bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fluid mechanical response of a pulse tube cryocooler: modelling and experimental validation
Authors: Lauzier K , Bribiesca-Argomedo F , Gauthier J-Y , Sesmat S , Lin-Shi X , Carvalho Lopes D 
Published: June 2020

Abstract
Earth observation satellites require cryocoolers to cool down their infrared imagers at very low temperatures. Besides having very good thermodynamic performances, satellite cryocoolers are expected to generate as little vibrations as possible. In order to better understand vibration causes between 50 and 500 Hz, a precise model of the whole cryocooler is necessary. In the literature, two main modelling approaches for pulse tube cryocoolers exist: compressororiented models reduce the thermodynamic system to a linear mass-spring-damper system acting on compressor’s pistons; and thermodynamically oriented models aimed at understanding and predicting thermodynamic performances.
In this paper, the mechanical behavior of the thermodynamic system is modelled. Assumptions concerning gas properties and thermodynamic behavior are made based on SAGE software simulations. A simplified Redlich Kwong equation is used. When necessary, polytropic coefficients were identified using simulation data, as were the time-averaged temperatures. The thermodynamic system is split into volumes, pipes and regenerators: conservation laws in volumes are integrated, dynamic mass and momentum conservation equations in pipes are solved using the method of characteristics and equations in regenerators are solved using a finite difference method. Three friction laws are used: one for straight pipes (Moody chart), another for wound pipes (White’s correlation) and a last one for porous media (Modified Ergun equation). Porosity is measured by weighing. The model is built to respect integral causality and propagation phenomena.
The developed model is validated using experimental data. The simulations highlight the non-linear mechanical behavior of the thermodynamic system: a sinusoidal motion of the pistons induces a non-sinusoidal pressure in the compression chamber. Among other, first and second harmonics amplitudes are about 3% of fundamental pressure amplitude.
This model can now be integrated into a global cryocooler model to predict compressor’s vibrations, power consumption or electrical harmonics. It could also be extended to predict vibrations from the thermodynamic system.
Sensitivity analysis on miniaturize pulse tube boundary layer losses
Authors: Ghavami Ali , Kirkconnell Carl , Mostafa Ghiaasiaan S 
Published: June 2020

Abstract
Miniaturized cryocooler systems are among the key components of state-of-art infrared sensing small satellites (SmallSats). To achieve small size, these cryocoolers need to operate at high frequencies, e.g., 200 to 300 Hz range. High frequency leads to lower compression and expansion swept volumes and hence a smaller cryocooler. Previously we showed that pulse tube cryocoolers have high boundary layer losses for small size pulse tube diameters, which results in low thermodynamic efficiency. In this follow-up study we present a sensitivity analysis on the pulse tube boundary layer losses and investigate the effects of the bounding temperatures, pulse tube aspect ratio, operating frequency and pulse tube diameter. Computational fluid dynamics (CFD) is used for this sensitivity analysis. The results allow us to find the threshold conditions beyond which a miniature pulse tube cryocooler can no longer be effective for use at high frequencies.
80 K vibration-free cooler for potential future Earth observation missions
Authors: Barreto J. , Martins D. , Branco M.B.C. , Ribeiro R.P.P.L. , Esteves I.A.A.C. , Mota J.P.B. , Branco J.B. , Gonçalves A.P. , Tirolien T. , Bonfait G. 
Published: June 2020

Abstract
A solution for a “vibration-free” Joule-Thomson cooler using a sorption compressor is presented to answer the needs of potential future Earth observation IR missions with low micro-vibration levels requirements from the European Space Agency. The adopted solution includes a closed cycle JT cooler, using nitrogen as working fluid with an expected cooling power of 1.5W@80K and the fluid circulation is achieved by cycles of adsorption/desorption using metal organic framework sorbent materials.
The working principle and chosen parameters of the 80 K vibration-free cooler are shown based on the various stringent requirements (temperature range, performance, consumption etc.) The characterization and validation of some components was already carried out: preliminary results are presented.
Experimental validation and refinement of mixture optimization for a mixed gas Joule-Thomson cycle
Authors: Detlor J , Gruenstern R , Pfotenhauer J , Nellis G 
Published: June 2020

Abstract
An initial prototype of a mixed gas Joule-Thomson (JT) cryocooler was constructed and installed in a test facility to experimentally validate and refine a computational tool developed to optimize the gas mixture composition for a Joule-Thomson cycle with specific operating parameters. The mixture optimization model determines an optimal three-component mixture based on the analysis of the maximum value of the minimum isothermal enthalpy change, ΔhT
, that occurs over the operating temperature range coupled with an evaluation of the percent of the heat exchanger that exists in a two-phase state within that range. The heat exchanger performance model has been refined and expanded to determine both the steady-state and transient operation of the system. The initial prototype of the JT cryocooler was installed in a test facility capable of providing and measuring a range of gas composition, molar flow rates, and pressures. The JT cryocooler has been operated while charged with several gas mixtures over a range of operating pressures. The pressure drop and temperature at the outlet of the JT valve were compared to the expected values based on the mixture optimization model. Results were used to refine the model, particularly the heat exchanger performance model, and gain confidence in its ability to steer future experimental iterations. A second prototype of decreased size with increased heat exchanger conductance, minimized parasitic heat loss and improved instrumentation is being developed to further investigate optimal mixture selection, particularly in the 120-150K cold head temperature range.
Thermodynamic comparison of small liquid nitrogen generators driven by mixed-refrigerant J-T refrigerators and gas expansion cycles
Authors: Wang H C , Guo H , Chen G F , Song Q L , Gong M Q 
Published: June 2020

