bluuebunny/crossref_metadata_2025 huggingface dataset:
Further experimental work in mixed gas Joule-Thomson cryocooling
Authors: Detlor J , Pfotenhauer J , Nellis G
Published: July 2024

Miniature Joule-Thomson (JT) cryocoolers are attractive for many applications due to their small size and resulting fast cool-down time. Finned-tube heat exchangers are one of the most widely used heat exchanger for miniature JT cryocoolers. The basic configuration, known as a Giauque-Hampson (GH) or coiled tube heat exchanger, involves the high-pressure stream flowing through a finned-tube that is helically coiled upon a cylindrical core while the low-pressure return stream flows over the fins in the annular space created by the core and the inner diameter of a shell. The experimental work in this study aimed to gain insight into thermal characteristics of the shell-side of a GH heat exchanger by developing a test facility capable of measuring the two-phase heat transfer coefficient (htc) for this flow at operating conditions of interest to mixed-gas JT (MGJT) cryocooling. The capabilities of the test facility were demonstrated and measurements of the two-phase htc of the mixed gas on the shell-side of the GH heat exchanger prototype revealed that the shell side is the dominant thermal resistance for these operating conditions, even though the fins provide a larger surface area.
Characterization testing of the Air Liquide large pulse tube cryocooler (LPTC)
Authors: McKinley I M , Hummel C D , Johnson D L , Rodriguez J I
Published: July 2024

An Air Liquide large pulse tube cryocooler (LPTC) was parametrically performance tested for cold tip temperatures between 30 K and 200 K and heat rejection temperatures between 0°C and 40°C. The testing utilized a single off-the-shelf power supply to drive the compressor motors in parallel. The effect of compressor temperature and pulse tube inclination angle are also presented. In addition, the exported forces were measured at ambient conditions and the results are shown and discussed.
Characterization testing of the Thales LPT9310-HP cryocooler
Authors: McKinley I M , Hummel C D , Mueller B W , Johnson D L , Rodriguez J I
Published: July 2024

Two Thales LPT9310-HP commercial off-the-shelf (COTS) cryocoolers were parametrically performance tested for cold tip temperatures between 50 K and 250 K and heat rejection temperatures between 0°C and 40°C. Both coolers had identical transfer line configurations. The test results revealed small unit-to-unit thermodynamic performance variation. They are compared to test results of a COTS LPT9310 cooler with the same transfer line configuration. The effect of compressor temperature and pulse tube inclination angle are also discussed. In addition, the off-state heat leak as a function of inclination angle is presented. Finally, the feasibility of using a single LPT9310-HP COTS cooler in a two-stage configuration is discussed.
Vibration-Free 40-80K Turbo-Brayton Cryocooler and its Very High Efficiency Recuperator for Earth Observation Instruments
Authors: Dalban-Canassy M , Rehayem E , Ungureanu A , Salquebre Q , Berindei J
Published: July 2024

Several studies have demonstrated that Reverse Turbo-Brayton cryocoolers could be the next space cryogenic revolution, thanks to their capability to provide vibration-free remote cooling in the temperature range of 4 to 150K and for medium to high cooling powers. With this motivation, Absolut System developed a very low vibration 40-80K Reversed Turbo-Brayton cooler, work performed under the ESA Technical Program Technical Research Program - 4000113495/15/NL/KML. The cooler is based on two turbo-compressor stages, a high efficiency recuperator and a cryogenic turbo-expander, for operation between 300 and 40K. Following the fabrication of the cooler, we performed tests on both individual components, compressors, expander and recuperator as well as on the complete cooler. The turbomachines use aerodynamic bearings, i.e. contactless bearings, generate very little vibrations and exhibit no wear over time. The characterizations performed during the project concern exported micro-vibration behaviors of the compressors and the expander, operating respectively up to 250,000RPM and 150,000RPM, and thermodynamic performance of the different elements. The cooler was tested down to its minimum temperature and required the development of specific operating procedures for the conditioning of the circuit. We report here in a first part the main results and observations stemming from the test campaigns carried out during the project. This work showed the necessity of putting additional effort into the recuperator, one of the most critical components of the cooler. Absolut System is thus also working in parallel on developing a very high efficiency and compact heat exchanger, which we report in a second part, for the specific needs of Turbo-Brayton Coolers in response to the ESA Proposal ESA-TDE-TECMTT-SOW-023649. The technology selected for this is based on the common tube and shell but using very thin tubes of small diameters (<1mm). The challenge of this exchanger is not only the manufacturing, but also the very stringent requirements. Obtaining an efficiency higher than 97.5% in a very small mass while maintaining very low pressure drops, makes for a very challenging project. We have performed the design phase, tested, and validated different aspects of the assembly. The design for the first breadboard model has been validated numerically and is in the fabrication process. Testing the exchanger will then take place to characterize the performances of the recuperator and allow for a comparison between experimental results and analytical and CFD models. This effort participates in placing the Turbo-Brayton cryocoolers at the forefront of space coolers and pushing Europe even further in State of Art advancements for space to bring us closer to fulfill future Space Explorations and Earth Observation missions.
Efficiency Improvement of Small Cryogenic Helium Turbo-expanders in TIPC
Authors: Ke Changlei , Xiong Lianyou , Peng Nan , Dong Bin , Li Kongrong , Zhang Xiaohua , Liu Liqiang
Published: July 2024

