J , Liu L Q , Xiong L Y , Peng N , Li K R , Ke C L
Published: June 2020

Dynamic simulations of medium-sized hydrogen liquefiers have been performed using process simulation software EcosimPro. Two hydrogen liquefier process flows have been simulated. One process flow is a helium refrigerator with one helium turbine providing cooling power for hydrogen liquefier, the other one is a helium refrigerator with two helium turbines providing cooling power for hydrogen liquefier. Control logics and control strategies for these two hydrogen liquefiers have been proposed. The cooling down simulations have been performed separately. One turbine hydrogen liquefier, pressure ratio is 2/16 bara, helium mass flow rate is 111 g/s, hydrogen mass flow rate is 4.3 g/s, the liquefaction rate of hydrogen is about 191 L/h. Two turbines hydrogen liquefier, pressure ratio is 1/14 bara, helium mass flow rate is 110 g/s, hydrogen mass flow rate is 5.2 g/s, the liquefaction rate of hydrogen is about 184 L/h. Comparison and discussion have been proposed.
Improvement of Cryogenic System for China Spallation Neutron Source
Authors: Bin Ye , Chongchao He , Meiying Ding , Yu Zhang , Yaqiong Wang , Na Li , Kun He
Published: June 2020

The commissioning of China Spallation Neutron Source(CSNS) cryogenic system was completed in July, 2017. It runs 258 days totally until July, 2018, and the longest continuous running period is 184 days. CSNS had passed the national acceptance in August 2018. Now it is running stable from September 19th 2018. There are no any faults in the process of running. However, cryogenic system needs to be improved in the near future. The flow of hydrogen cycle can’t be controlled effectively. The flows through the cryogenic circulators working at the same frequency are different. The pressure drop of the ortho-para convertor is very high, and it maybe the root cause of this phenomenon. Therefore, the ortho-para convertor needs to be redesigned and re-manufactured, and the flow resistance must be measured. In future, the new ortho-para convertor will be installed in hydrogen cold-box.
The dynamic synthesis time-lag control for the 1.3 GHz LCLS-II Cryomodule test at Fermilab
Authors: Pei Liujin , Hansen Ben , Theilacker Jay , Pei Qing
Published: June 2020

The 1.3GHz LCLS-II Cryomodule (CM) has 8 cavities and each cavity has 9 RF cells and 80W heater. The 1.3GHz LCLS-II CM is 12.2-meter-long and contains a total 241.3 liters (equivalent liquid) of liquid helium, which is filling up by the 4KW@2.0K cryogenic plant at the Fermilab Cryomodule Test Facility (CMTF). The dynamic synthesis 2K cryogenic control system is built to control the long time-lag, unstable CM cryogenic system, under different modes operations. A report on the results obtained from the dynamic synthesis long time-lag control in the CMTF 1.3GHz CM test will be presented.
Model Predictive Control for Helium Compression Station: Simulation and experimental Results
Authors: Pham X.H. , Bonne F. , Alamir M. , Bonnay P. , Attard A.
Published: June 2020

This paper deals with multivariable on-line model predictive control (MPC) for helium Warm Compression Stations (WCS). During WCS operation, control algorithms must ensure that the operational constraints are respected. These constraints can be imposed by the system itself (valves open from 0 to 100%, compressor maximum electrical current and pressures, …), or imposed by the users (valves which must remain closed or open to a minimum other than 0, pressures which should not be too low or too high). The MPC controller takes into account the constraints and set points into one optimization problem, which makes it the ideal candidate to control the WCS. The papers presents experimental results obtained on the SBT WCS, showing that the WCS is running safely while taking into account the constraints. The experimental tests shows that using MPC leads to high stability and fast disturbance rejection such as those induced by a turbine or a compressor stop, which is a key-aspect in the case of large-scale cryogenic refrigeration. The proposed control scheme can be used to achieve precise control of pressures in normal operation or to avoid reaching a stopping criteria (such as excessive pressures) under high disturbances (such as the pulsed heat load expected to take place in future fusion reactors).
Simcryogenics: a Library to Simulate and Optimize Cryoplant and Cryodistribution Dynamics
Authors: Bonne F. , Varin S. , Vassal A. , Bonnay P. , Hoa C. , Millet F. , Poncet J.-M.
Published: June 2020

