Pub Date : 2025-12-20DOI: 10.1016/j.cryogenics.2025.104268
Tony John , Rijo Jacob Thomas , K.A. Shafi
Capacitance-based sensors, which are favored for the measurement of void fraction in two-phase cryogenic flow, suffer from low sensitivity and linearity due to the low relative permittivity of cryogens and the non-uniform electric field inside the flow area, respectively. This paper compares the sensitivity and linearity of concave, parallel plate and concentric electrodes for use in capacitance-based void fraction sensors. The simulation model was validated using a concave electrode sensor with stratified flow. The simulation results show that of the three electrode shapes considered, concentric electrodes exhibit excellent sensitivity for both stratified and annular flow regimes and good linearity for stratified flow. Even though they have low sensitivity, the parallel plate electrodes give the best linear behavior between void fraction and capacitance for both flow regimes.
{"title":"Investigation of the effect of electrode configuration on sensitivity and linearity of capacitance-based void fraction sensors for cryogenic nitrogen two-phase flow","authors":"Tony John , Rijo Jacob Thomas , K.A. Shafi","doi":"10.1016/j.cryogenics.2025.104268","DOIUrl":"10.1016/j.cryogenics.2025.104268","url":null,"abstract":"<div><div>Capacitance-based sensors, which are favored for the measurement of void fraction in two-phase cryogenic flow, suffer from low sensitivity and linearity due to the low relative permittivity of cryogens and the non-uniform electric field inside the flow area, respectively. This paper compares the sensitivity and linearity of concave, parallel plate and concentric electrodes for use in capacitance-based void fraction sensors. The simulation model was validated using a concave electrode sensor with stratified flow. The simulation results show that of the three electrode shapes considered, concentric electrodes exhibit excellent sensitivity for both stratified and annular flow regimes and good linearity for stratified flow. Even though they have low sensitivity, the parallel plate electrodes give the best linear behavior between void fraction and capacitance for both flow regimes.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"154 ","pages":"Article 104268"},"PeriodicalIF":2.1,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145799293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-19DOI: 10.1016/j.cryogenics.2025.104269
Zuhua Chen , Jiahao Gao , Xinqi Zheng , Guochun Zhang , Lei Xi , Zhenxing Li , Shilin Yu , Heng Tu , Jun Shen , Shouguo Wang
Magnetic refrigeration technology is one of the important technologies to realize sub-Kelvin temperature environment, in which magnetocaloric materials are of great importance. Polycrystalline powder of β’-Gd2(MoO4)3 was prepared by solid-phase synthesis, and the structure as well as magnetic properties were further investigated. The thermomagnetic curves show that the magnetic ordering temperature is about 0.6 K for β’-Gd2(MoO4)3. The maximum magnetic entropy change of β’-Gd2(MoO4)3 was calculated to be 20.7 and 34.1J kg−1·K−1 under the magnetic field changes from 0 to 1 T and 2 T, respectively. Moreover, the magnetic entropy change curves of β’-Gd2(MoO4)3 at low field have obvious platform-like characteristic, which allows it to act as a refrigerant for wide refrigeration temperature range, thereby improving the overall heat transfer efficiency of the system. These properties make β’-Gd2(MoO4)3 a powerful candidate of magnetic refrigeration materials in the sub-Kelvin temperature cooling.
