IOP Conference Series: Materials Science and Engineering, 2020
Various functional insertion components (FIC), directly connecting a cold mass and the ambient en... more Various functional insertion components (FIC), directly connecting a cold mass and the ambient environment, are irreplaceable and play crucial technical roles in many superconducting cryogenic applications. However, such components also bring a huge heat leak to the cold mass. The heat leak is usually much greater than that through entire evacuated MLI insulation system and solid support structures combined. Therefore, this situation brings unimaginable challenges not only to the refrigeration loads to be met but also critical aspects of the FIC design in satisfaction of highly restrictive, even contradicting technical functions. The FIC must simultaneously minimize the heat leak provide a large amounts of DC current and RF power to/from the cold mass, as well as provide a reliable ultrahigh vacuum thermal isolation break with strong mechanical stability. Reviewed are the following commonly used FICs: 1) various RF input couplers for transmitting MW-RF power; 2) high DC power curren...
IOP Conference Series: Materials Science and Engineering, 2020
High temperature superconducting (HTS) power transmission cables are cooled to operating temperat... more High temperature superconducting (HTS) power transmission cables are cooled to operating temperatures typically below 80 K. A valuable feature of some HTS cables is that they can limit short-circuit fault currents, which can be more than ten times the maximum operating current of a cable. When a fault occurs the HTS wire is no longer superconducting and the heating which occurs will raise the temperature above the allowable operating point. To recover from the fault, the conductor must be cooled down before returning to service. The recovery is affected by the refrigeration system’s performance which varies with load and temperature. A transient numerical model of an HTS cable is applied to investigate the thermal recovery after a fault for some HTS cable system configurations and operating conditions.
ArticleinIEEE Transactions on Applied Superconductivity, 2003
The use of high-temperature superconducting (HTS) materials for power transmission cable applicat... more The use of high-temperature superconducting (HTS) materials for power transmission cable applications is being realized in several utility demonstration projects. Both room-temperature and cold-dielectric cable systems rely on a vacuum cryostat to keep the ambient thermal loads at a minimum. For long-term installations, operating 30 years or longer, the thermal-insulating vacuum pressure may increase in sections of a long length installation. Even if only a small section of the total length of the HTS cable system is affected, localized heating of the cable may reduce the performance of the HTS cable system. A study is presented of the effects of degraded vacuum levels on the operation of HTS cables for different cryogenic thermal insulation systems.
IOP Conference Series: Materials Science and Engineering, 2017
Systematic review is given of development of novel heat switches at cryogenic temperatures that a... more Systematic review is given of development of novel heat switches at cryogenic temperatures that alternatively provide high thermal connection or ideal thermal isolation to the cold mass. These cryogenic heat switches are widely applied in a variety of unique superconducting systems and critical space applications. The following types of heat switch devices are discussed: 1) magnetic levitation suspension, 2) shape memory alloys, 3) differential thermal expansion, 4) helium or hydrogen gap-gap, 5) superconducting, 6) piezoelectric, 7) cryogenic diode, 8) magneto-resistive, and 9) mechanical demountable connections. Advantages and limitations of different cryogenic heat switches are examined along with the outlook for future thermal management solutions in materials and cryogenic designs.
Although some standards exist for thermal insulation, few address the sub-ambient temperature ran... more Although some standards exist for thermal insulation, few address the sub-ambient temperature range and cold-side temperatures below 100 K. Standards for cryogenic insulation systems require cryostat testing and data analysis that will allow the development of the tools needed by design engineers and thermal analysts for the design of practical cryogenic systems. Thus, this critically important information can provide reliable data and methodologies for industrial efficiency and energy conservation. Two Task Groups have been established in the area of cryogenic insulation systems Under ASTM International's Committee C16 on Thermal Insulation. These are WK29609
Flexible, vacuum-insulated transfer lines for low-temperature applications have higher thermal lo... more Flexible, vacuum-insulated transfer lines for low-temperature applications have higher thermal losses than comparable rigid lines. Typical flexible piping construction uses corrugated tubes, inner and outer, with a multilayer insulation (MLI) system in the annular space. Experiments on vacuum insulation systems in a flexible geometry were conducted at the Cryogenics Test Laboratory of NASA Kennedy Space Center. The effects of bending were simulated by causing the inner tube to be eccentric with the outer tube. The effects of spacers were simulated in a controlled way by inserting spacer tubes for the length of the cylindrical test articles. Two material systems, standard MLI and a layered composite insulation (LCI), were tested under the full range of vacuum levels using a liquid nitrogen boiloff calorimeter to determine the apparent thermal conductivity (k-value). The results indicate that the flexible piping under simulated bending conditions significantly degrades the thermal performance of the insulation system. These data are compared to standard MLI for both straight and flexible piping configurations. The definition of an overall k-value for actual field installations (k oa fi) is described for use in design and analysis of cryogenic piping systems.