In many fields of engineering, conception and operation teams need to perform simulations in order to design systems fulfilling the user requirements and to operate the systems efficiently. To simulate a cryogenic plant and its distribution to the end-users, a large number of commercial or homemade tools are nowadays available. However, there is a lack of available solutions for rapid dynamic simulations either for control with model-based design and for design optimization through parametric studies. This article presents the Simcryogenics library that has been developed at the CEA Cryogenic Engineering Department for several years. This library aims at generating model-based control schemes for cryogenic plants that are subject to high disturbances (such as the pulsed heat loads in fusion reactors or particle accelerators). The library is based on Simscape, the modelling language extension of the Matlab/Simulink software suite, which is very flexible and well documented. This paper introduces how Simcryogenics works, how to use it as well as it provides examples of applications such as the modelling of warm compression stations and cold boxes, the simulation of the cooling of superconducting magnets and RF cavities, the generation of control schemes.
HECAL: A cryostat for calibration of hot wires
Authors: Kharche S , Moro J P , Baudet C , Girard A
Published: June 2020

The Laboratory SBT (“Systemes à Basse Température”) has studied Fundamental Turbulence at High Reynolds Numbers for many years. Different experiments were performed, which allowed to study high Reynolds Number flows, and also to compare these (normal helium) turbulent flows with superfluid flows driven under the same conditions. First section describes the interest of hot wire anemometry to characterize the turbulent flows. Hot wires were used already in Hejet, and more recently in SHREK. However, the hot wires should be calibrated, which is not always possible in situ. Therefore, we built a facility dedicated to the test and calibration of hot wires. This original facility is described in second section; instead of having a fixed hot wire in an incoming flow, which is the usual situation for hot wire calibration devices, the hot wire to calibrate is installed on a support part, which can be rotated in a fluid at rest. In order to calibrate the hot wires in the same velocity domain as in the SHREK and Hejet experiments, the support of the hot wire can reach velocities of a few meters per second. The first results obtained with Hecal are presented in third section. Fourth section describes the future work to be performed in the CEA facilities.
Design optimization and calibration of a void fraction measurement capacitance sensor for LN2 flow
Authors: Nagendra H N , Verma R , Sagar P , Akber K , Kasthurirengan S , Shivaprakash N C , Sahu A K , Behera U
Published: June 2020

Cryogenic fluids are used for wide range of industrial and laboratory applications. Vacuum or super-insulated transfer lines are efficiently used to transfer these fluids from the storage Dewars to the end applications. As the heat transfer to the cryogens flowing through the transfer line cannot be completely eliminated, many a times two-phase flow occurs during the transfer process. It is necessary to estimate the quality of the flow (void fraction) and the amount of cryogen being evaporated in the transfer process. Many techniques are available to measure the void fraction, but implementing these techniques to cryogenic fluid flow is sometimes difficult and expensive. Capacitance measurement is easy and simple method to find the liquid level and void fraction. Towards this, an attempt has been made to design void fraction measurement sensor based on capacitance measurement. Most of the capacitance sensors are made with inner glass tube, which needs special attention in handling the device and also it is difficult to make the end connections for the glass tubes. The present work deals with the design optimization of Hylam™ (Bakelite) and fibre-reinforced plastic (FRP) inner tube concave plate capacitance sensors for liquid nitrogen level measurement. 3-D modelling and thermo structural analysis of the developed sensors has been carried out in ANSYS workbench and electrostatic analysis has been carried out using ANSYS Maxwell software. The results obtained by the analysis have been validated with experimental results.
Preliminary conceptual design of FCC-hh cryo-refrigerators: Air Liquide Study
Authors: Tavian L , Millet F , Roig M , Zick G , Bernhardt JM
Published: June 2020