An experimental helium liquefier/refrigerator, using ultra high speed cryogenic turbo-expanders is designed and developed in Technical Institute of Physics and Chemistry (TIPC), and liquefaction rate of around 42 L/hr and refrigeration capacity of around 130 W @ 4.5 K is achieved. The turbo-expander constitutes the most critical component of a helium liquefier/refrigerator causing that the turbine efficiency has a great influence on the performance of the whole cryogenic process plant. Inlet Flow Radial (IFR) turbine design is dictated by criteria like velocity ratios. For small flow rate plants the size of the turbine impeller needs to be reduced. In order to reach a high efficiency, the rotational speed must be increased to complete a large specific enthalpy drop. The present article describes the latest technical developments at TIPC, including results obtained during field trials with the TIPC helium liquefier and refrigerator. The motivation of these developments is to improve the efficiency of the machines, and also to widen the range of operation.
Research on the State Equation of High-Pressure Expansion Process of Liquid Hydrogen
Authors: Wu Q , He M , Yang S Q , Xie X J , Gong L H
Published: July 2024

Liquid hydrogen, characterized by high purity, efficient storage and transportation, and renewable clean energy, has become a crucial component in the efficient utilization of energy. A profound understanding of the thermodynamic properties of the high-pressure expansion process of liquid hydrogen plays a significant role in the utilization of hydrogen energy, the development of liquid hydrogen booster pumps, and the implementation of liquid hydrogen-related projects. In this paper, starting from the perspective of the state equation, we conduct research on the large-scale high-pressure expansion process of liquid hydrogen. Several commonly used state equations are employed to calculate the PVT (Pressure-Volume-Temperature) values of this process, and appropriate modifications and combinations are made to improve the accuracy of the state equations. The advantages and disadvantages of the different equations of state for each pressure range and the causes of errors are further discussed based on the standard values given in the NIST database, and some suggestions are made for the improvement of the equations of state and the design of liquid hydrogen-related equipment.
The study of active gas-gap heat switch using carbon nanotubes as the adsorption material
Authors: Yu F Q , Pan T , Li K , Zhu Z Z , Wei F , Dai W
Published: July 2024

Heat switches are widely used in cryogenic systems and play an important role in controlling thermodynamic cycles and accelerating the cooling of cryogenic components, etc. Among them, the active gas-gap heat switch, as one of the mainstream heat switches, mostly uses activated carbon as the adsorbent. It desorbs/adsorbs helium by heating/cooling the activated carbon to realize the ON/OFF state. Normally, a short response time, which is related to the adsorption properties of the materials and the heating method of the adsorption bed, is desired. In order to further shorten the response time and improve the performance of the heat switch, a 3He active gas-gap heat switch using carbon nanotubes as the adsorption material was investigated. About 0.06 mW/K OFF-state conductance and 60 mW/K ON-state conductance were obtained at 4 K. The heat switch switched on within 35 s when 1.6 mW heating power was applied to the adsorption bed, and it took about 400 s at 4 K to reduce thermal conductance to 1/10 of ON-state conductance when the heating of the adsorption bed was stopped.
Nitrogen precooling heat exchanger replacement and control system upgrade in superfluid cryoplant at CMTF
Authors: Subedi J , Hansen B , White M , Patel V , Makara J , Atassi O , Johnson G
Published: July 2024

Liquid nitrogen precooling is used in most cryoplants to achieve cooldown to 80 K temperature range. In one such system at Fermilab’s CMTF superfluid cryoplant, where the helium supply directly exchanges heat with liquid nitrogen, freezing of nitrogen occurred inside the heat exchanger due to heat exchanger flow imbalance during a cryoplant trip. Trapped vapor pockets of nitrogen within the frozen heat exchanger channels were formed while warming up the heat exchanger, creating high localized pressure and subsequent damage/rupture of the heat exchanger. Replacement of the heat exchanger was done, and modifications were made in the system to rectify future occurrences. The control system was updated to bypass the heat exchanger entirely if the incoming helium stream temperature drops below 76 K. This was done by repurposing two control valves as heat exchanger bypass valves that were previously used for a redundant 80 K adsorber in the coldbox. Additional modifications were made to further prevent return of large amount of cold helium gas from cold end during abrupt cryoplant shutdown. This modification has ensured high reliability of heat exchanger with prevention of freezing of nitrogen which can damage the heat exchanger.
Thermal performance and stability experiments of a 1.75-meter-long helium pulsating heat pipe
Authors: Kossel L , Pfotenhauer J , Miller F
Published: July 2024

