bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cities as carbon sinks—classification of wooden buildings
Authors: Amiri Ali , Ottelin Juudit , Sorvari Jaana , Junnila Seppo 
Published: June 2020

Abstract
Although buildings produce a third of greenhouse gas emissions, it has been suggested that they might be one of the most cost-effective climate change mitigation solutions. Among building materials, wood not only produces fewer emissions according to life-cycle assessment but can also store carbon. This study aims to estimate the carbon storage potential of new European buildings between 2020 and 2040. While studies on this issue exist, they mainly present rough estimations or are based on a small number of case studies. To ensure a reliable estimation, 50 different case buildings were selected and reviewed. The carbon storage per m2 of each case building was calculated and three types of wooden buildings were identified based on their carbon storage capacity. Finally, four European construction scenarios were generated based on the percentage of buildings constructed from wood and the type of wooden buildings. The annual captured CO2 varied between 1 and 55 Mt, which is equivalent to between 1% and 47% of CO2 emissions from the cement industry in Europe. This study finds that the carbon storage capacity of buildings is not significantly influenced by the type of building, the type of wood or the size of the building but rather by the number and the volume of wooden elements used in the structural and non-structural components of the building. It is recommended that policymakers aiming for carbon-neutral construction focus on the number of wooden elements in buildings rather than more general indicators, such as the amount of wood construction, or even detailed indirect indicators, such as building type, wood type or building size. A practical scenario is proposed for use by European decision-makers, and the role of wood in green building certification is discussed.
A coupled Temperley–Lieb algebra for the superintegrable chiral Potts chain
Authors: Adderton Remy , Batchelor Murray T , Wedrich Paul 
Published: June 2020

Abstract
The Hamiltonian of the N-state superintegrable chiral Potts (SICP) model is written in terms of a coupled algebra defined by N − 1 types of Temperley–Lieb generators. This generalises a previous result for N = 3 obtained by Fjelstad and Månsson (2012 J. Phys. A: Math. Theor.
45 155208). A pictorial representation of a related coupled algebra is given for the N = 3 case which involves a generalisation of the pictorial presentation of the Temperley–Lieb algebra to include a pole around which loops can become entangled. For the two known representations of this algebra, the N = 3 SICP chain and the staggered spin-1/2 XX chain, closed (contractible) loops have weight

3

and weight 2, respectively. For both representations closed (non-contractible) loops around the pole have weight zero. The pictorial representation provides a graphical interpretation of the algebraic relations. A key ingredient in the resolution of diagrams is a crossing relation for loops encircling a pole which involves the parameter ρ = e
2πi/3 for the SICP chain and ρ = 1 for the staggered XX chain. These ρ values are derived assuming the Kauffman bracket skein relation.
Robotic Refueling Mission-3—an overview
Authors: Breon S R , Boyle R F , Francom M B , DeLee C H , Francis J J , Mustafi S , Barfknecht P W , McGuire J M , Krenn A G , Zimmerli G A , Hauser D M 
Published: June 2020

Abstract
Robotic Refueling Mission-3 (RRM3) is an external payload on the International Space Station (ISS) to demonstrate the techniques for storing and transferring a cryogenic fuel on orbit. RRM3 was designed and built at the National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC). Initial testing was performed at GSFC using liquid nitrogen and liquid argon. Final testing and flight fill of methane was performed at the NASA Kennedy Space Center (KSC) to take advantage of KSC’s facilities and expertise for handling a combustible cryogen. This paper gives an overview of the process and challenges of developing the payload and the results of its on-orbit performance.
Integrated refrigeration and storage of LNG for compositional stability
Authors: Rose L , Swanger A M , Notardonato W U , Fesmire J E , Gleeson J , Carro R 
Published: June 2020