In the framework of a world-wide international collaboration, the FCC-hh, a 100 TeV hadron collider in a 100-km long tunnel, is proposed as a future circular collider beyond LHC at CERN offering the broadest discovery potential at the energy frontier. For such high performance hadron collider, the cryogenic system has to distribute very large cooling capacities all along the 100-km tunnel for the superconducting magnets continuously cooled at 1.9 K and for the beam screens operated between 40 and 60 K. The required total cooling power will be produced in 10 refrigeration plants with a unit equivalent capacity of 100 kW at 4.5 K, up to 4 times larger than the present state-of-the-art. Half of the entropic refrigeration load is due to the synchrotron radiation produced by the high-energy proton beams and deposited on beam screens actively cooled around 50 K. This non-conventional thermal load distribution is an additional challenge for the FCC-hh cryogenic system. Furthermore, the cryogenic system has to cool down the cold mass of the FCC-hh machine in less than 20 days with controlled thermal gradients in the cryo-magnets and beam screens. Based on preliminary design works from research institutes, an engineering study was performed with world-leader industries to assess a preliminary conceptual design for the FCC-hh cryogenic plants with industrial solutions and innovative technologies. The present paper recalls the FCC-hh cryogenic requirements and presents the main results of Air Liquide study confirming the novel precooling refrigeration option down to 40 K.
Experiences during Design, Fabrication, Assembly and Factory Acceptance Test of the ITER Cryoplant Termination Cold Box
Authors: Patel P , Vaghela H , Muralidhara S , Shukla V , Garg A , Das J , Dash B , Madeenavalli S , Chang H-S , Grillot D , Sarkar B , Cursan M , Oppolzer K , Sander F , Adler E
Published: June 2020

The ITER Cryodistribution (CD) system distributes cryogenic power from the cryoplant to the applications, namely superconducting magnets, cryopumps, etc. The ITER CD system comprises seven cold boxes of which the Cryoplant Termination Cold Box (CTCB) is the largest one. The CTCB plays a pivotal role in distributing the cold helium fluid with the highest mass flow rates of 4 kg/s coming from one of the 80 K plants to the applications. The physical connection between the CTCB and different applications is through nine cryolines (CLs) having diameters ranging from 0.45 m to 1.0 m. The CTCB has been manufactured and assembled with various large size components such as electrical heater system of 600 kW capacity, cryogenic control valves of size DN200, bubble panel thermal shield (TS) made of stainless steel, etc. The CTCB, which withstands interface loads of ∼1.4 times of its own weight, has been analysed for its functional and thermo-structural requirements under various load conditions. Components & subsystems were manufactured and factory tested individually in various locations in Europe and India to be finally assembled in one place. The CTCB has also been integrally tested, of which major activities were the pressure and helium leak tightness tests, followed by functionality checks of all instruments. The present paper describes the challenges involved and how they were resolved as well as lesson learnt during the design, fabrication, assembly, and factory acceptance test (FAT) phase of the CTCB project.
Cryogenic design of FRIB cryomodule and distribution system and the present status
Authors: Ganni V , Knudsen P , Casagrande F , Jones S
Published: June 2020

The Michigan State University (MSU) Facility for Rare Isotope Beams (FRIB) accelerator utilizes six types of cryo-modules that are being installed in three Linac segments in the FRIB tunnel. The cryomodules contain both superconducting RF cavities and solenoid magnets with 2 K and 4.5 K refrigeration loads (respectively), magnet lead flow loads and 35-55 K shield loads and power coupler intercept loads. The first Linac segment (LS-1) with fifteen cryomodules was commissioned at 4.5 K and at 2 K. Commissioning experiences and some salient features of the cryogenic design of the cryomodules and the helium distribution systems will be discussed.
FRIB cryogenic control system
Authors: Joseph N , Vargas G , Stanley S , Dudley C , Thrush M , Strong H , Knudsen P , Ganni V , Casagrande F
Published: June 2020