Experimental studies of the performance and thermal stability of extended-length helium pulsating heat pipes (PHPs) were performed at the University of Wisconsin – Madison. Multiple distinct testing procedures were carried out on helium PHPs with an adiabatic length of 1.75 meters, such as progressively increasing evaporator heat load, randomized heat load, and extended period tests. The results of these tests show that despite the stochastic nature of the fluid flow and persisting non-equilibrium conditions, long-distance helium PHPs can maintain stable and steady operation with excellent thermal performance. The progressively increasing heat load tests serve as a baseline for the 1.75-meter PHP’s performance, where the maximum effective conductivity observed was 443.4 kW/m-K at 570 mW heat load and a fill ratio of 56.42%. Furthermore, the randomized heat load test show that, with an optimized fill ratio, PHP performance is not strongly dependent on previous operating conditions and that normal operation can be swiftly recovered from a dry-out condition. The extended period test shows a stable, pseudo-steady operation for over 50 hours with no performance degradation or temperature deviations observed. The impact of PHP build quality is also discussed.
Neon pulsating heat pipe with innovative flexible evaporator to facilitate cryocooling of superconducting devices
Authors: Dixit T , Authelet G , Mailleret C , Gouit F , Stepanov V , Baudouy B
Published: July 2024

Cryogenic pulsating heat pipes (PHP), also termed oscillating heat pipes, are passive thermal links that transfer heat by oscillatory motion of two-phase cryogen confined in serpentine-shaped capillary tubes. It is composed of three sections, namely, the condenser (cold sink), the evaporator (heat source) and the adiabatic part that can range from several centimetres to few metres. In spite of longer lengths, PHPs hold an advantage that their weight does not radically increase in comparison to counterparts like metallic thermal straps. The aim is to present cryogenic PHPs as one of the potential thermal links aiding in distant cooling of superconducting devices from active cryocoolers. A 0.4 m long neon PHP with 1 mm capillary tube diameter has been recently developed characterized by one of the highest thermal conductance reported till date both in vertical and horizontal orientation. An innovative modification in the construction of PHP evaporator is showcased in this article. This would considerably enhance the flexibility of PHPs in terms of their employment geometrically within the targeted application. Pilot experimental results for neon PHP coupled with the altered evaporator is presented for heat load up to 18 W.
Initiation and suppression of Taconis oscillations in tubes with junctions and variable-diameter tube segments
Authors: Shenton M P , Matveev K I , Leachman J W
Published: July 2024

Taconis oscillations represent spontaneous, usually unwanted excitations of acoustic modes in narrow pipes going from warm ambient environment into cold cryogenic space. These oscillations can drastically magnify heat leak and create vibrations undesirable for measurement instruments. In this study, modifications of a classical constant-diameter-tube Taconis setup are investigated. Specifically, variable-diameter tubes were found to strongly affect excitation, with wider tube segments in the warm environment encouraging oscillations, while additions of properly chosen pipe network configurations can supress the oscillations. The low-amplitude thermoacoustic theory, previously developed for thermoacoustic engines and refrigerators, was adapted for modelling Taconis phenomena, accounting for finite-length segments with temperature evolution where thermal-to-acoustic energy conversion takes place. Experiments were conducted using primarily hydrogen as a working fluid to validate theoretical predictions. With the rapid development of various hydrogen storage and transfer systems, it is expected that Taconis oscillations may become an issue, and this study provides an initial modelling framework to assess this phenomenon in hydrogen systems.
Cryopump concept development for the cryogenic mirror region of the Einstein Telescope – the future gravitational wave observatory
Authors: Hanke Stefan , Luo Xueli , Battes Katharina , Day Christian
Published: July 2024

The Einstein Telescope (ET), the planned gravitational-wave observatory for Europe, will increase the sensitivity and expand the observation band to lower frequencies. The main optics of the ET-Low Frequency (LF) interferometer will be cooled to cryogenic temperatures below 20 K and the whole system, consisting of the beam pipes, the suspension towers and the cryostat containing the mirror, requires high to ultra-high vacuum conditions.

To fulfill the vacuum related requirements the use of tailor-made in-situ cryopumps is envisaged. Simulations at KIT, performed with the in-house Test Particle Monte Carlo code ProVac3D and a simplified model of the system, considered the three main gas sources from the neighbouring systems and the sinks by pumping stations distributed along the pipe arms, the cryogenic pump sections close to the mirror and the cryogenic mirror environment. These simulations showed different needs for the pumping of hydrogen (to lower the residual pressures) or heavier species like water (to lower the frost formation on the cryogenic mirror surface) – depending on the position related to the mirror. With these findings, the development of a pump arrangement concept was worked out.

In parallel, the outgassing rates of the inner walls of the beam pipe tubes, influencing strongly the vacuum pumping demands, have been varied to investigate the potential use of mild steel as a beam pipe material of reduced costs.

This paper describes the developed pump arrangement concept, utilizing cryogenic pumps integrated into the beam pipe tubes of 1 m diameter, with their individual objectives regarding pumped species and needed temperatures.