IOP Conference Series: Materials Science and Engineering, 2015
Standards for thermal insulation used in applications between ambient and low temperatures, below... more Standards for thermal insulation used in applications between ambient and low temperatures, below 100 K, require test data under relevant conditions and by different laboratories to develop data sets for the proper comparisons of materials. This critically important technology is needed to provide reliable data and methodologies for industrial energy efficiency and energy conservation. Under ASTM International's Committee C16 on Thermal Insulation, two standards have been issued on cryogenic thermal insulation systems. Thermal conductivity data sets have been taken using identical flat-plate boiloff calorimeter instruments independently operated at the Cryogenics Test Laboratory of NASA Kennedy Space Center (KSC) and the Thermal Energy Laboratory of LeTourneau University (LETU). Precision specimens of cellular glass insulation were produced for both laboratories to provide the necessary comparisons to validate the thermal measurements and test methodologies. Additional specimens of commercial cellular glass pipe insulation were tested at LETU to compare with the flat plate results. The test data are discussed in relation to the experimental approach, test methods, and manner of reporting the thermal performance data. This initial Inter-Laboratory Study (ILS) of insulation materials for sub-ambient temperature applications provides a foundation for further ILS work to produce standard data sets for several key commercial materials. 1. Introduction There is a need for standard thermal data for cryogenic insulation materials or standard test methods and instrumentation in this area. Standard test methods are needed to produce standard data for conduction of heat by materials in the sub-ambient temperature range. An initial step has been taken for producing standard thermal data through a preliminary Inter-Laboratory Study (ILS) initiated by NASA Kennedy Space Center and LeTourneau University. A major objective of this initial research is to explore the suitability of new methodologies for producing standard data for effective thermal conductivity (ke(T)) and heat flux (q(T)) for commonly used cryogenic insulation materials. Other objectives of this effort are to pave the way for establishing standard data sets for use by engineers, to develop accepted baselines for the performance of novel materials under development, and to provide technical insight on the nature of low heat flows through low-density materials. Knowledge of the dependence of heat transfer related properties on temperature for materials is extremely important because even materials that are considered homogenous may be complicated when applied in systems having temperature differences of several hundred degrees imposed across its thickness.
IOP Conference Series: Materials Science and Engineering
Systematic review is given of development of novel heat switches at cryogenic temperatures that a... more Systematic review is given of development of novel heat switches at cryogenic temperatures that alternatively provide high thermal connection or ideal thermal isolation to the cold mass. These cryogenic heat switches are widely applied in a variety of unique superconducting systems and critical space applications. The following types of heat switch devices are discussed: 1) magnetic levitation suspension, 2) shape memory alloys, 3) differential thermal expansion, 4) helium or hydrogen gap-gap, 5) superconducting, 6) piezoelectric, 7) cryogenic diode, 8) magneto-resistive, and 9) mechanical demountable connections. Advantages and limitations of different cryogenic heat switches are examined along with the outlook for future thermal management solutions in materials and cryogenic designs.
High-temperature superconducting (HTS) cables that typically operate at temperatures below 80 kel... more High-temperature superconducting (HTS) cables that typically operate at temperatures below 80 kelvin (K) are being developed for power transmission. The practical application of HTS power cables will require the use of flexible piping to contain the cable and the liquid nitrogen coolant. A study of thermal performance of multilayer insulation (MLI) was conducted in geometries representing both rigid and flexible piping. This experimental study performed at the Cryogenics Test Laboratory of NASA Kennedy Space Center provides a framework for the development of cost-effective, efficient thermal insulation systems that will support these long-distance flexible lines containing HTS power cables. The overall thermal performance of the insulation system for a rigid configuration and for a flexible configuration, simulating a flexible HTS power cable, was determined by the steady-state liquid nitrogen boiloff method under the full range of vacuum levels. Two different cylindrically rolled material systems were tested: a standard MLI and a layered composite insulation (LCI). Comparisons of ideal MLI, MLI on rigid piping, and MLI between flexible piping are presented.