The cryogenic system at the Facility for Rare Isotope Beams (FRIB) supports loads for 2 K refrigeration, 4.5 K refrigeration and liquefaction, and a 35-55 K thermal shield for the linear accelerator consisting of 46 cryomodules, 4 superconducting dipoles and 14 superconducting magnets for the experimental system. The controls system for cryogenics was designed, installed, and commissioned with the goal of high availability, ease of maintenance, and simplicity of operation. The personnel protection system (PPS) is a separate system which monitors for oxygen deficiency hazards (ODH) throughout the cryo-plant and around the cryogenic loads. The system consists of Allen-Bradley programmable logic controllers (PLCs) with local human machine interfaces (HMIs) along with the Experimental Physics and Industrial Controls System (EPICS) for normal operations and data acquisition. Two separate networks are utilized in the cryogenic facility. One is a network cluster that houses EPICS. It is designed with high redundancy and is completely separate from the network used for the rest of the particle accelerator. The second network only includes PLCs and HMIs for faster data transfer between PLCs, increased flexibility for changing operating conditions, and complete system operation in the case of an EPICS network failure. This paper reports on the design choices selected and experiences in integrating and commissioning the FRIB cryogenic control system.
Cryogenic operational experience from the LHC physics run2 (2015 – 2018 inclusive)
Authors: Brodzinski K , Bradu B , Delprat L , Ferlin G
Published: June 2020

With end of year 2018 the LHC has completed its second physics run and started its second two-years long shut down period dedicated to planned consolidation, maintenance and upgrade activities. The run2 – four-year physics operation period started in spring 2015 – was used mainly for luminosity production but also to allow the optimization and adaptability of the cryogenic system capacity to compensate for generated operational heat loads. Several tests and qualifications were studied and applied to the configuration of the available equipment in order to reach a deep understanding of the real operation limits. Dedicated global improvements were implemented in the control system, especially in regards of handling the beam induced dynamic heat load during transitory operational states. Adequate modifications were also applied for the Inner Triplet magnets control system to compensate for dynamic heat load related to secondaries, close to the interaction points of the ATLAS and CMS detectors. This paper will give a general overview of the LHC cryogenics operation with specific information on encountered operational difficulties and applied solutions on the system. Helium inventory management, including process use and leaks, as well as the system overall availability indicators will be presented.
Cryogenic management of the LHC run 2 dynamic heat loads
Authors: Bradu B , Brodzinski K , Ferlin G
Published: June 2020

During the LHC (Large Hadron Collider) Run 2 between 2015 and 2018 inclusive, significant dynamic heat loads have been generated and successfully managed by the LHC cryogenic system. These dynamic heat loads are generated by several physical phenomena occurring at two temperature levels and with different time constants. On the magnet cold-mass maintained at 1.9 K, dynamic heat loads are coming from eddy currents generated during the magnet transients, resistive heating in welds of superconducting electrical circuits, beam gas scattering, beam losses, and secondary particles escaping from collisions (debris). On the beam screens, actively cooled between 4.6 K and 20 K, the circulating beams produce also dynamic heat loads due to synchrotron radiations, image current and photo-electron clouds. This paper presents the measurements inventory performed during the Run 2 to assess these dynamic heat loads as a function of the different accelerator parameters (beam energy, beam intensity, injection scheme, etc.). Then, the related compensation measures and adapted cryogenic operation modes applied to manage the induced transients at the different time scales will be presented.
Design status of the ESS cryogenic moderator system
Authors: Tatsumoto H , Lyngh D , Beßler Y , Klaus M , Hanusch F , Arnold P , Quack H
Published: June 2020