Furthermore, the key parameter of frost formation on the cryogenic mirror, important for long operational phases without pause and maintenance, being also a design driving demand, is derived from the predicted residual pressure of sticky gases like water.
Thermal analysis of a FEL SCU cryostat
Authors: Shiroyanagi Y , Anliker E , Hasse Q , Ivanyushenkov Y , Kasa M , Fuerst J
Published: July 2024

An ANL-SLAC collaboration is working on the design of a planar superconducting undulator (SCU) demonstrator to be tested at the SLAC Free Electron Laser (FEL). The demonstrator cryostat is multi-segmented, and each segment includes an ∼1.5-m-long superconducting undulator as well as other magnetic components like a phase shifter and a beam position monitor (BPM). This LHe-based cryostat is cooled by two stage pulse tube cryocoolers (Cryomech PT425-RM). A detailed load map of the cryocooler was measured and benchmarked with the manufacturer’s load map. A thermal model of one segment of the cryostat, which includes all cooling circuits, has been created in ANSYS and analyzed using the measured cryocooler load map. This paper presents the calculated cooling power requirement and the temperatures in the cryostat.
Additive Manufacturing of cryogenic materials
Authors: Rehme O , Weidermann C
Published: July 2024

The use of pure copper and Inconel 718 as cryogenic materials has been well known in the cryogenic materials space. Despite their potential, little is known about the use of these materials in cryogenic environments regarding their ability to withstand these conditions when manufactured using Additive Manufacturing (AM) methods. AM has emerged as a promising production method due to its ability to produce complex geometries and near net-shape parts. Copper and Inconel 718 offer a wide range of uses in cryogenic applications, as Copper being highly conductive makes it ideal for electrical applications, whilst Inconel 718 serves well as an engineering material.

In this paper, we demonstrate the Coldgas Spraying (CS) of copper and the Selective Laser Melting (SLM) of Inconel 718 and Scalmalloy as the AM processes of choice for each respective material. The main distinction between both processes is that CS is useful for rapid deposition of material in the range of several kg/h whereas SLM is limited to a range of several hundred g/h. However, CS can only yield bulk structures while SLM allows the production of fine and intricate structures due to the nature of their approaches.

The work presented here was performed in the framework of a research project named AdHyBau. It is funded by the German government in which several partners from industry and academia seek to jointly develop a 500 kW output power electric drive for aviation applications which employs liquid hydrogen as a propellant for a fuel cell but also for advanced cooling to obtain very high power densities in the range of above 10 kW/kg.
Cryogenic aspects of a 20 MW class low-temperature superconducting generator for the renewables industry
Authors: Stautner W , Torrey D , Xu M , Wu A , Parizh M , Soni V
Published: July 2024

In this paper we give a progress update on the cryogenic design for cooling a 20 MW class, partially superconducting generator with stationary field coils for offshore wind renewables industry [1-2]. This is a continuation of an earlier program on a 10 MW system dating back ten years. Whereas this new power rating increase leads to a radial diameter expansion of the superconducting field coils from 4 to > 9.5 m, it maintains the axial length. We show the design based on this scaled up with enlarged diameter. The field coil size increase asks for higher cooling power that leads to a bigger cold box size to accommodate the cryocoolers. In the design, as many as 8 cryocoolers can be accessed and serviced from the nacelle that houses the main cryogenic components. A typical thermal load balance sheet with all components is given and compared against the available cryocooler cooling power at different operating conditions. Due to the cryocoolers’ local point of contact cooling within the nacelle, the temperature gradient of the thermal shield that fully encloses the cold mass with its embedded field coils needs to be balanced out to minimize the heat burden on the field coils. This requires additional analytical efforts and implementation of further design features. The extended nacelle houses the cold box with its cryogenic infrastructure. The interface for the envisaged cryogenic pushbutton closed-loop circulating system remains invisible, requires no handling of cryogenic liquids and is hermetically closed. The field coil diameter increase also leads to a greater initial helium gas storage volume. In addition, it requires higher initial room temperature fill pressure within the toroidal helium vapor storage tanks and in cooling tubes connecting to the cryocoolers. The toroidal helium gas tanks are thermally coupled with the thermal shield so that helium convection inside the storage tank can improve heat transfer and reduce the temperature gradient of the thermal shield. Besides those heat transfer challenges, additional mechanical strain within this large structure is exerted on the torque tubes during initial cooldown and when energizing field coils. Some of those design challenges are quite unexpected, leading to novel workarounds in order to maintain the chosen cooling strategy. Finally, we assess those design limitations in view of further cryogenic scalability with emphasis on manufacturability and assembly.
Tuning hydrogen boil-off via inert gas insulation purge in a vapor cooled shielded fuel tank
Authors: Gitter Y K , Leachman J W
Published: July 2024

Vapor cooled polymer composite tanks for liquid hydrogen are a newopportunity for light weight power-system integration into unmanned aerial vehicles. Vapor shielding has the ancillary benefit of pre-conditioning the hydrogen for use by a fuel cell. However, the mass flow rate required by a fuel cell should be matched by the natural boil-off rate of the tank. With limited ability to vary insulation thicknesses, the challenge becomes satisfying the fuel cell consumption in UAVs at different mass flow rates when at varying stages of flight from take-off, cruise, and landing. This paper provides experimental measurements of mass flow rate of hydrogen from the tank considering batch purging with helium or argon in the vapor cool shielded insulation layer. A 5-shell vapor cooled shielded tank is used with two layers of insulation including aerogel, helium or argon, and two vapor channels. A more complete understanding of system-level thermal conductance is determined by mass flow of hydrogen leaving the tank during hypothetical flight.
Uncertainty analysis of Raman spectra for measuring ortho-parahydrogen compositions
Authors: Appel K R , Leachman J W
Published: July 2024