The Navy intends to use High Temperature Superconducting Degaussing (HTSDG) coil systems on futur... more The Navy intends to use High Temperature Superconducting Degaussing (HTSDG) coil systems on future Navy platforms. The Navy Metalworking Center (NMC) is leading a team that is addressing cryostat configuration and manufacturing issues associated with fabricating long lengths of flexible, vacuum-jacketed cryostats that meet Navy shipboard performance requirements. The project includes provisions to evaluate the reliability performance, as well as proofing of fabrication techniques. Navy cryostat performance specifications include less than 1 Wm-1 heat loss, 2 MPa working pressure, and a 25-year vacuum life. Cryostat multilayer insulation (MLI) systems developed on the project have been validated using a standardized cryogenic test facility and implemented on 5-meterlong test samples. Performance data from these test samples, which were characterized using both LN 2 boiloff and flow-through measurement techniques, will be presented.
IOP Conference Series: Materials Science and Engineering, 2015
The cooling power consumption in large scale superconducting systems is huge and cryogenic device... more The cooling power consumption in large scale superconducting systems is huge and cryogenic devices used in space applications often require an extremely long cryogen holding time. To economically maintain the device at its operating temperature and minimize the refrigeration losses, high performance of thermal isolation is essential. The radiation from warm surrounding surfaces and conducting heat leaks through supports and penetrations are the dominant heat loads to the cold mass under vacuum condition. The advanced developments in various cryogenic applications to successfully reduce the heat loads through radiation and conduction are briefly and systematically discussed and evaluated in this review paper. These include: (1) thermal Insulation for different applications (foams, perlites, glass bubbles, aerogel and MLI), (2) sophisticated low-heat-leak support (cryogenic tension straps, trolley bars and posts with dedicated thermal intercepts), and (3) novel cryogenic heat switches.
Creare has developed a turbo-Brayton cryocooler for the Air Force that is designed to produce app... more Creare has developed a turbo-Brayton cryocooler for the Air Force that is designed to produce approximately 1 kW of refrigeration at 95 K. The cryocooler is intended to provide cryogenic cooling for an air separation system being developed to produce and store liquid oxygen and liquid nitrogen onboard large aircraft. The oxygen will be used for high-altitude breathing and medical evacuation operations, while the nitrogen will be used to inert the ullage space inside the fuel tanks. The cryocooler utilizes gas bearings in the turbomachines for long life without maintenance, which is a critical requirement for this application. The mass of a flight version of this cryocooler is expected to be around 270 kg, while the input power is expected to be 21 to 25 kW. This paper describes the design and testing of the technology demonstration cryocooler that was constructed to establish the feasibility of the approach. In the future, the cryocooler will be integrated and tested with a distillation column subsystem. Subsequent testing may also be performed in-flight on an Air Force transport aircraft.
Although some standards exist for thermal insulation, few address the sub-ambient temperature ran... more Although some standards exist for thermal insulation, few address the sub-ambient temperature range and cold-side temperatures below 100 K. Standards for cryogenic insulation systems require cryostat testing and data analysis that will allow the development of the tools needed by design engineers and thermal analysts for the design of practical cryogenic systems. Thus, this critically important information can provide reliable data and methodologies for industrial efficiency and energy conservation. Two Task Groups have been established in the area of cryogenic insulation systems Under ASTM International's Committee C16 on Thermal Insulation. These are WK29609 -New Standard for Thermal Performance Testing of Cryogenic Insulation Systems and WK29608 -Standard Practice for Multilayer Insulation in Cryogenic Service. The Cryogenics Test Laboratory of NASA Kennedy Space Center and the Thermal Energy Laboratory of LeTourneau University are conducting Inter-Laboratory Study (ILS) of selected insulation materials. Each lab carries out the measurements of thermal properties of these materials using identical flat-plate boil-off calorimeter instruments. Parallel testing will provide the comparisons necessary to validate the measurements and methodologies. Here we discuss test methods, some initial data in relation to the experimental approach, and the manner reporting the thermal performance data. This initial study of insulation materials for sub-ambient temperature applications is aimed at paving the way for further ILS comparative efforts that will produce standard data sets for several commercial materials. Discrepancies found between measurements will be used to improve the testing and data reduction techniques being developed as part of the future ASTM International standards.
... Edited by Susan Breon, Michael Dipirro, David Glaister, John Hull, Peter Kittel, Vitalij Pech... more ... Edited by Susan Breon, Michael Dipirro, David Glaister, John Hull, Peter Kittel, Vitalij Pecharsky, Ray Radebaugh, Jay Theilacker, Steven Van Sciver, John Weisend II, and Albert Zeller. AIP Conference Proceedings, Vol. 613, 2002. Publication Date: 05/2002. Origin: ADS. ...