The Cryogenic Moderator System (CMS) has been designed to cool high-energy neutrons down to cold neutrons in two cryogenic hydrogen moderators (four ones in the future) by forced flow of subcooled liquid hydrogen at 17 K and 1.0 MPa. At 5 MW proton beam power, an estimated nuclear heating of 6.7 kW (17.3 kW in the future) is generated in the moderators. The subcooled liquid hydrogen is circulated by two pumps arranged in series with a mass flow rate of 1 kg/s to maintain the average temperature rise over each moderator below 3 K and is cooled through a plate fin heat exchanger by a helium refrigerator with a cooling capacity of 30.3 kW at 15 K. The ESS moderator vessels are optimized for maximum cold neutron brightness and pure para-hydrogen, requiring a para concentration of > 99.5 %. An ortho-para-hydrogen convertor is integrated into the loop along with an online para-hydrogen measurement system. The pressure fluctuation caused by unpredictable abrupt changes of nuclear heating will be mitigated using a pressure control buffer with a volume of 65 1.
Experimental Investigations on Cold Recovery Efficiency of Packed-bed in Cryogenic Energy Storage System
Authors: Dutta Rohan , Sandilya Pavitra
Published: June 2020

Cryogenic Energy Storage (CES) system has large power generation capability, and comparable cost with respect to the non-cryogenic technologies (pumped-hydro, compressed air energy storage systems). This is not location specific unlike the non-cryogenic energy storage systems and also is environment friendly. High-energy requirement for liquefaction process in the CES system, however, leads to low turnaround efficiency of the system. Efforts have been made to reduce the specific work-requirement in the liquefaction process by thermal energy storage at temperature around 150 K as available during power generation stage of the system. One of the methods of storing the thermal energy at such low temperature is using packed-bed of pebbles. A few studies have been reported in the available literature indicating a reduction in storage efficiency during continuous operation of such packed-beds leading to reduction in turnaround efficiency of the CES system. In this paper, experimental findings for better insight into the packed-bed behavior are reported. An experimental setup of packed-bed thermal energy storage using rock pebbles as bed material was used for this purpose. Temperatures along the axial direction inside the bed were measured and the results were analyzed and the storage efficiencies during full-load and part-load of operations were determined.
Development of zero boil-off cooling systems for superconducting self-shielded MEG
Authors: Narasaki K , Tsunematsu S
Published: June 2020

A mobile Magneto encephalography (MEG) of Sumitomo Heavy Industries, Ltd. (SHI) uses a high temperature superconducting magnetic shield (HTSMS), Superconductor-Normal-metal-Superconductor (SNS) type Superconducting Quantum Interface Device (SQUID) sensors, and they are cooled by a zero boil-off cooling system. The zero boil-off cooling system consists of a circulating cooled helium gas system for cooling the HTSMS below temperature 90 K and a helium recovery system for cooling the SNS type SQUID sensors to liquid helium temperature. The zero boil-off cooling system are designed to allow measurement in an operating state, allowing arbitrarily long usage. We succeeded first measurement of neuron current in brain by using SHI’s MEG with Helium zero-boil off cooling system at April, 2018. This paper describes overview of SHI’s MEG, the thermal design of the zero boil-off cooling system for our MEG and the results of cooling tests.
The modelling and design of an MRI-compatible cryosurgical probe
Authors: Kossel L , Pfotenhauer J , Harter R
Published: June 2020

Cryo-ablation is a breast cancer treatment method that utilizes a small probe in precise locations within the body to freeze and destroy unwanted cancer tissue. Recently, there has been a growing interest in combining cryo-ablation with magnetic resonance imaging (MRI). The challenge of combining these two technologies is that MRI devices require the absence of metals, and traditional heat exchangers used in cryoprobes are typically composed of thermally conductive metals that tend to disrupt the image produced by an MRI, impairing its functionality. Subsequently, it becomes of interest to develop a heat exchanger composed of thermally conductive MRI-compatible materials such as zirconium. This report presents the results of a thermal modelling effort to characterize and design a non-metallic Joule-Thomson cryoprobe for cryo-ablation. The model is comprised of a Joule-Thomson valve, as well as a discretized recuperative heat exchanger that includes the effects of axial conduction, pressure drop, two-phase and single-phase convection correlations, and fluid properties for single-components and mixtures. The device operates at 170 K with a heat load of 10 W, which is a viable temperature and heat load for cryo-ablation.
A study of thermal performance change of cryogenic heat pipes by wick structures for wide range of working fluid filling ratio
Authors: Wanison R , Kimura N , Murakami M
Published: June 2020