Determining ortho-parahydrogen compositions at cryogenic temperatures is an important quality control for liquid hydrogen custody exchange. High orthohydrogen compositions lead to an exothermic reaction resulting in increased boil off and increased venting losses of liquid hydrogen product by either the supplier or consumer. Traditional methods for measuring ortho-parahydrogen compositions such as hot-wire anemometry, nuclear magnetic resonance, and infrared spectroscopy are typically inconvenient at best. As the number of cryogenic hydrogen systems continue to increase, there is an increased need for flexible, standardized techniques for post processing composition measurements. A Raman spectrometer implemented in the Cryo-Catalysis Hydrogen Experimental Facility (CHEF) has demonstrated incredible flexibility for composition measurements of cryogenic hydrogen flows through a wide range of temperatures and pressures with the Raman probe in-situ at cryogenic temperatures. This article analyzes the uncertainty of Raman spectroscopy data of cryogenic hydrogen equilibrated at temperatures in IONEX catalyst. Spectra from hydrogen catalyzed to the equilibrium ortho-parahydrogen composition are processed and compared to expected statistical distributions for method verification.
Model establishment and process analysis of liquid hydrogen energy storage
Authors: Zhang Zhaoxue , He Ming , Zhou Han , Gong Linghui
Published: July 2024

Under the general trend of energy reform, the key role of hydrogen energy has been becoming increasingly prominent. Hydrogen is not only an ideal efficient clean energy, but also commonly used as a cryogenic working medium, in the field of cryogenics and refrigeration. Compared with gas phase at high pressure, liquid hydrogen (LH2) has advantages such as high density and low transportation cost, which make it more suitable for large-scale development. As an energy storage medium, LH2 provides cold energy and electricity to smooth out fluctuations and reduce abandonment of wind and solar. However, there are few studies on the comprehensive LH2 industry chain of production-storage-transportation-utilization.

In this article, a model and analysis of the energy storage process utilizing LH2 is established. This includes purification and liquefaction, storage and transportation, regasification, power generation, and other related processes. The selection of appropriate methods and equipment is systematically addressed. Furthermore, an evaluation is conducted on its efficiency, economy, environmental impact and expansibility, in comparison with other energy storage methods. Ultimately, these findings aim to seek solutions for rationalizing efficient and low-cost utilization of LH2 energy storage, and provide novel insights into the practical application of hydrogen energy.
Ortho-parahydrogen catalyst test facility
Authors: Eisenhut S , Haberstroh C
Published: July 2024

With the growing interest in hydrogen as one pillar of the future energy economy, the relevance of hydrogen liquefaction for storage and transportation is increasing rapidly. However, the liquefaction process still offers much potential for improvement in terms of cost and efficiency. One problem faced with achieving more cost- and energy-efficient liquefiers is the uncertainty associated with the dimensioning of the ortho-para converters. Literature data on the existing ortho-para catalysts stem mainly from the 1950s and 1960s and are partly inconsistent. Therefore, a new facility for the comprehensive investigation of catalytic ortho-parahydrogen conversion was set up at the Dresden University of Technology (TU Dresden) as part of the government-funded HyCat (“Improvement of the Ortho-Para-Catalysts for Hydrogen Liquefaction”) project. It enables the testing of catalysts in the whole operational range of ortho-para converters in modern large-scale liquefaction plants by allowing the independent variation of temperature, pressure, flow rate, inlet ortho-para ratio, and sample reactor internal geometry. The setup has been tested and validated preliminarily. It can soon be used to produce new high-quality data sets on the performance of the commercial catalyst Ionex (hydrous ferric oxide), for the qualification of alternative catalysts, and for gaining a deeper understanding of the reaction kinetics involved.
Mobile hydrogen liquefaction and storage system
Authors: Glenn M , Kim H , Coleman B , Guerrero M , Goetchius B , Pratt R , Baik J , Fesmire J , Williams M
Published: July 2024

A mobile hydrogen liquefaction and storage unit has been developed to demonstrate the liquid hydrogen (LH2) value chain including hydrogen production, liquefaction, storage, transfer, and recovery. This unique LH2 technology demonstrator, or LS20 mobile system, is one of the primary systems for a multipurpose LH2 test platform that evaluates liquefaction, controlled storage, and zero-loss transfer (ZLT) methodologies. The LS20 system has been designed, fabricated, and tested at GenH2. The primary subsystems include an electrolyzer option, gas precooler, Ortho-Para hydrogen converter, cryocooler-based hydrogen liquefier, portable LH2 storage tank, ultralight LH2 vehicle tank for aviation application, safety devices and sensors, automated venting system, associated sensors, instrumentation, and control system. The system was successfully demonstrated by continuous hydrogen liquefaction according to the design specification with the help of an automated control system to maintain the liquid at a desired level without boiloff loss. In addition to liquefaction and controlled storage, the functions of zero-loss transfer, boiloff gas recovery, and re-liquefaction were also demonstrated. The results provide proof-of-concept data for future LH2 infrastructure design as well as the critical LH2 refilling and servicing methodology for many hydrogen mobility applications. The system design, fabrication, operational methodology, and test performance results are discussed.
Effects of throttle and heater input for reducing pressure surging in a liquid hydrogen tank pressurizer
Authors: Gitter Y K , Leachman J W
Published: July 2024