High-temperature superconducting (HTS) cables that typically operate at temperatures below 80 kel... more High-temperature superconducting (HTS) cables that typically operate at temperatures below 80 kelvin (K) are being developed for power transmission. The practical application of HTS power cables will require the use of flexible piping to contain the cable and the liquid nitrogen coolant. A study of thermal performance of multilayer insulation (MLI) was conducted in geometries representing both rigid and flexible piping. This experimental study performed at the Cryogenics Test Laboratory of NASA Kennedy Space Center provides a framework for the development of cost-effective, efficient thermal insulation systems that will support these long-distance flexible lines containing HTS power cables. The overall thermal performance of the insulation system for a rigid configuration and for a flexible configuration , simulating a flexible HTS power cable, was determined by the steady-state liquid nitrogen boiloff method under the full range of vacuum levels. Two different cylindrically rolled material systems were tested: a standard MLI and a layered composite insulation (LCI). Comparisons of ideal MLI, MLI on rigid piping, and MLI between flexible piping are presented.
Standards for thermal insulation used in applications between ambient and low temperatures, below... more Standards for thermal insulation used in applications between ambient and low temperatures, below 100 K, require test data under relevant conditions and by different laboratories to develop data sets for the proper comparisons of materials. This critically important technology is needed to provide reliable data and methodologies for industrial energy efficiency and energy conservation. Under ASTM International's Committee C16 on Thermal Insulation, two standards have been issued on cryogenic thermal insulation systems. Thermal conductivity data sets have been taken using identical flat-plate boiloff calorimeter instruments independently operated at the Cryogenics Test Laboratory of NASA Kennedy Space Center (KSC) and the Thermal Energy Laboratory of LeTourneau University (LETU). Precision specimens of cellular glass insulation were produced for both laboratories to provide the necessary comparisons to validate the thermal measurements and test methodologies. Additional specimens of commercial cellular glass pipe insulation were tested at LETU to compare with the flat plate results. The test data are discussed in relation to the experimental approach, test methods, and manner of reporting the thermal performance data. This initial Inter-Laboratory Study (ILS) of insulation materials for sub-ambient temperature applications provides a foundation for further ILS work to produce standard data sets for several key commercial materials. 1. Introduction There is a need for standard thermal data for cryogenic insulation materials or standard test methods and instrumentation in this area. Standard test methods are needed to produce standard data for conduction of heat by materials in the sub-ambient temperature range. An initial step has been taken for producing standard thermal data through a preliminary Inter-Laboratory Study (ILS) initiated by NASA Kennedy Space Center and LeTourneau University. A major objective of this initial research is to explore the suitability of new methodologies for producing standard data for effective thermal conductivity (ke(T)) and heat flux (q(T)) for commonly used cryogenic insulation materials. Other objectives of this effort are to pave the way for establishing standard data sets for use by engineers, to develop accepted baselines for the performance of novel materials under development, and to provide technical insight on the nature of low heat flows through low-density materials. Knowledge of the dependence of heat transfer related properties on temperature for materials is extremely important because even materials that are considered homogenous may be complicated when applied in systems having temperature differences of several hundred degrees imposed across its thickness.
The cooling power consumption in large scale superconducting systems is huge and cryogenic device... more The cooling power consumption in large scale superconducting systems is huge and cryogenic devices used in space applications often require an extremely long cryogen holding time. To economically maintain the device at its operating temperature and minimize the refrigeration losses, high performance of thermal isolation is essential. The radiation from warm surrounding surfaces and conducting heat leaks through supports and penetrations are the dominant heat loads to the cold mass under vacuum condition. The advanced developments in various cryogenic applications to successfully reduce the heat loads through radiation and conduction are briefly and systematically discussed and evaluated in this review paper. These include: (1) thermal Insulation for different applications (foams, perlites, glass bubbles, aerogel and MLI), (2) sophisticated low-heat-leak support (cryogenic tension straps, trolley bars and posts with dedicated thermal intercepts), and (3) novel cryogenic heat switches.