{"title":"β’-Gd2(MoO4)3: A promising candidate in the sub-Kelvin temperature region","authors":"Zuhua Chen , Jiahao Gao , Xinqi Zheng , Guochun Zhang , Lei Xi , Zhenxing Li , Shilin Yu , Heng Tu , Jun Shen , Shouguo Wang","doi":"10.1016/j.cryogenics.2025.104269","DOIUrl":"10.1016/j.cryogenics.2025.104269","url":null,"abstract":"<div><div>Magnetic refrigeration technology is one of the important technologies to realize sub-Kelvin temperature environment, in which magnetocaloric materials are of great importance. Polycrystalline powder of β’-Gd<sub>2</sub>(MoO<sub>4</sub>)<sub>3</sub> was prepared by solid-phase synthesis, and the structure as well as magnetic properties were further investigated. The thermomagnetic curves show that the magnetic ordering temperature is about 0.6 K for β’-Gd<sub>2</sub>(MoO<sub>4</sub>)<sub>3</sub>. The maximum magnetic entropy change of β’-Gd<sub>2</sub>(MoO<sub>4</sub>)<sub>3</sub> was calculated to be 20.7 and 34.1J kg<sup>−1</sup>·K<sup>−1</sup> under the magnetic field changes from 0 to 1 T and 2 T, respectively. Moreover, the magnetic entropy change curves of β’-Gd<sub>2</sub>(MoO<sub>4</sub>)<sub>3</sub> at low field have obvious platform-like characteristic, which allows it to act as a refrigerant for wide refrigeration temperature range, thereby improving the overall heat transfer efficiency of the system. These properties make β’-Gd<sub>2</sub>(MoO<sub>4</sub>)<sub>3</sub> a powerful candidate of magnetic refrigeration materials in the sub-Kelvin temperature cooling.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"154 ","pages":"Article 104269"},"PeriodicalIF":2.1,"publicationDate":"2025-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145838755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-17DOI: 10.1016/j.cryogenics.2025.104259
Hiroki Fujii
Ex situ processed Fe-sheathed tapes using a mixture of MgB2 and Sn powders milled for 30 and 100 h were sintered at 410 – 710 ℃ under hydrogen partial pressures of 0, 5, 20, 50 and 100 kPa in a gas mixture of Ar and H2. The filling powders were pure MgB2 and the mixture with the addition of 3.7 wt% Sn. Without addition of Sn, tapes sintered under a pure H2 atmosphere show well-connected structure of grains in the core or improved grain connectivity in microstructure compared to tapes sintered under a pure Ar atmosphere. The undoped tapes sintered at 680 ℃ under pure Ar or 530 ℃ under pure H2 exhibit transport critical current density (Jc) values of approximately 150 A/mm2 at 4.2 K and 10 T. Therefore, sintering under pure H2 is effective in reducing the sintering temperature. The sintering temperature of 530 ℃ is lower than the melting point of lightweight Al, which is one of the candidates for sheath materials for MgB2 conductors, which is 660 ℃. Regarding the control of hydrogen partial pressure, the critical temperature (Tc) of the tapes increases by up to 2 K as the hydrogen partial pressure increases. However, the transport Jc values at 4.2 K and 10 T of these tapes sintered in a flow of mixed gas of Ar and H2 do not improve compared to those sintered under pure H2. Thus, sintering under pure H2 is the most effective in the improvement in Tc and transport Jc. Whereas Sn addition is effective in shifting the transport Jc versus sintering temperature curves to a lower sintering temperature under pure Ar, the addition brings about neither such a shift nor transport Jc enhancement under pure H2. These results lead to the fabrication of lightweight Al-sheathed conductors for applications such as maglev trains.