In this research the performances of nitrogen cryogenic heat pipes with different wick structures were compared under the condition of a wide range of heat load and several filling ratios. The heat pipes tested are commercially available ones, which were originally designed for room temperature applications using water as a working fluid. For the present research, working fluid, water, was replaced by liquid nitrogen. Heat pipe samples with three types of wicks, namely, axial grooves (G), sintered metal (S), and the combination of them (SG), were tested for comparing the thermal performance of the heat pipes with different wick structures, which is characterized by the effective thermal resistance Rth
. The experimental data of the maximum heat transport capability Qmax
was compared with theoretical predictions on the basis of the capillary limit for each wick structure. Under high filling ratio condition, wide range of heat load was supplied to investigate the variation of the thermal resistance including such operations as dry-out state and the state where liquid puddle was formed in the pipe. The result indicates that the thermal performances of heat pipes with three kinds of wick structures are ordered as follows in descending order; SG, S and G wick.
Design and experimental research of the cryogenic ejector to inject liquid nitrogen
Authors: Jia Q M , Li Z Y , Gong L H , Liu L Q , Zhu W P , Zhang M M , Su H K
Published: June 2020

With the development of cryogenics, the demand of cryogenic liquid increases constantly. However, there are some difficulties to control and to adjust the extraction of cryogenic liquid especially for liquid helium. Compared with the immersed pump, the ejector has huge advantages in pumping the cryogenic liquid from cryogenic Dewar, like stable operation and simple structure. Considering the similarity between liquid nitrogen and liquid helium and the high cost to conduct the liquid helium experiment, this paper reports a research on the cryogenic ejector in the nitrogen temperature range. The experiment platform customized for liquid nitrogen was set up and the experiment of injection was launched. The nitrogen gas, as the primary flow accelerating in the nozzle, injects the liquid nitrogen at the outlet of nozzle. Two flows blend in the mixing chamber and flow out from the diffuser. Based on the ideal gas assumption and energy conservation, the sound velocity can be derived from two kinds of equations, obtaining the critical condition of primary flow thermal properties. Depending on the properties and previous research experience, the structure of ejector is designed and established, which could effectively inject liquid nitrogen from the cryogenic liquid cylinder. The problems and challenges are analyzed. In conclusion, this paper introduces the design method of cryogenic ejector and builds a liquid nitrogen test instrument. This method makes the extraction of cryogenic liquid more convenient, which is of universal significance for the cryogenic research work.
Molecular simulation on adsorption of helium by activated carbon in 4-10 K
Authors: Xi X T , Wang J , Chen L B , Zhou Y , Wang J J
Published: June 2020

In the liquid helium temperature region, the specific heat of helium increases rapidly, so adsorption behavior of helium on activated carbon is expected to be used in the regenerator of 4-K class cryocoolers to improve the performance of the refrigerator. In this paper, we use Grand Canonical Monte Carlo method to simulate the adsorption of helium on the amorphous carbon in 4-10 K. And the structural parameters of amorphous carbons and the effect of temperature, pressure, graphite slice’s size and density of amorphous carbon on the adsorption amount were analyzed. The results show that the amorphous carbon constructed from the larger size graphite slice has a smaller specific surface area and a larger pore volume. And as the temperature decreases and the pressure increases, the amount of adsorbed helium increases. In addition, we have found that mixed-filled amorphous carbon can obtain higher specific surface area and pore volume, and has better comprehensive properties.
Failure modes, effects and criticality analysis of a 3kW@4.5K helium refrigerator
Authors: Zong Y W , Zhou Z W , Zhang Q Y , Zhu Z G , Yang P C , Hu B
Published: June 2020