Multilayer insulation systems that have robust operational characteristics have long been a goal ... more Multilayer insulation systems that have robust operational characteristics have long been a goal of many research projects. Such thermal insulation systems may need to offer some degree of structural support and/or mechanical integrity during loss of vacuum scenarios while continuing to provide insulative value to the vessel. Aerogel-based composite blankets can be the best insulation materials in ambient pressure environments;
IOP Conference Series: Materials Science and Engineering, 2020
Various functional insertion components (FIC), directly connecting a cold mass and the ambient en... more Various functional insertion components (FIC), directly connecting a cold mass and the ambient environment, are irreplaceable and play crucial technical roles in many superconducting cryogenic applications. However, such components also bring a huge heat leak to the cold mass. The heat leak is usually much greater than that through entire evacuated MLI insulation system and solid support structures combined. Therefore, this situation brings unimaginable challenges not only to the refrigeration loads to be met but also critical aspects of the FIC design in satisfaction of highly restrictive, even contradicting technical functions. The FIC must simultaneously minimize the heat leak provide a large amounts of DC current and RF power to/from the cold mass, as well as provide a reliable ultrahigh vacuum thermal isolation break with strong mechanical stability. Reviewed are the following commonly used FICs: 1) various RF input couplers for transmitting MW-RF power; 2) high DC power curren...
IOP Conference Series: Materials Science and Engineering, 2020
High temperature superconducting (HTS) power transmission cables are cooled to operating temperat... more High temperature superconducting (HTS) power transmission cables are cooled to operating temperatures typically below 80 K. A valuable feature of some HTS cables is that they can limit short-circuit fault currents, which can be more than ten times the maximum operating current of a cable. When a fault occurs the HTS wire is no longer superconducting and the heating which occurs will raise the temperature above the allowable operating point. To recover from the fault, the conductor must be cooled down before returning to service. The recovery is affected by the refrigeration system’s performance which varies with load and temperature. A transient numerical model of an HTS cable is applied to investigate the thermal recovery after a fault for some HTS cable system configurations and operating conditions.
ArticleinIEEE Transactions on Applied Superconductivity, 2003
The use of high-temperature superconducting (HTS) materials for power transmission cable applicat... more The use of high-temperature superconducting (HTS) materials for power transmission cable applications is being realized in several utility demonstration projects. Both room-temperature and cold-dielectric cable systems rely on a vacuum cryostat to keep the ambient thermal loads at a minimum. For long-term installations, operating 30 years or longer, the thermal-insulating vacuum pressure may increase in sections of a long length installation. Even if only a small section of the total length of the HTS cable system is affected, localized heating of the cable may reduce the performance of the HTS cable system. A study is presented of the effects of degraded vacuum levels on the operation of HTS cables for different cryogenic thermal insulation systems.
IOP Conference Series: Materials Science and Engineering, 2017
Systematic review is given of development of novel heat switches at cryogenic temperatures that a... more Systematic review is given of development of novel heat switches at cryogenic temperatures that alternatively provide high thermal connection or ideal thermal isolation to the cold mass. These cryogenic heat switches are widely applied in a variety of unique superconducting systems and critical space applications. The following types of heat switch devices are discussed: 1) magnetic levitation suspension, 2) shape memory alloys, 3) differential thermal expansion, 4) helium or hydrogen gap-gap, 5) superconducting, 6) piezoelectric, 7) cryogenic diode, 8) magneto-resistive, and 9) mechanical demountable connections. Advantages and limitations of different cryogenic heat switches are examined along with the outlook for future thermal management solutions in materials and cryogenic designs.
Although some standards exist for thermal insulation, few address the sub-ambient temperature ran... more Although some standards exist for thermal insulation, few address the sub-ambient temperature range and cold-side temperatures below 100 K. Standards for cryogenic insulation systems require cryostat testing and data analysis that will allow the development of the tools needed by design engineers and thermal analysts for the design of practical cryogenic systems. Thus, this critically important information can provide reliable data and methodologies for industrial efficiency and energy conservation. Two Task Groups have been established in the area of cryogenic insulation systems Under ASTM International's Committee C16 on Thermal Insulation. These are WK29609
Flexible, vacuum-insulated transfer lines for low-temperature applications have higher thermal lo... more Flexible, vacuum-insulated transfer lines for low-temperature applications have higher thermal losses than comparable rigid lines. Typical flexible piping construction uses corrugated tubes, inner and outer, with a multilayer insulation (MLI) system in the annular space. Experiments on vacuum insulation systems in a flexible geometry were conducted at the Cryogenics Test Laboratory of NASA Kennedy Space Center. The effects of bending were simulated by causing the inner tube to be eccentric with the outer tube. The effects of spacers were simulated in a controlled way by inserting spacer tubes for the length of the cylindrical test articles. Two material systems, standard MLI and a layered composite insulation (LCI), were tested under the full range of vacuum levels using a liquid nitrogen boiloff calorimeter to determine the apparent thermal conductivity (k-value). The results indicate that the flexible piping under simulated bending conditions significantly degrades the thermal performance of the insulation system. These data are compared to standard MLI for both straight and flexible piping configurations. The definition of an overall k-value for actual field installations (k oa fi) is described for use in design and analysis of cryogenic piping systems.