{"title":"Low-temperature sintering of ex situ processed MgB2 tapes under various hydrogen partial pressures","authors":"Hiroki Fujii","doi":"10.1016/j.cryogenics.2025.104259","DOIUrl":"10.1016/j.cryogenics.2025.104259","url":null,"abstract":"<div><div>Ex situ processed Fe-sheathed tapes using a mixture of MgB<sub>2</sub> and Sn powders milled for 30 and 100 h were sintered at 410<!--> <!-->–<!--> <!-->710 ℃ under hydrogen partial pressures of 0, 5, 20, 50 and 100 kPa in a gas mixture of Ar and H<sub>2</sub>. The filling powders were pure MgB<sub>2</sub> and the mixture with the addition of 3.7 wt% Sn. Without addition of Sn, tapes sintered under a pure H<sub>2</sub> atmosphere show well-connected structure of grains in the core or improved grain connectivity in microstructure compared to tapes sintered under a pure Ar atmosphere. The undoped tapes sintered at 680<!--> <!-->℃ under pure Ar or 530<!--> <!-->℃ under pure H<sub>2</sub> exhibit transport critical current density (<em>J</em><sub>c</sub>) values of approximately 150 A/mm<sup>2</sup> at 4.2 K and 10 T. Therefore, sintering under pure H<sub>2</sub> is effective in reducing the sintering temperature. The sintering temperature of 530<!--> <!-->℃ is lower than the melting point of lightweight Al, which is one of the candidates for sheath materials for MgB<sub>2</sub> conductors, which is 660<!--> <!-->℃. Regarding the control of hydrogen partial pressure, the critical temperature (<em>T</em><sub>c</sub>) of the tapes increases by up to 2 K as the hydrogen partial pressure increases. However, the transport <em>J</em><sub>c</sub> values at 4.2 K and 10 T of these tapes sintered in a flow of mixed gas of Ar and H<sub>2</sub> do not improve compared to those sintered under pure H<sub>2</sub>. Thus, sintering under pure H<sub>2</sub> is the most effective in the improvement in <em>T</em><sub>c</sub> and transport <em>J</em><sub>c</sub>. Whereas Sn addition is effective in shifting the transport <em>J</em><sub>c</sub> versus sintering temperature curves to a lower sintering temperature under pure Ar, the addition brings about neither such a shift nor transport <em>J</em><sub>c</sub> enhancement under pure H<sub>2</sub>. These results lead to the fabrication of lightweight Al-sheathed conductors for applications such as maglev trains.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"154 ","pages":"Article 104259"},"PeriodicalIF":2.1,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145799292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-16DOI: 10.1016/j.cryogenics.2025.104266
Jiameng Xu, Fuyu Yang, Yikun Zhang, Xinyu Zhao, Zhe Kong
The low-temperature magnetocaloric (MC) performances in rare-earth (RE)-based magnetic materials have been determined intensively which are aimed to explore suitable materials for magnetic refrigeration (MR) application. In this work, we synthesized the Tb2Zr2O7 compound using solid-state reaction method and characterized its crystal structure, elemental valence states, magnetism, and low-temperature MC properties. The Tb2Zr2O7 compound crystallizes in a fluorite-type cubic structure and orders magnetically around the temperature of 2.2 K. The consistent elements are all distributed uniformly and presented as Tb3+, Zr4+, and O2– valence states, respectively. Prominent low-temperature MC performances have been realized in Tb2Zr2O7 compound which were related to its second order type magnetic phase transition. The MC parameters of maximum magnetic entropy change and refrigerant capacity for Tb2Zr2O7 compound under magnetic field variation of 0–7 T reach 11.8 J/kg·K and 192.2 J/kg, respectively. These MC parameters are comparable with some recently reported RE-based high-performing MC materials, making the Tb2Zr2O7 compound may also considerable for low-temperature MR applications.