Abstract
The thermodynamic comparison of small mixed-refrigerant J-T (MRJT) and gas expansion (Kapitza cycle) LN2 generators are conducted by the exergy method in this paper. Both of two types are employed for low pressure N2 liquefaction and air separation (< 9.0 bar). Pure N2, PSA units or cryogenic air separation columns are used for LN2 production. The MRJT type is driven by single-stage compressors. It is indicated that the efficiency of MRJT type is higher than Kapitza type. With pure N2 at 8.0 bar, the figures of merit (FOM) of MRJT and Kapitza types are 26.86% and 12.79%, respectively. With mini air separation columns, the FOM of MRJT and Kapitza types are 21.42% and 11.34%, respectively. The large exergy losses in the compressor unit and non-isentropic expansion are the main reasons of the inferior efficiency of the Kapitza type. In addition, the Kapitza type requires larger total compressor displacement than the MRJT type. The MRJT type is recommended to be used in small LN2 generators.
Design of the DUNE APATF cryogenic system
Authors: Dalesandro A , Voirin E , Montanari D , Tope T 
Published: June 2020

Abstract
Fermi National Accelerator Laboratory (FNAL) is developing the international Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) to advance neutrino science. The flagship of the DUNE project consists of a large particle detector constructed one-mile (1.6 km) beneath the surface at the Sanford Underground Research Facility (SURF) in Lead, SD. The SURF detector is the largest of its type ever built and is comprised of four cryostats totaling 70,000 tons of liquid argon (LAr) to record neutrino interactions with unprecedented precision. Each cryostat houses a detector, the first includes 150 Anode Panel Assemblies (APA) submersed within 17,500 tons of LAr. Before installing 150 APA within the SURF detector they will be cryogenically cooled to nominally 90 K at the APA Test Facility (APATF) utilizing nitrogen flows. The APATF cryogenic system is entirely located one-mile underground at the SURF facility and includes nominally 13 kW of refrigeration at 80 K, cryogenic transfer lines, APA test cryostats, a cryogenic control system, and various control and pressure safety elements to ensure performance and safety requirements are achieved. The APATF preliminary design is in progress and major considerations include an efficient, cost-effective mechanism to deliver the required refrigeration to the APATF underground, support of rigid testing intervals to support the DUNE operating schedule, temperature stability of the APA and electronics within cryostats, efficient cryogenic system operation to minimize heat leak and/or liquid nitrogen consumption, thermo-mechanical stability and flexibility of components, and pressure safety of the APATF cryogenic system. Installation and integration of the APATF cryogenic system within the footprint and to adjacent sub-systems is also discussed.
Progress towards Operation of a Deuterium Cold Neutron Source at the NCNR
Authors: Jurns J , Middleton M , Williams R 
Published: June 2020

Abstract
The NIST Center for Neutron Research (NCNR) operates a 20 MW research reactor that produces neutrons for a suite of 30 neutron scattering instruments. 70% of these instruments use cold neutrons (E<5 meV), which are moderated by two separate cold neutron sources. The cold moderator for both sources is liquid hydrogen (LH2), which is in turn cooled by a recently commissioned 7 kW, 14K helium refrigerator. NCNR plans to replace the larger cold source with a new one operating with liquid deuterium (LD2). This report focuses on progress towards the upgrade to liquid deuterium, and options to address the particular challenges of designing and operating a cooling system that simultaneously supports operation with both LH2 and LD2.
Cryogenic Performance Test Platform for the Gas Bearings of Helium Turbine Expanders
Authors: Li S S , Fu B , Zhang Q Y , Zhu P , Lu X F , Ma D K , Yuan K 
Published: June 2020

Abstract
The turbo-expander is the core part of the helium refrigerator, and the gas bearing is the critical component influences the stability of the machine. There is 300 K operating temperature difference between the turbine wheel and the gas bearing regions in the helium turbo-expander. Therefore, it is necessary to consider the heat transfer between the bearing surfaces, nominally at room temperature, and the rest of the machine when studying bearing dynamic stability. This paper describes a cryogenic test platform that is being developed to analyze the dynamic performance of gas bearings with cryogenic gas supply. The system flow loop has been designed for bearing and small turbine testing at 80 K and above. The experimental method has been determined. All of the components are ready for the cold box assembly. The commissioning of the platform will be carried out in the near future.
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.