IOP Conference Series: Materials Science and Engineering, 2015
Standards for thermal insulation used in applications between ambient and low temperatures, below... more Standards for thermal insulation used in applications between ambient and low temperatures, below 100 K, require test data under relevant conditions and by different laboratories to develop data sets for the proper comparisons of materials. This critically important technology is needed to provide reliable data and methodologies for industrial energy efficiency and energy conservation. Under ASTM International's Committee C16 on Thermal Insulation, two standards have been issued on cryogenic thermal insulation systems. Thermal conductivity data sets have been taken using identical flat-plate boiloff calorimeter instruments independently operated at the Cryogenics Test Laboratory of NASA Kennedy Space Center (KSC) and the Thermal Energy Laboratory of LeTourneau University (LETU). Precision specimens of cellular glass insulation were produced for both laboratories to provide the necessary comparisons to validate the thermal measurements and test methodologies. Additional specimens of commercial cellular glass pipe insulation were tested at LETU to compare with the flat plate results. The test data are discussed in relation to the experimental approach, test methods, and manner of reporting the thermal performance data. This initial Inter-Laboratory Study (ILS) of insulation materials for sub-ambient temperature applications provides a foundation for further ILS work to produce standard data sets for several key commercial materials. 1. Introduction There is a need for standard thermal data for cryogenic insulation materials or standard test methods and instrumentation in this area. Standard test methods are needed to produce standard data for conduction of heat by materials in the sub-ambient temperature range. An initial step has been taken for producing standard thermal data through a preliminary Inter-Laboratory Study (ILS) initiated by NASA Kennedy Space Center and LeTourneau University. A major objective of this initial research is to explore the suitability of new methodologies for producing standard data for effective thermal conductivity (ke(T)) and heat flux (q(T)) for commonly used cryogenic insulation materials. Other objectives of this effort are to pave the way for establishing standard data sets for use by engineers, to develop accepted baselines for the performance of novel materials under development, and to provide technical insight on the nature of low heat flows through low-density materials. Knowledge of the dependence of heat transfer related properties on temperature for materials is extremely important because even materials that are considered homogenous may be complicated when applied in systems having temperature differences of several hundred degrees imposed across its thickness.
IOP Conference Series: Materials Science and Engineering
Systematic review is given of development of novel heat switches at cryogenic temperatures that a... more Systematic review is given of development of novel heat switches at cryogenic temperatures that alternatively provide high thermal connection or ideal thermal isolation to the cold mass. These cryogenic heat switches are widely applied in a variety of unique superconducting systems and critical space applications. The following types of heat switch devices are discussed: 1) magnetic levitation suspension, 2) shape memory alloys, 3) differential thermal expansion, 4) helium or hydrogen gap-gap, 5) superconducting, 6) piezoelectric, 7) cryogenic diode, 8) magneto-resistive, and 9) mechanical demountable connections. Advantages and limitations of different cryogenic heat switches are examined along with the outlook for future thermal management solutions in materials and cryogenic designs.
High-temperature superconducting (HTS) cables that typically operate at temperatures below 80 kel... more High-temperature superconducting (HTS) cables that typically operate at temperatures below 80 kelvin (K) are being developed for power transmission. The practical application of HTS power cables will require the use of flexible piping to contain the cable and the liquid nitrogen coolant. A study of thermal performance of multilayer insulation (MLI) was conducted in geometries representing both rigid and flexible piping. This experimental study performed at the Cryogenics Test Laboratory of NASA Kennedy Space Center provides a framework for the development of cost-effective, efficient thermal insulation systems that will support these long-distance flexible lines containing HTS power cables. The overall thermal performance of the insulation system for a rigid configuration and for a flexible configuration, simulating a flexible HTS power cable, was determined by the steady-state liquid nitrogen boiloff method under the full range of vacuum levels. Two different cylindrically rolled material systems were tested: a standard MLI and a layered composite insulation (LCI). Comparisons of ideal MLI, MLI on rigid piping, and MLI between flexible piping are presented.