{"title":"Magnetic properties and low-temperature magnetocaloric performances in fluorite-type Tb2Zr2O7 compound","authors":"Jiameng Xu, Fuyu Yang, Yikun Zhang, Xinyu Zhao, Zhe Kong","doi":"10.1016/j.cryogenics.2025.104266","DOIUrl":"10.1016/j.cryogenics.2025.104266","url":null,"abstract":"<div><div>The low-temperature magnetocaloric (MC) performances in rare-earth (<em>RE</em>)-based magnetic materials have been determined intensively which are aimed to explore suitable materials for magnetic refrigeration (MR) application. In this work, we synthesized the Tb<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> compound using solid-state reaction method and characterized its crystal structure, elemental valence states, magnetism, and low-temperature MC properties. The Tb<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> compound crystallizes in a fluorite-type cubic structure and orders magnetically around the temperature of 2.2 K. The consistent elements are all distributed uniformly and presented as Tb<sup>3+</sup>, Zr<sup>4+</sup>, and O<sup>2–</sup> valence states, respectively. Prominent low-temperature MC performances have been realized in Tb<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> compound which were related to its second order type magnetic phase transition. The MC parameters of maximum magnetic entropy change and refrigerant capacity for Tb<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> compound under magnetic field variation of 0–7 T reach 11.8 J/kg·K and 192.2 J/kg, respectively. These MC parameters are comparable with some recently reported <em>RE</em>-based high-performing MC materials, making the Tb<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> compound may also considerable for low-temperature MR applications.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"154 ","pages":"Article 104266"},"PeriodicalIF":2.1,"publicationDate":"2025-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-16DOI: 10.1016/j.cryogenics.2025.104265
Chuanyi Zhao , Huan Jin , Guanyu Xiao , Le Wang , Peng Gao , Chao Zhou , Jinggang Qin
The REBCO conductor on round core (CORC) cable, featuring high mechanical strength and high current density, has emerged as the preferred option for high-field superconducting magnets. Considering economic and safety factors, the large-scale nested superconducting magnets wound from these cables are designed to adopt demountable lap joints to realize electrical connections between sub-coils. This study focuses on comparing lap joints based on the REBCO CORC cable prepared from different materials, and testing their performance at 77 K and self-field. The results indicate that the deformable fine indium wires used as the inserts results in the lowest resistance of the REBCO CORC lap joints. Moreover, the resistivity of the connecting material is not the only factor affecting the performance of the lap joints, the material adhesion effect on the joint surface and the thickness of the material are also related to the performance of the lap joints. The conclusions are informative for the development of large aperture nested REBCO CORC magnets.
{"title":"Effects of connection conditions on lap joint performance in REBCO CORC cables","authors":"Chuanyi Zhao , Huan Jin , Guanyu Xiao , Le Wang , Peng Gao , Chao Zhou , Jinggang Qin","doi":"10.1016/j.cryogenics.2025.104265","DOIUrl":"10.1016/j.cryogenics.2025.104265","url":null,"abstract":"<div><div>The REBCO conductor on round core (CORC) cable, featuring high mechanical strength and high current density, has emerged as the preferred option for high-field superconducting magnets. Considering economic and safety factors, the large-scale nested superconducting magnets wound from these cables are designed to adopt demountable lap joints to realize electrical connections between sub-coils. This study focuses on comparing lap joints based on the REBCO CORC cable prepared from different materials, and testing their performance at 77 K and self-field. The results indicate that the deformable fine indium wires used as the inserts results in the lowest resistance of the REBCO CORC lap joints. Moreover, the resistivity of the connecting material is not the only factor affecting the performance of the lap joints, the material adhesion effect on the joint surface and the thickness of the material are also related to the performance of the lap joints. The conclusions are informative for the development of large aperture nested REBCO CORC magnets.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"153 ","pages":"Article 104265"},"PeriodicalIF":2.1,"publicationDate":"2025-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145786873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-15DOI: 10.1016/j.cryogenics.2025.104267
Wei Zhou , Zhihua Zhang , Weiwei Zhang , Wei Liu , Donghui Liu
The racetrack NbTi superconducting coil is a critical component for high-field magnet applications especially maglev trains, yet its stable operation at 4.2 K presents significant challenges under mechanical and electromagnetic loads. The frictional heat generated at internal contact interfaces poses a particular threat to thermal stability, potentially leading to quench. This paper develops a sequential multiscale framework to investigate the coupled thermo-mechanical responses of the coil. A microscopic representative volume element (RVE) of the NbTi strand is established and homogenized to derive equivalent orthotropic properties, which are applied in the macroscopic finite element model of the racetrack coil. The coupled analysis is performed considering different contact settings under both external pressure and electromagnetic force loading conditions. The study highlights that internal strand contacts cause evident increase in local contact pressure and temperature, with the latter rising to 26.5 K under pressure loading condition, far exceeding the NbTi critical temperature. The critical contact pressure threshold is identified, beyond which rapid temperature escalation occurs. The temperature dependence is also discussed to evaluate the material variation. The proposed method provides an effective tool for assessing the multiscale thermo-mechanical behavior of superconducting coils and offers valuable insights for magnet design and stability optimization.