Abstract
Growing interest in liquefied natural gas (LNG) as a rocket fuel necessitates a greater technical understanding of the compositional changes due to preferential boil-off (or weathering) that occurs during long duration storage. The purity of methane in LNG can range from 90 to 98%, and is subject to preferential boil-off due to its low boiling point compared to other constituents despite the use of high-performance thermal insulation systems. Active heat extraction (i.e. refrigeration) is required to completely eliminate weathering. For future operational safety and reliability, and to better understand the quality and efficiency of the LNG as a cryofuel, a 400-liter Cryostat vessel was designed and constructed to measure the composition and temperatures of the LNG at a number of different liquid levels over long durations. The vessel is the centerpiece of a custom-designed lab-scale integrated refrigeration and storage (IRaS) system employing a pulse tube cryocooler capable of roughly 50 W of lift at 100 K. Instrumentation includes ten temperature sensors mounted on a vertical rake and five liquid sample tubes corresponding to five liquid levels. Two modes of operation are studied. The first is without refrigeration in order to determine a baseline in the change in composition, and to study stratification of the LNG. The second is performed with the cryocooler active to determine the operational parameters of the IRaS system for eliminating the weathering as well as stratification effects in the bulk liquid. The apparatus design and test method, as well as preliminary test results are presented in this paper. As a bonus in cost-saving and operational efficiency, the capability of the IRaS system to provide zero-loss capabilities such as zero boil-off (ZBO) keeping of the LNG and zero-loss filling/transfer operations are also discussed.
Performance characteristics comparison of major types of mechanical cryocoolers for aerospace applications
Authors: Chen W 
Published: June 2020

Abstract
The three major types of mechanical cryocoolers in aerospace applications, namely reverse-Brayton cryocoolers, Stirling/pulse tube cryocoolers and Joule-Thomson cryocoolers, have significantly different performance characteristics. Some of these differences are due to the nature of their thermodynamic cycles; others come from their drastic differences in mean operating pressures and pressure ratios. This paper first provides an overview of the performance characteristics of these three types of cryocoolers, their unique performance benefits and main applications. It then derives an analytical expression for a cryocooler’s Carnot efficiency, considering the effects of the system pressure ratio drop from the warm end to the cold end and heat leak due to the convective flow and axial conduction. The convective heat leak is related to the pressure drop and the figure of merit of the heat transfer surface using the Colburn-Chilton analogy. Based on this result, the paper discusses the key control parameters affecting the size and mass of the heat exchanger and thus the overall cooler system in each type of cryocooler.
Impact of the cold regenerator mesh geometry on low temperature pulse tube cold finger performance
Authors: Dherbécourt D , Martin S , Charles I , Duval JM , André J , Daniel C 
Published: June 2020

Abstract
Future astrophysics missions such as SPICA, Athena or LiteBird will need a cooling below 1 K (until 50 mK) to achieve the detectors’ required sensibility. To address such requirements, cooling chains are built coupling several technologies using intermediate temperature cooling, explaining why a high cooling power at 15 K is essential. The CEA-DSBT designed, for lab test purpose, a Pulse Tube cooler system consisting of a heat intercepted single-stage cold finger which is pre-cooled by a Gifford McMahon cryocooler. The cold part of the PT, in particular the regenerator, is critical to the PT cooler performance. Keeping the regenerator material standard (stainless steel mesh), we study here the influence of the cold regenerator mesh geometry on the operation of the cold finger. The wire thickness is varied, which modifies the porosity, the dead volume and the heat surface exchange of the regenerator. Experimental results on different mesh designs are presented here and analysed, showing a significant influence of the mesh geometry on the performance.
Modifications to the MIRI cryocooler design to provide significant lift in the 2K to 4K range
Authors: Petach M , Michaelian M , Nguyen T 
Published: June 2020

Abstract
A high Technology Readiness Level cryocooler with significant cooling in the 2K to 4K regime will enable a variety of missions ranging from large infrared space telescopes to superconducting and quantum applications. The cryocooler for the MIRI instrument on JWST was designed for operation at 6K, and with relatively minor changes this design can achieve significant lift in the 2K to 4K region. This paper provides curves of predicted lift vs. power for a variety of operating temperatures, based on the model anchored by tests of the MIRI cooler. The modifications are described, and their mass impacts are estimated. These mass and performance estimates enable payload and mission planners to explore new mission classes.
Return to service of a liquid hydrogen storage sphere
Authors: Krenn A , Desenberg D 
Published: June 2020