Ensuring uniform flow from a liquid hydrogen storage vessel to a consumer requires pressure maintenance within ullage space. Large changes in volume during vaporization of liquid hydrogen allow a percentage of flow to be diverted from the consumer for tank ullage pressure maintenance. The return state of the hydrogen should be close to saturated vapor at comparable volumetric flow rates for liquid extraction and smooth operation. This paper details the theory, design, and experimental performance of a hydrogen pressurization system for controlling this return state. A cartridge heater, throttle, and manual valve are utilized to vaporize, reduce pressure and pressure oscillations, and control flow. Experimental measurements are compared with theoretical predictions for liquid nitrogen and liquid hydrogen flows. The end results demonstrate the performance of the heater and throttle for pressure maintenance of ullage within a liquid hydrogen tank.
Model Based Exploration of Physical Parameters for Liquid Hydrogen System Insulation Performance
Authors: Maynard N , Louriou C , Estebe B
Published: July 2024

Cryogenic Systems require a highly efficient insulation so as to limit the heat ingress and boil-off, which is generally achieved through the use of vacuum combined with an insulated media. The performance of Multi layer Insulation (MLI) will be investigated with detailed thermal models developed to account for all the heat transfer contributions, solid conduction, gaseous conduction and radiation. Results are presented for an usual cold vacuum pressure (CVP) corresponding to high vacuum (<10−6 torr) and compared with available experimental measurements for state of the art technologies. The nominal thermal performances are then evaluated for a cold temperature of 20K (representative of liquid hydrogen storage temperature), for a degraded CVP with hydrogen and nitrogen as residual gasses and for increased hot boundary temperatures. Other parameters are also discussed such as, the number of layers, material, layers density, venting options, assembly process and material optical properties. Finally, a sensitivity of the thermal performance is also presented with a pressure gradient through the insulation thickness, that could be induced by cryopumping, materials outgassing, pumping times or small leakages.
Impact of Internal Baffle Designs on Liquid Hydrogen Sloshing in Cryogenic Aircraft Fuel Tanks
Authors: Ryali L , Stautner W , Mariappan D
Published: July 2024

Hydrogen because of its zero carbon emissions and highly energy-dense nature has a strong potential to be used as an aviation fuel. There are currently two main ways that hydrogen is being considered for use in aircraft: it can be vaporized and mixed with air before being burned in the jet engine, or it can be used to power fuel cells that generate electricity, which can be used to power electric motors. Both these scenarios would require storing liquid hydrogen (LH2) in cryogenic tanks on board as it minimizes the tank size. But a major challenge with cryogenic hydrogen storage is the dynamic movement of the fuel which can lead to fuel boil off and bubble formation. In the current paper, the sloshing motion of LH2 in a CHEETA type thin-walled composite fuel tank, under acceleration data obtained from an Airbus A-320 in cruising conditions, is investigated. The dynamic fluid structure interaction problem is solved numerically using the Coupled Eulerian-Lagrangian (CEL) technique in ABAQUS. The developed modelling strategy is then employed to study the impact of various internal baffle designs on the sloshing behavior of the fuel under different fill levels. This study not only establishes that sloshing is a major cause for concern when it comes to LH2 aircraft fuel storage, but also advances our understanding in devising potential mitigative strategies.
Development of a research cryostat for direct thermoacoustic cooling and conversion of hydrogen
Authors: Shenton M P , Leachman J W , Matveev K I
Published: July 2024

Hydrogen thermoacoustics is a relatively unexplored but promising topic for development of new cryocoolers and hydrogen liquefaction. This paper describes a new research cryostat designed to investigate hydrogen as a working fluid in thermoacoustic systems. The cryostat is a modular, turbo-molecular pump driven, vacuum chamber with a 4.2 K pulse-tube cryocooler capable of 45 W of cooling at 50 K. Using this cryostat, a feasibility study of direct thermoacoustic cooling with ortho-parahydrogen conversion is initiated. An acoustic resonator system is designed to have the fundamental acoustic mode excited via imposed temperature gradient in a porous stack between the ambient environment and cold bar connected to the cryocooler. The generated acoustic waves transfer heat inside another porous stack to produce a refrigeration effect at cryogenic temperatures. In addition, the regenerator solid matrix will be catalyzed for ortho-parahydrogen conversion to demonstrate a novel combination of cooling and conversion of cryogenic hydrogen in a single device. Design, construction, and performance of the cryostat and modelling results for one thermoacoustic system are reported.
Commissioning of the hydrogen cryostat of the cryogenic moderator system of the European Spallation Source (ESS) for test purposes at the ZEA-1
Authors: Rosenthal E , Bessler Y , Hannot M , Natour Prof G
Published: July 2024

A helium-cooled hydrogen cryostat for the European Spallation Source (ESS) was developed, built and tested at the ZEA-1 of the Forschungszentrum Jülich. In order to be able to carry out the final factory acceptance test (FAT), a nitrogen mixing system was developed with which the cryostat could be cooled down and operated in a controlled manner. During the test phase, the cryostat was operated exclusively with nitrogen instead of helium and hydrogen. Nevertheless, all functions of the cryostat system could be checked and key figures could be determined.
Spallation Neutron Source reliability improvement projects for the Cryogenic Moderator System
Authors: DeGraff B , Armstrong R , Denison J , Howell M , Pinion L , Stewart S
Published: July 2024