{"title":"Coupled thermo-mechanical analysis of racetrack NbTi superconducting coil under pressures and electromagnetic forces","authors":"Wei Zhou , Zhihua Zhang , Weiwei Zhang , Wei Liu , Donghui Liu","doi":"10.1016/j.cryogenics.2025.104267","DOIUrl":"10.1016/j.cryogenics.2025.104267","url":null,"abstract":"<div><div>The racetrack NbTi superconducting coil is a critical component for high-field magnet applications especially maglev trains, yet its stable operation at 4.2 K presents significant challenges under mechanical and electromagnetic loads. The frictional heat generated at internal contact interfaces poses a particular threat to thermal stability, potentially leading to quench. This paper develops a sequential multiscale framework to investigate the coupled thermo-mechanical responses of the coil. A microscopic representative volume element (RVE) of the NbTi strand is established and homogenized to derive equivalent orthotropic properties, which are applied in the macroscopic finite element model of the racetrack coil. The coupled analysis is performed considering different contact settings under both external pressure and electromagnetic force loading conditions. The study highlights that internal strand contacts cause evident increase in local contact pressure and temperature, with the latter rising to 26.5 K under pressure loading condition, far exceeding the NbTi critical temperature. The critical contact pressure threshold is identified, beyond which rapid temperature escalation occurs. The temperature dependence is also discussed to evaluate the material variation. The proposed method provides an effective tool for assessing the multiscale thermo-mechanical behavior of superconducting coils and offers valuable insights for magnet design and stability optimization.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"153 ","pages":"Article 104267"},"PeriodicalIF":2.1,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145786872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-13DOI: 10.1016/j.cryogenics.2025.104262
Yanpi Lin , Jiahao Xu , Desheng Lin , Xiaojun Li , Zuchao Zhu
As a key component of the aviation propellant supply system, the liquid oxygen (LO2) pump has characteristics of cryogenic and high oxidizing properties. With the development of aviation propulsion technology, performance requirements for LO2 pump have shifted from a focus on high pressure ratio to the need for lightweight design, high reliability, and wide operational adaptability. This study has developed an integrated electric LO2 pump with a wide flow adjustment capability of 1:20. The pump eliminates the mechanical seal structure and it is driven by a cryogenic, high-speed permanent magnet motor, with the pump and motor arranged coaxially, which achieves small axial length, light weight and high reliability. The motor rotor is directly immersed in the medium, allowing the medium to lubricate and cool the motor bearings. A shielding sleeve is installed on the inner wall of the motor stator to completely isolate the stator from the medium and achieve leakage free. This study can provide technical support for the application of integrated high-speed electric liquid oxygen pump technology in the aviation field.