The Navy intends to use High Temperature Superconducting Degaussing (HTSDG) coil systems on futur... more The Navy intends to use High Temperature Superconducting Degaussing (HTSDG) coil systems on future Navy platforms. The Navy Metalworking Center (NMC) is leading a team that is addressing cryostat configuration and manufacturing issues associated with fabricating long lengths of flexible, vacuum-jacketed cryostats that meet Navy shipboard performance requirements. The project includes provisions to evaluate the reliability performance, as well as proofing of fabrication techniques. Navy cryostat performance specifications include less than 1 Wm-1 heat loss, 2 MPa working pressure, and a 25-year vacuum life. Cryostat multilayer insulation (MLI) systems developed on the project have been validated using a standardized cryogenic test facility and implemented on 5-meterlong test samples. Performance data from these test samples, which were characterized using both LN 2 boiloff and flow-through measurement techniques, will be presented.
IOP Conference Series: Materials Science and Engineering, 2015
The cooling power consumption in large scale superconducting systems is huge and cryogenic device... more The cooling power consumption in large scale superconducting systems is huge and cryogenic devices used in space applications often require an extremely long cryogen holding time. To economically maintain the device at its operating temperature and minimize the refrigeration losses, high performance of thermal isolation is essential. The radiation from warm surrounding surfaces and conducting heat leaks through supports and penetrations are the dominant heat loads to the cold mass under vacuum condition. The advanced developments in various cryogenic applications to successfully reduce the heat loads through radiation and conduction are briefly and systematically discussed and evaluated in this review paper. These include: (1) thermal Insulation for different applications (foams, perlites, glass bubbles, aerogel and MLI), (2) sophisticated low-heat-leak support (cryogenic tension straps, trolley bars and posts with dedicated thermal intercepts), and (3) novel cryogenic heat switches.
Creare has developed a turbo-Brayton cryocooler for the Air Force that is designed to produce app... more Creare has developed a turbo-Brayton cryocooler for the Air Force that is designed to produce approximately 1 kW of refrigeration at 95 K. The cryocooler is intended to provide cryogenic cooling for an air separation system being developed to produce and store liquid oxygen and liquid nitrogen onboard large aircraft. The oxygen will be used for high-altitude breathing and medical evacuation operations, while the nitrogen will be used to inert the ullage space inside the fuel tanks. The cryocooler utilizes gas bearings in the turbomachines for long life without maintenance, which is a critical requirement for this application. The mass of a flight version of this cryocooler is expected to be around 270 kg, while the input power is expected to be 21 to 25 kW. This paper describes the design and testing of the technology demonstration cryocooler that was constructed to establish the feasibility of the approach. In the future, the cryocooler will be integrated and tested with a distillation column subsystem. Subsequent testing may also be performed in-flight on an Air Force transport aircraft.
Although some standards exist for thermal insulation, few address the sub-ambient temperature ran... more Although some standards exist for thermal insulation, few address the sub-ambient temperature range and cold-side temperatures below 100 K. Standards for cryogenic insulation systems require cryostat testing and data analysis that will allow the development of the tools needed by design engineers and thermal analysts for the design of practical cryogenic systems. Thus, this critically important information can provide reliable data and methodologies for industrial efficiency and energy conservation. Two Task Groups have been established in the area of cryogenic insulation systems Under ASTM International's Committee C16 on Thermal Insulation. These are WK29609 -New Standard for Thermal Performance Testing of Cryogenic Insulation Systems and WK29608 -Standard Practice for Multilayer Insulation in Cryogenic Service. The Cryogenics Test Laboratory of NASA Kennedy Space Center and the Thermal Energy Laboratory of LeTourneau University are conducting Inter-Laboratory Study (ILS) of selected insulation materials. Each lab carries out the measurements of thermal properties of these materials using identical flat-plate boil-off calorimeter instruments. Parallel testing will provide the comparisons necessary to validate the measurements and methodologies. Here we discuss test methods, some initial data in relation to the experimental approach, and the manner reporting the thermal performance data. This initial study of insulation materials for sub-ambient temperature applications is aimed at paving the way for further ILS comparative efforts that will produce standard data sets for several commercial materials. Discrepancies found between measurements will be used to improve the testing and data reduction techniques being developed as part of the future ASTM International standards.
... Edited by Susan Breon, Michael Dipirro, David Glaister, John Hull, Peter Kittel, Vitalij Pech... more ... Edited by Susan Breon, Michael Dipirro, David Glaister, John Hull, Peter Kittel, Vitalij Pecharsky, Ray Radebaugh, Jay Theilacker, Steven Van Sciver, John Weisend II, and Albert Zeller. AIP Conference Proceedings, Vol. 613, 2002. Publication Date: 05/2002. Origin: ADS. ...