The comprehensive research facility for key systems of fusion reactors was included in the “13th Five-Year Plan” priority project in China. In order to meet the requirements of cryogenic testing of large superconducting magnets, it is proposed to build a 3kW@4.5K refrigerator and carry out research on 3kW@4.5K superfluid helium cryogenic system. In order to evaluate the reliability of the 3kW refrigerator, the FMECA analysis was performed on the helium refrigerator. The refrigerator system is divided into three subsystems: the compressor system, the monitoring and control system and the cold box, to identify the failure mode and the impact on the refrigerator system related functions. The critical value is calculated and the critical matrix is drawn by the severity and the occurrence of the rating criteria. Identify the parts with high and medium risks and propose corresponding risk mitigation measures.
Analysis of freezing risk during LNG evaporation process
Authors: Brenk Arkadiusz , Rogala Zbigniew , Malecha Ziemowit
Published: June 2020

Liquid natural gas (LNG) boiling process concerns majority of LNG applications because of a need of its regasification. Depending on pressure an equilibrium temperature of LNG is 112-160K. The low boiling temperature of LNG makes the vaporisation process complicated. An important risk of the regasification is related to a possibility of a solid phase formation (freezing of a heating fluid). For a range of important applications the heating fluid is water or water-glycol mixture, characterized by freezing temperature considerably higher than the boiling temperature of LNG. The solid phase formation can lead to an increase of hydraulic pressures losses, deterioration of the heat transfer or even to the destruction of a heat exchanger and any accompanying device. It motivates a need for better understanding and control of a heat transfer related to the regasification to avoid the solid phase formation. The current work analyses a LNG regasification and a risk of solidification in a generalized shell and tube heat exchanger. The conducted study helped to define a critical Reynolds number below which the solidified ice totally blocks the flow.
Electrical Tree Aging of Epoxy-Based Nanocomposites at Cryogenic Temperature
Authors: Wang Yongguang , Huang Rongjin , Huang Chuanjun , Wu Zhixiong , Dong Hongyu , Shen Fuzhi , Zhang Kaikai , Li Xu , Li Laifeng
Published: June 2020

Electrical insulation at cryogenic temperatures is a key technology in the development of superconducting cables and superconducting current limiters. Due to their improved electrical, mechanical and thermal properties, the application of epoxy nanocomposites in high voltage power systems has shown a broad outlook. In this paper, tests were conducted to investigate the electrical tree aging phenomenon in epoxy resin/Al2O3 nanocomposites in liquid nitrogen under AC voltages. The test samples were prepared with six levels of nanofiller content: 0 wt %, 1 wt %, 2 wt %, 3 wt %, 4 wt %, and 5 wt % by weight ratio. Experimental results showed that nano-fillers below 3% are easy to cause the electric field distortion at the needle tip, which reduces the tree inception voltage in the composite sample compared to that in the neat epoxy sample. At low temperature, the effect of electric field distortion on the tree inception voltage is significantly weakened and the tree growth rate decreases sharply with the increase of the content of the nano-filler.
Thermal Analysis of a Superconducting Undulator Cryostat for the APS Upgrade
Authors: Shiroyanagi Y , Anliker E , Hasse Q , Ivanyushenkov Y , Kasa M , Fuerst J
Published: June 2020

The Advanced Photon Source Upgrade includes four 4.8-m-long superconducting undulator (SCU) cryostats, each containing two planar undulator NbTi magnets up to 1.9 m long. The cooling is provided by six cryocoolers arranged in three thermal circuits. The magnets are indirectly cooled with LHe penetrating through channels in the magnet cores. This 4 K circuit, which also includes a LHe tank, is cooled by five 4 K cryocooler 2nd stages. A beam vacuum, which is thermally isolated from the magnets, is cooled by one 10 K cryocooler 2nd stage. A thermal shield and warm parts of current leads are cooled by the 1st stages of all six cryocoolers. This paper presents an ANSYS-based thermal analysis of the new SCU cryostat including all thermal circuits. The benchmarked thermal conductance between the cryocooler cold heads and the LHe tank are used in the calculations as well as the measured cryocooler load lines. The model predicts temperatures in the system, total 4 K heat loads, and excess cooling power for various operational modes of the undulator.
Thermo-Electric Design of the Protection and Diagnostic Feeders of the HL-LHC Triplets
Authors: Pasdeloup F. , Prin H. , Williams L.
Published: June 2020