{"title":"Development of an integrated electric LO2 pump with wide operational adaptability","authors":"Yanpi Lin , Jiahao Xu , Desheng Lin , Xiaojun Li , Zuchao Zhu","doi":"10.1016/j.cryogenics.2025.104262","DOIUrl":"10.1016/j.cryogenics.2025.104262","url":null,"abstract":"<div><div>As a key component of the aviation propellant supply system, the liquid oxygen (LO<sub>2</sub>) pump has characteristics of cryogenic and high oxidizing properties. With the development of aviation propulsion technology, performance requirements for LO<sub>2</sub> pump have shifted from a focus on high pressure ratio to the need for lightweight design, high reliability, and wide operational adaptability. This study has developed an integrated electric LO<sub>2</sub> pump with a wide flow adjustment capability of 1:20. The pump eliminates the mechanical seal structure and it is driven by a cryogenic, high-speed permanent magnet motor, with the pump and motor arranged coaxially, which achieves small axial length, light weight and high reliability. The motor rotor is directly immersed in the medium, allowing the medium to lubricate and cool the motor bearings. A shielding sleeve is installed on the inner wall of the motor stator to completely isolate the stator from the medium and achieve leakage free. This study can provide technical support for the application of integrated high-speed electric liquid oxygen pump technology in the aviation field.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"153 ","pages":"Article 104262"},"PeriodicalIF":2.1,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145786875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The reliable utilization of structural alloys at cryogenic temperatures is limited by discontinuous plastic flow (DPF), a phenomenon that induces strain localization and compromises mechanical stability. This study examines the DPF behavior of 316LN stainless steel at 20 K across a range of quasi-static strain rates (3 × 10−5 to 6 × 10−4 s−1) using a cryocooler environment. By integrating digital image correlation (DIC) with an elastoplastic constitutive model optimized via the Newton-Raphson method, this study quantitatively resolved the transient two-dimensional (2D) stress and strain fields on the specimen surface. The results identify two distinct DPF regimes: at higher strain rates within the quasi-static range, thermal accumulation moderates the flow stress, leading to gradual stress decay and transient strain localization. Conversely, at lower rates, the conditions promote abrupt stress drops accompanied by the formation of banded strain structures that impart lasting mechanical heterogeneity. This work establishes a correlation between strain rate, thermal dissipation, and DPF morphology, thereby providing a foundational framework for predicting and mitigating unstable flow in cryogenic applications.
{"title":"Characterizing strain-rate effects on discontinuous plastic flow in 316LN via digital image correlation with cryocooler cooling","authors":"Liancheng Xie , Shanshan Wu , Zhen Geng , Jijun Xin , Zhiyuan Liang , Linjie Zhang , Bixi Li , Zichun Huang , Hengcheng Zhang , Hao Zhang , Wei Wang , Fuzhi Shen","doi":"10.1016/j.cryogenics.2025.104264","DOIUrl":"10.1016/j.cryogenics.2025.104264","url":null,"abstract":"<div><div>The reliable utilization of structural alloys at cryogenic temperatures is limited by discontinuous plastic flow (DPF), a phenomenon that induces strain localization and compromises mechanical stability. This study examines the DPF behavior of 316LN stainless steel at 20 K across a range of quasi-static strain rates (3 × 10<sup>−5</sup> to 6 × 10<sup>−4</sup> s<sup>−1</sup>) using a cryocooler environment. By integrating digital image correlation (DIC) with an elastoplastic constitutive model optimized via the Newton-Raphson method, this study quantitatively resolved the transient two-dimensional (2D) stress and strain fields on the specimen surface. The results identify two distinct DPF regimes: at higher strain rates within the quasi-static range, thermal accumulation moderates the flow stress, leading to gradual stress decay and transient strain localization. Conversely, at lower rates, the conditions promote abrupt stress drops accompanied by the formation of banded strain structures that impart lasting mechanical heterogeneity. This work establishes a correlation between strain rate, thermal dissipation, and DPF morphology, thereby providing a foundational framework for predicting and mitigating unstable flow in cryogenic applications.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"153 ","pages":"Article 104264"},"PeriodicalIF":2.1,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145786871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-11DOI: 10.1016/j.cryogenics.2025.104263
Lihao Liu , Shuai Zhang , Pengbo Zhou , Zhibo Zhao , Ruichen Wang , Guangtong Ma
No-insulation (NI) high-temperature superconducting (HTS) coils are widely used in many applications because of their higher current density, excellent mechanical properties, and self-protection capability. However, because their current transmission path is not unique, the modeling of NI coils becomes more complex compared to the insulated one. In this paper, we have established a field-circuit coupling model based on the - formulation and validated its accuracy during both transient charging/discharging and external magnetic field exposures. The results indicate that the proposed model is capable of effectively characterizing the overall behavior and local characteristics of the NI HTS coils. Specifically, the local properties are validated against AC loss measurements under external alternating magnetic fields. Based on the developed model, a small-scale pancake NI coil was fabricated to investigate the factors governing the AC losses in such small pancake coils under both radial and axial background magnetic fields with DC transport current. Results reveal that axial fields induce significantly higher AC losses in NI coils compared to radial fields. Notably, under radial magnetic fields, the loss patterns of NI coils exhibit negligible differences from those of insulated coils. These insights contribute to magnetic field configuration optimization and loss management in NI coil applications.