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) operates the Cryogenic Moderator System (CMS) which provides supercritical hydrogen cooling at 20K to three neutron moderators. A helium refrigerator provides 8 kW of cooling capacity to three parallel hydrogen circuits. Several projects have been completed to improve the operational reliability of the CMS. The status of helium compressor oil removal system, helium oil processor, helium purity monitoring, hydrogen circulator bearing investigation and operational procedure improvement will be presented. Future plans for sustained reliable operation at design capacity will also be presented.
Design, development and commissioning of the control system for the cryogenic distribution system at ESS
Authors: Asensi E , Arnold P , Van Velze P , Magnusson E , Nilsson P , Zhang J , Domagala D , Binczyk W , Gaj W , Maciocha W
Published: July 2024

The cryogenic distribution system (CDS) at the European Spallation Source (ESS) connects the refrigeration plant with the linear accelerator, consisting in 13 spoke and 30 elliptical cryomodules that are cooled at 2K via multi-transfer lines, individual valveboxes for every cryomodule and an endbox. The designed control system monitors and controls the cooling helium flow through the CDS. The controls architecture for the CDS is based on one Programmable Logic Controller (PLC) per valvebox and another one for the endbox, which are integrated into EPICS through the Controls Network and takes care of the process functions, making it a total of 44 PLCs. This type of integration allows for the remote operation of the CDS from the control room and the necessary interaction of the control system with other related systems and EPICS services like archiving, alarms and save-and-restore. Pre-commissioning activities like loop checks, temperature curve validation, pressure sensor calibration and valve initialization started in summer 2022. Eventually, the system was ready for commissioning and a first cooldown was performed in December 2022. The paper describes the design, development and commissioning of the control system and diverse challenges during the deployment and commissioning activities. Future activities are discussed including the implementation of a sequencer for automatic cooldown and warmup, integration with the cryomodule controls and a master PLC to handle the helium management.
A protocol for accurately calibrating thermocouples at cryogenic temperatures
Authors: Purandare A S , Vanapalli S
Published: July 2024

To study the quenching characteristics of materials in a cryogenic liquid bath transient temperature measurements of high accuracy are necessary. Thermocouple is an ideal tool for this application because of its low self-heat capacity. However, they require calibration before usage that require multiple fixed-point temperatures. The common fixed-point temperatures are the water-ice melting temperature, the dry ice sublimation temperature, and the boiling temperature of liquid nitrogen. It is important to note that there are uncertainties associated with dry ice sublimation and liquid nitrogen boiling temperature inherent to the heat and mass transport phenomenon at their phase-changing interface or inside the bulk medium. The dry ice temperature is influenced by the mass transport phenomenon occurring at the interface between the dry ice and the ambient surrounding it. In a typical lab environment, dry ice temperature is significantly lower than the commonly quoted sublimation temperature of -78.5 °C at 1.013 bar. In the case of liquid nitrogen stored in a cryostat, temperature gradients develop in the liquid bath. This paper describes a protocol for calibrating thermocouples by accurately defining and using fixed-point temperatures of dry ice in a saturated environment and a liquid nitrogen slush.
Development of test rig for optical diagnostics of cryogenic spray
Authors: Patil Bhushan R , Twarog Kyle , Mannaa Ossama , Sung Chih-Jen
Published: July 2024

Spray cooling is the primary method for conducting chilldown and fill of cryogenic propellant tanks. In a typical spray injection process, a liquid sheet/jet that exits the spray nozzle undergoes primary breakup by the development of surface instabilities. Droplets and ligaments generated after the primary breakup undergo secondary breakup to create a dispersion of droplets, which extract heat on impact with the tank walls. In the existing literature, there is limited data on the primary breakup of cryogenic sprays and their detailed visualization. Moreover, an insight into the spray characteristics such as primary breakup length and cone angle is vital to the development of computational models. In this investigation, optical diagnostics of cryogenic spray breakup and measurements of cryogenic spray characteristics have been conducted. Liquid nitrogen is the selected cryogen for the present analysis. To capture the transient nature of spray breakup after the injection, a novel shadowgraph technique is developed to photographically freeze the spray motion. Cryogenic spray characteristics such as cone angle and primary breakup length are obtained from the shadowgraph. In addition, droplet velocity measurement using Particle Image Velocimetry is explored. The comprehensive experimental dataset obtained herein not only provides insights into the mechanism of spray formation for cryogenic fluids but also helps in designing of spray cooling system for tank chilldown.
Capacitance-based measurement of volume fraction, velocity, and mass flow rate of cryogenic nitrogen two-phase flow
Authors: Straiton Benjamin J , Charleston Matthew A , Marashdeh Qussai M
Published: July 2024