The HL-LHC Project currently undertaken by CERN that provides an upgrade to the existing LHC accelerator, is designed to increase the luminosity of the colliding particle bunches by a factor of at least five. Part of this upgrade will require the replacement of the existing groups of three superconducting LHC triplet magnets situated on each side of the ATLAS and CMS detectors with similar groups of four higher field HL-LHC triplet magnets of a new design that exploit coils manufactured with cables in Nb3Sn superconducting alloy. The HL-LHC triplet magnets require dedicated electric current feeders linking their cold masses to their cryostat vacuum vessels, thermo-electrically optimised and specifically designed to separately feed their quench protection, beam tuning and instrumentation systems with electric current. The HL-LHC instrumentation feedthrough system is similar, though containing a larger cable inventory, to that mounted on existing cryo-magnets in the LHC accelerator whereas the quench protection and beam tuning systems, both present new requirements calling for a substantially different design approach. Installed in a highly activated zone of the LHC, all three systems consequently exploit only natural heat convection to prevent the formation of condensation at their warm ends. This paper describes the functional design and thermo-electrical optimisation achieved for each of these electric current feeder systems.
Thermal engineering of optical mirrors for use at cryogenic temperature inside a LHC magnet cryostat
Authors: Micolon F , Dijoud T , Durand H Mainaud , Parma V , Rude V , Sosin M
Published: June 2020

In the frame of the HL-LHC project, innovative technical solutions are sought to measure accurately the position of the magnet helium vessel inside the cryostat. To this end, a system based on laser-interferometry is being designed to monitor the displacement of the vessel through dedicated openings in the new HL-LHC magnet cryostats. In order to test such a system on a full-scale setup in representative operating conditions, a LHC dipole cryostat was modified to integrate the system optical lines of sight and the reflective mirrors were mounted onto the magnet helium vessel.

Upon the first cool down of the magnet to 80 K, severe ice-like condensation started forming on the reflective surface of the mirrors hence making the system unusable at cold. This was attributed to the condensation of the residual gas remaining in the cryostat insulation vacuum on the mirror surface. In this configuration the mirrors acted as local “cold spots” since they were purposefully sticking out of the multi-layer insulation (MLI) that is otherwise covering the magnet helium vessel.

In order to cope with this condensation issue, a dedicated study was carried out to design and manufacture a passive temperature regulation system based on a thermal insulating support and a thermal radiation intercept in order to keep the mirrors just above the expected freezing temperature in operational conditions.

This paper details the thermal engineering study leading to the design of the insulated mirrors and presents the technical solution retained as well as the latest test results.
Demonstration of CW accelerating gradients on a cryogen-free, cryocooler conduction-cooled SRF cavity
Authors: Dhuley R C , Geelhoed M I , Zhao Y , Terechkine I , Alvarez M , Prokofiev O , Thangaraj J C T
Published: June 2020

Conduction-cooling of superconducting radiofrequency (SRF) cavities using closed-cycle cryocoolers can lead to compact linear accelerators by eliminating liquid helium and the associated infrastructure. In this paper, we present the first-ever experimental demonstration of continuous wave (CW) accelerating gradients on a niobium SRF cavity that is cooled without using liquid helium. In a newly developed experimental apparatus, a single-cell, 650 MHz niobium cavity was conductively coupled to a 2 W @ 4.2 K pulse tube cryocooler using a high-purity aluminum thermal link. The CW accelerating gradient slightly exceeded 1.5 MV/m, a limit imposed by our RF power supply. Using simple scaling, we project that the niobium cavity when coated with Nb3Sn and operated on the same experimental setup can produce >10 MV/m CW accelerating gradients.