{"title":"AC losses characterization of current-carrying NI HTS coils under radial and axial magnetic fields by a field-circuit coupled model","authors":"Lihao Liu , Shuai Zhang , Pengbo Zhou , Zhibo Zhao , Ruichen Wang , Guangtong Ma","doi":"10.1016/j.cryogenics.2025.104263","DOIUrl":"10.1016/j.cryogenics.2025.104263","url":null,"abstract":"<div><div>No-insulation (NI) high-temperature superconducting (HTS) coils are widely used in many applications because of their higher current density, excellent mechanical properties, and self-protection capability. However, because their current transmission path is not unique, the modeling of NI coils becomes more complex compared to the insulated one. In this paper, we have established a field-circuit coupling model based on the <span><math><mrow><mi>J</mi></mrow></math></span>-<span><math><mrow><mi>A</mi></mrow></math></span> formulation and validated its accuracy during both transient charging/discharging and external magnetic field exposures. The results indicate that the proposed model is capable of effectively characterizing the overall behavior and local characteristics of the NI HTS coils. Specifically, the local properties are validated against AC loss measurements under external alternating magnetic fields. Based on the developed model, a small-scale pancake NI coil was fabricated to investigate the factors governing the AC losses in such small pancake coils under both radial and axial background magnetic fields with DC transport current. Results reveal that axial fields induce significantly higher AC losses in NI coils compared to radial fields. Notably, under radial magnetic fields, the loss patterns of NI coils exhibit negligible differences from those of insulated coils. These insights contribute to magnetic field configuration optimization and loss management in NI coil applications.</div></div>","PeriodicalId":10812,"journal":{"name":"Cryogenics","volume":"153 ","pages":"Article 104263"},"PeriodicalIF":2.1,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145786876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-11DOI: 10.1016/j.cryogenics.2025.104241
Erick Moreno Resendiz , Nikhil Dani , Prasanna Jayaramu , Sarada Kuravi , Vimal Chaitanya , Mark Zagarola , Edgar R. Canavan , Krishna Kota
A theoretical framework has been developed for designing printed circuit-type heat exchangers (PCHE) used for heat recuperation in DC-type space cryocoolers. Unlike conventional recuperative heat exchanger (RHEX) models, this new approach comprehensively integrates all the design considerations of thermal, fluid, structural and size, weight, and power (SWaP) within a broad design space. In addition, it uniquely evaluates performance using three key design criteria: effectiveness, entropy generation, and the goodness factor, which were typically treated in isolation in prior models. The model has been validated against existing experimental data for heat exchangers and focuses on optimizing the RHEX’s geometric parameters—the channel length, width, height, and number—to maximize heat transfer while minimizing pressure drop, all within stringently defined design thresholds of a state-of-the-art reverse Brayton cryocooler. From an effectiveness standpoint, the optimal design favors fewer but longer channels, increasing heat transfer area, and reducing axial wall conduction. In contrast, minimizing entropy generation leads to a design with an increased number of shorter channels, which lowers the mass flow rate per channel and associated pressure drop. However, the goodness factor is mainly influenced by the aspect ratio of the channel rather than the absolute dimensions. Ultimately, the study reveals the following: (1) it is important to simultaneously include all of the design considerations for proper design and (2) optimizing for all three design criteria simultaneously is inherently challenging. As a result, RHEX design must prioritize the most relevant performance metric based on the specific requirements of the intended application instead of randomly choosing either effectiveness, entropy generation, or goodness factor as the guiding metric. The physical reasons behind the findings are also discussed.
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