Cryogenic fluid flow is a critical measurement parameter but is difficult to properly measure due to the extreme environmental conditions and the frequent presence of multiphase flow during saturated liquid transfers. Multiphase flow proves challenging for most flow measurement methodologies; furthermore, additional measurements of volume fraction, quality, and slip velocity are often required. In-line capacitance-based sensors have the potential to overcome these limitations. In this paper, a capacitance sensor in a multiphase cryogenic flow loop is evaluated for its ability to measure liquid volume fraction, gas phase velocity, and total mass flow rate for two-phase cryogenic nitrogen flow.
LCLS-II Helium Refrigeration System Automation
Authors: Shrishrimal S , Norton R , Keenan M , Robinson D , Fauve E , Ravindranath V , Apte A , Pflueckhahn D , Vyawahare S , Rama B , Pucci J , Creel J
Published: July 2024

SLAC National Accelerator Laboratory has upgraded to LCLS-II, featuring a 4 GeV superconducting linear accelerator composed of 37 cryomodules and two large helium refrigeration systems with a cooling capacity of 4 kW at 2.0 K. This paper focuses on the Helium Refrigeration System (HRS) controls and automation. It presents the various automated functions, sequences, control logics and machine protections embedded in the system. It highlights the design choices selected and experiences in integrating and commissioning of LCLS-II Cryogenic control system.
LCLS-II Cryogenic System Instrumentation
Authors: Robinson D. , Shrishrimal S. , Keenan M. , Fauve E. , Pflueckhahn D. , Ravindranath V. , Apte A. , Vyawahare S. , Pucci J. , Wilson A. , Creel J. , Norton R.
Published: July 2024

SLAC National Accelerator Laboratory has upgraded to LCLS-II, featuring a 4 GeV superconducting linear accelerator composed of 37 cryomodules and two large helium refrigeration systems with a cooling capacity of 4 kW at 2.0 K. In this paper, we provide an overview of the instrumentation and controls for the Cryoplant, Cryodistribution, and Cryomodules, spanning from the instruments themselves, to the PLC I/O cards, and finally to the Human-Machine Interface (HMI). We also discuss the best practices and lessons learned during the commissioning process, which contributed to the successful implementation of the instrumentation and controls.
Commissioning of the cryogenic distribution system of the ESS superconducting linac
Authors: Arnold P , Asensi E , Elias N , Fydrych J , Nilsson P , Zhang J , Polinski J , Duthil P , Petersson A
Published: July 2024

The European Spallation Source (ESS) is a neutron-scattering facility being built with extensive international collaboration in Lund, Sweden. An essential part of the project is the linear 2.0 GeV proton accelerator. Its superconducting part is designed to comprise 13 spoke and 30 elliptical cryomodules that are cooled at 2K. The cryogenic distribution system (CDS) connects the refrigeration plant with the cryomodules via multi-transfer lines, individual valveboxes for every cryomodule and an endbox. It is designed, manufactured and installed under the responsibility of two ESS in-kind partners. The CDS for the spoke cryomodules (CDS-SL) is supplied by IJCLab, France, the CDS for the elliptical cryomodules (CDS-EL) is supplied by WUST, Poland. Pre-commissioning, commissioning and operation is done by ESS whereby IFJ PAN contributed with valuable advice. Pre-commissioning activities like loop checks, temperature curve validation, pressure sensor calibration or valve initialization and leak tightness tests followed after mechanical or electrical completion of the respective CDS parts and started in summer 2022. Eventually, the system was ready for commissioning and a first cooldown was performed in December 2022. Goal of this commissioning was to acceptance test and check off the system before pilot cryomodule installation in the tunnel started in March 2023. The paper describes diverse challenges regarding TAO and cryo operation. Test results, lessons learnt, and required modifications are discussed as well as preliminary results of retesting and an outlook.
Integration of a new Cryogenic Liquefier into the IB-1 Cryogenic Test Facility
Authors: Barba Maria , Hansen Benjamin , White Michael , Johnson Gregory , Atassi Omar Al , Dong Jun , Ranpariya Shreya , Soyars William , Faraj Ahmed , Patel Pratik , Besse Noelle , Machefel Annelise , Perrot Lois
Published: July 2024

The increase over the last years of the testing activities related to quantum systems, SRF cavities for the PIP-II and the LCLS-II projects, as well as superconducting magnets for the HL-LHC project and Fusion research activities, has required the addition of a new Helium cryogenic plant into the existing IB-1 Industrial Cryogenic Test Facility. The new cryogenic plant is composed of a cryogenic liquefier (Cold Box) able to provide up to 340 L/h, a 4 kL Dewar and two Mycom® compressors providing up to 120 g/s. AL-AT (Air Liquide Advanced Technologies) has taken part of this project by designing and manufacturing the cryogenic liquefier. This new cryogenic plant is connected through a cryogenic distribution system to a 10 kL Dewar, which is part of the existing cryogenic test facility, itself composed of another Cold Box and a Sullair® compressor. The new cryogenic plant has two main operating modes: one allows to transfer liquid helium at 1.7 bar between the two Dewars, the other allows to transfer supercritical Helium at 2 bar or more between the new Cold Box and the 10 kL Dewar. The entire industrial cryogenic facility is handled by a common Inventory Control System, composed of three control valves, and 9 tanks giving a total buffer volume of more than 1000 m3. This paper presents the technical features of the new Helium cryogenic plant, as well as the main results of the liquefier commissioning phase and details of the helium transfer between the two Dewars, making the connection between the cryogenic plants at the IB-1 Industrial Cryogenic Test Facility.