Abstract
One, of two, 850,000 gallon liquid hydrogen storage spheres, at NASA’s Kennedy Space Center, was decommissioned in 2010. This tank had an abnormally high heat leak that was investigated and determined to be the result of a large void in the perlite insulation. The insulation void was subsequently filled, and the tank was refurbished for its planned use in the Space Launch Systems (SLS) program. Return to service of this tank began in December of 2017 with a partial liquid hydrogen fill. Since that time, routine measurement of the liquid level have been recorded in order to establish a new boiloff rate and associated heat leak. This data shows the perlite top off activities have resulted in a much reduced, and within design specification, heat leak.
Experimental Study on Pool Boiling Heat Transfer Characteristics of Slush Nitrogen
Authors: Wu S Q , Wang Q D , Li Y J , Huang J L , Jin T 
Published: June 2020

Abstract
Slush nitrogen is a cryogenic two-phase fluid with solid nitrogen particles suspended in liquid nitrogen, which can be a potential coolant for high temperature superconductor thanks to its high density and large heat capacity. The present work focuses on the pool boiling heat transfer characteristics of slush nitrogen. The freeze-thaw method was used to produce slush nitrogen and the capacitance-type density meter was adopted to determine the solid volumetric fraction of slush nitrogen. The experimental results show that the heat transfer characteristics of slush nitrogen matches with typical nucleate boiling heat transfer. The heat transfer of slush nitrogen can be enhanced by increasing the solid fraction. The applicability of Rohsenow equation to the nucleate pool boiling heat transfer of slush nitrogen was analyzed, and then a heat transfer correlation for nucleate pool boiling heat transfer of liquid nitrogen and slush nitrogen, considering the effect of solid volumetric fraction, was summarized.
A novel hydrogen turbo-expander with active magnetic bearings and an eddy current brake
Authors: Chen J Y , Li X M , Dong X B , Lv C , Wu J H 
Published: June 2020

Abstract
A cryogenic expander for hydrogen liquefier with active magnetic bearings (AMB) has been designed and will be made and tested. The shaft design and strength review are significant factors for the turbine since it affects the performance and safety of the expander significantly. In order to produce lower temperature hydrogen, the liquefier needs a very small and high-speed turbo-expander. However, there are few studies on expander with both active magnetic bearings and eddy current brakes. In this study, the speed of the turbine is up to 100000 rpm. Its cooling power is about 4kW. The inlet pressure is 1MPa, and the outlet pressure is 0.7MPa. Under this condition, the turbine is designed, and the simulation is done. An eddy current brake which can govern the rotational speed quickly is designed and studied as well.
FLIR FL-100 Miniature Linear Stirling Cryocooler Development Summary
Authors: Conrad T , Haley D , Lieb T , Grabau M , Miramontes S , Garcia E , Chapple S , Erwin B 
Published: June 2020

Abstract
FLIR Systems has recently developed and begun manufacturing a miniature linear Stirling cryocooler, the FL-100, which has been designed to meet the needs of compact systems using High Operating Temperature (HOT) detectors. These include low cost, long life, high efficiency, and a very compact packaging size. A compact and efficient drive electronics board, the Cryogenic Cooler Controller (CCC), has also been developed to pair with the FL-100. This paper presents the design specifications of the FL-100 cryocooler and summarizes the results of the testing which has been completed thus far on prototype and early production units.
Investigation of improving cool-down speed of Stirling type pulse tube cryocooler with ambient displacers
Authors: Yan C G , Wang X T , Dai W , Pfotenhauer John M. , Zhang Y B , Li H B , Luo E C 
Published: June 2020