High-temperature superconducting (HTS) cables that typically operate at temperatures below 80 kel... more High-temperature superconducting (HTS) cables that typically operate at temperatures below 80 kelvin (K) are being developed for power transmission. The practical application of HTS power cables will require the use of flexible piping to contain the cable and the liquid nitrogen coolant. A study of thermal performance of multilayer insulation (MLI) was conducted in geometries representing both rigid and flexible piping. This experimental study performed at the Cryogenics Test Laboratory of NASA Kennedy Space Center provides a framework for the development of cost-effective, efficient thermal insulation systems that will support these long-distance flexible lines containing HTS power cables. The overall thermal performance of the insulation system for a rigid configuration and for a flexible configuration , simulating a flexible HTS power cable, was determined by the steady-state liquid nitrogen boiloff method under the full range of vacuum levels. Two different cylindrically rolled material systems were tested: a standard MLI and a layered composite insulation (LCI). Comparisons of ideal MLI, MLI on rigid piping, and MLI between flexible piping are presented.
Standards for thermal insulation used in applications between ambient and low temperatures, below... more Standards for thermal insulation used in applications between ambient and low temperatures, below 100 K, require test data under relevant conditions and by different laboratories to develop data sets for the proper comparisons of materials. This critically important technology is needed to provide reliable data and methodologies for industrial energy efficiency and energy conservation. Under ASTM International's Committee C16 on Thermal Insulation, two standards have been issued on cryogenic thermal insulation systems. Thermal conductivity data sets have been taken using identical flat-plate boiloff calorimeter instruments independently operated at the Cryogenics Test Laboratory of NASA Kennedy Space Center (KSC) and the Thermal Energy Laboratory of LeTourneau University (LETU). Precision specimens of cellular glass insulation were produced for both laboratories to provide the necessary comparisons to validate the thermal measurements and test methodologies. Additional specimens of commercial cellular glass pipe insulation were tested at LETU to compare with the flat plate results. The test data are discussed in relation to the experimental approach, test methods, and manner of reporting the thermal performance data. This initial Inter-Laboratory Study (ILS) of insulation materials for sub-ambient temperature applications provides a foundation for further ILS work to produce standard data sets for several key commercial materials. 1. Introduction There is a need for standard thermal data for cryogenic insulation materials or standard test methods and instrumentation in this area. Standard test methods are needed to produce standard data for conduction of heat by materials in the sub-ambient temperature range. An initial step has been taken for producing standard thermal data through a preliminary Inter-Laboratory Study (ILS) initiated by NASA Kennedy Space Center and LeTourneau University. A major objective of this initial research is to explore the suitability of new methodologies for producing standard data for effective thermal conductivity (ke(T)) and heat flux (q(T)) for commonly used cryogenic insulation materials. Other objectives of this effort are to pave the way for establishing standard data sets for use by engineers, to develop accepted baselines for the performance of novel materials under development, and to provide technical insight on the nature of low heat flows through low-density materials. Knowledge of the dependence of heat transfer related properties on temperature for materials is extremely important because even materials that are considered homogenous may be complicated when applied in systems having temperature differences of several hundred degrees imposed across its thickness.
The cooling power consumption in large scale superconducting systems is huge and cryogenic device... more The cooling power consumption in large scale superconducting systems is huge and cryogenic devices used in space applications often require an extremely long cryogen holding time. To economically maintain the device at its operating temperature and minimize the refrigeration losses, high performance of thermal isolation is essential. The radiation from warm surrounding surfaces and conducting heat leaks through supports and penetrations are the dominant heat loads to the cold mass under vacuum condition. The advanced developments in various cryogenic applications to successfully reduce the heat loads through radiation and conduction are briefly and systematically discussed and evaluated in this review paper. These include: (1) thermal Insulation for different applications (foams, perlites, glass bubbles, aerogel and MLI), (2) sophisticated low-heat-leak support (cryogenic tension straps, trolley bars and posts with dedicated thermal intercepts), and (3) novel cryogenic heat switches.
Multilayer insulation systems that have robust operational characteristics have long been a goal ... more Multilayer insulation systems that have robust operational characteristics have long been a goal of many research projects. Such thermal insulation systems may need to offer some degree of structural support and/or mechanical integrity during loss of vacuum scenarios while continuing to provide insulative value to the vessel. Aerogel-based composite blankets can be the best insulation materials in ambient pressure environments;
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Papers by Jonathan Demko