Abstract
For a cryocooler, besides high efficiency at the working temperature, the cool-down speed is also important for some applications. Because of the difference in structure and operating mechanism, different cryocoolers have different characteristics for cool-down speed. This work introduces a Stirling type pulse tube cryocooler with ambient displacers which works in the liquid nitrogen temperature region. Strategies for improving the cool-down speed from room temperature to liquid nitrogen temperature have been investigated through simulation. The pulse tube cryocooler is designed to provide a nominal cooling power of 17.8 W at 77 K with 232.5 W of input electric power at 70 Hz. By fixing the maximum displacer movement in the simulation, the characteristics of how tuning the frequency around 70 Hz can change the cool-down speed without exceeding the allowable displacement of the piston and the current draw of the actual compressor are investigated. The strategy for tuning both the frequency and voltage turns out be effective in the beginning stage of the cool-down process with an improvement of the cooling power by about 15%-20%. The gain becomes less obvious as the cold head temperature drops. In conclusion, tuning both the frequency and voltage during the cool-down process helps the cold-head to reach its final temperature faster but the average gain is not as big as expected.
CFD study of the 2D gas piston in pulse tube cryocoolers
Authors: Guo Zhimin , Zhu Shaowei , Pfotenhauer John M 
Published: June 2020

Abstract
There are three parts of the gas moving through the pulse tube of the pulse tube cryocooler, part I is the gas moving between the cold heat exchanger and the pulse tube, part II is the gas oscillating in the pulse tube all the time, part III is the gas moving between the pulse tube and the warm heat exchanger. The part of the gas that always moves in the pulse tube performs the same function as a solid piston; this part of the gas is called the gas piston. The shape and the position of the gas piston changes with time and the operating conditions rather than remaining fixed. A 1D model cannot capture the change of the gas piston near the wall, but a 2D model capturing changes in the axial and radial directions can. Further, the uniformity of the fluid flow field in the pulse tube can be depicted by the shape of the gas piston which can be simply envisioned as a 2D gas piston in the pulse tube. In this study a CFD method is used to obtain the details of the 2D gas piston. The velocity field in the pulse tube is obtained by the commercial code ANSYS Fluent, and a LaGrange particle tracing method is introduced to process the velocity data in order to obtain the boundary of the 2D gas piston. Additionally, this work investigates the influence of various parameters including pressure ratio, pulse tube aspect ratio and frequency on the shape of the gas piston. It reveals that a larger pressure ratio, larger aspect ratio and lower frequency cause a larger deformation of the gas piston in one cycle. These effects are especially noticeable at the warm end of pulse tube, which displays a larger deformation than other positions in the pulse tube under the influence of changes in those parameters.
Cryogenic Flux Capacitor for Advanced Molecular and Energy Storage Applications
Authors: Swanger A M , Fesmire J E 
Published: June 2020

Abstract
Effective storage and transfer of fluid commodities such as oxygen, hydrogen, natural gas, nitrogen, argon, and others is a necessity in many industries and for hosts of different applications. Molecules are typically contained as low pressure, cryogenic liquids; or as high-pressure gases. Liquefied gasses afford high energy and volume densities, but require complex storage systems to limit boil-off losses, need constant settling in zero-gravity, and are not well suited for overly dynamic situations where the tank orientation can change suddenly. Most cryogenic liquid tanks are complex, nested configurations to increase thermal performance, making them large, massive, and difficult to be made into conformal shapes. Conversely, high pressure gas storage bottles are unaffected by orientation, and can be kept at room temperature; however, these vessels are heavy-walled to contain the high pressures, and the energy densities associated with gas storage are dramatically lower. These two options are typically traded depending on the system requirements, but few practical options exist that provide the benefits while limiting the downfalls. Alternatively, the Cryogenic Flux Capacitor (CFC) technology employs nano-porous aerogel composites to store, by physisorption processes, large quantities of fluid molecules in a molecular solid-state condition, at moderate pressures and cryogenic temperatures. By virtue of its design architecture, a CFC device can be “charged” and “discharged” quickly and on-demand according to operational requirements. Three CFC application areas are introduced: CFC-Fuel, CFC-Cool, and CFC-Life, corresponding to designs utilizing fuels such as hydrogen and methane; inert fluids such as nitrogen and argon for cooling power; and oxygen or breathing air for life support. Data for physisorption within different aerogel composites are presented in terms of both mass and volumetric parameters.
Design of dewar supports through topology optimization
Authors: Nitin B , Sandilya Pavitra , Chakraborty Goutam 
Published: June 2020

Abstract
Dewars are used to store and transport cryogens like LNG, LN2, LOX, LHe etc. These comprise two vessels, one placed inside the other and held together either at the “neck” (input/output port) or by support systems, depending on the capacity, the mechanical loads on the vessel and the boil-off characteristic of the stored cryogen. Support system based dewars are more common for real-life and industrial applications. Design of the support system are based on the principles that are used for high temperature pressure vessels. On the other hand, support system to be used for cryogenic fluid storage should also address the heat inleak through the supports along with the imposed mechanical load and thermal contraction-expansion effects. Some safety factors are prescribed in the literature to address these concerns; however, the scientific basis of design strategies available in the open literature so as to give a more scientific basis of design is absent. This would result in reduction in use of excessive dimensions or material thereby reducing the payload and the capital cost. Considerations of mechanical load and thermal heat inleak often lead to diametric conclusions in terms of the diameter/thickness of the support system, leading to pareto-optimal solution. Topology optimization (TO) is often used to design structures like bridges, vehicles, robotic arms etc. by a systematic and sequential removal of the mass of the material being used to fabricate the given structure while meeting the constraints in terms of load bearing capacity of the structure and heat inleak. This methodology may be followed to arrive at an optimized geometry for the support system when the designer is unsure of the initial shape to start working. In this work, TO has been tested with various thermal and mechanical boundary conditions to arrive at optimized support geometry.
Experimental and numerical investigation of 2 K heat exchanger for superfluid helium cryogenic systems at KEK
Authors: Kumar A , Nakai H , Nakanishi K , Shimizu H , Kojima Y , Hara K , Honma T 
Published: June 2020

Abstract
Superfluid helium cryogenic systems at KEK are constructed for research and development of cryomodules of the compact Energy Recovery Linac (cERL) and the International Linear Collider (ILC). The niobium superconducting radio frequency (SRF) cavities in cERL and ILC operate at temperatures of 2.0 K or below. The SRF cavities are cooled with saturated superfluid helium, which is another phase of the liquid helium (LHe), when it is cooled below 2.17 K under saturation condition. To produce superfluid helium continuously, a Joule-Thomson (JT) valve is employed in the cryogenic system. Also, a 2 K heat exchanger (2K HX) is introduced in series with the JT valve to recover the coldness from 2.0 K gaseous helium (GHe) evaporating from the helium tanks of the SRF cavities. This increases the production rate of superfluid helium by reducing the incoming LHe temperature from 4.4 K to 2.2 K or above before the JT valve. At KEK, we have a 2K HX consisting of a helical coil and laminated fins for thermal loads up to 100 W. Its performance needs to be determined and is characterized by a factor known as effectiveness, which is the ratio of actual heat transfer to the maximum possible heat transfer between the fluids. The performance of the 2K HX has been determined experimentally using the heat exchanger test stand and numerically by computational fluid dynamics (ANSYS CFX®), respectively. In the heat exchanger test stand, the mass flow rate of incoming LHe is kept identical to the outgoing GHe through the 2K HX, using the level and pressure control of superfluid helium. An electric cartridge heater is immersed in the superfluid helium to vary the mass flow rate of evaporating superfluid helium. In the future, the optimization of the 2K HX design will be performed to improve its performance.
Entropy Analysis of Support Systems in Multi-Channel Cryogenic Lines
Authors: Duda P , Chorowski M , Poliński J 
Published: June 2020

Abstract
This work describes the methods for transporting cryogens through multi-channel transfer lines. It also presents examples of the use of cryogenic lines and of their designs, referring in detail to typical structural nodes found in cryogenic transfer lines. The second principle of thermodynamics and the Gouy-Stodola theorem are discussed from the perspective of their application in optimizing and evaluating heat and mass transfer devices. The next part of the work presents the internal structure of the selected 100 m multi-channel cryogenic transfer line. Several variants of the method of supporting process pipes have been presented. For each of the solutions, an entropy analysis was carried out in order to select the best design in terms of the entropy generated in the process pipes.