John Barclay - Academia.edu (original) (raw)

Papers by John Barclay

Test lab-prototype for ~290 K to ~20 K operation of a complete AMRL for LH2 Dec. 31, 2009 GO/NO G... more Test lab-prototype for ~290 K to ~20 K operation of a complete AMRL for LH2 Dec. 31, 2009 GO/NO GO decision for engineering-scale prototype of an AMRL for LH2 December 2010 Test and validate engineering-scale prototype of an AMRL for LH2 Dec. 31, 2010 Complete lab-scale and engineering-scale prototype phases of project

Magnetic refrigeration uses the temperatureand field-dependence of the entropy of some magnetic m... more Magnetic refrigeration uses the temperatureand field-dependence of the entropy of some magnetic materials to accomplish cooling. Because of the intrinsically high efficiency of the magnetization and demagnetization process and because of the potential for excellent heat transfer between solids and fluids, magnetic refrigerators promise to have higher efficiency than existing gascycle refrigerators. Many ground-based and space-based applications could benefit significantly from the cost savings implied by higher efficiency. Other attributes of these devices are high reliability and low volume and mass per unit cooling power. The development of these refrigerators is under way at several places around the world, including the Los Alamos National Laboratory. The progress to date has been encouraging but some problems have been clearly identi fied. The arguments for high efficiency and the problems that will need to be solved to achieve this goal are discussed.

In an effort to develop magnetic regenerators of high efficiency the following geometries were co... more In an effort to develop magnetic regenerators of high efficiency the following geometries were considered: (1) tube channels in solid block; (2) stack of perforated plates normal to the fluid flow direction; (3) stack of solid plates parallel to fluid flow direction, and packed bed of spherical particles; (4) loose packed; and (5) sintered. The overall efficiency of the regenerator, considering heat transfer, longitudinal conduction, and fluid pressure drop, was computed for all the above arrangements as a function of geometrical variables, such as overall length and particle diameter or plate thickness. The results yield the optimum geometry for a given combination of other controlling parameters, such as frequency, porosity, and fluid properties. The different geometries are compared under the constraint that the mass of magnetic material is the same for all. This condition is peculiar to the magnetic refrigeration process because the net refrigeration and driving forces are propo...

Journal of Applied Physics, 2003

The active magnetic regenerator (AMR) uses a magnetic solid as a thermal storage medium and as a ... more The active magnetic regenerator (AMR) uses a magnetic solid as a thermal storage medium and as a working material in a refrigeration cycle. Thermodynamically coupled to a heat transfer fluid, the regenerator produces a cooling effect and generates a temperature gradient across the AMR. The coupling between the heat transfer fluid and the magnetic refrigerant is a key aspect governing the operating characteristics of an AMR. To increase our understanding of AMR thermodynamics, we examine the entropy balance in an idealized active magnetic regenerator. A relation for the entropy generation in an AMR with varying fluid capacity ratios is derived. Subsequently, an expression describing the ideal magnetocaloric effect (MCE) as a function of temperature is developed for the case of zero entropy generation. Finally, the link between ideal MCE and refrigerant symmetry is discussed showing that an ideal reverse Brayton-type magnetic cycle cannot be achieved using materials undergoing a secon...

Cryogenics, 2019

Magnetic refrigeration is a well-known cooling technique based on the magnetocaloric effect (MCE)... more Magnetic refrigeration is a well-known cooling technique based on the magnetocaloric effect (MCE) of certain solids as they enter or leave a high magnetic field. An active magnetic regenerator (AMR) uses certain ferromagnetic materials simultaneously as MCE refrigerants and as a regenerator. An effective active magnetic regenerative refrigeration cycle consists of four steps: adiabatic magnetization with no heat transfer gas flow; heat transfer gas flow at constant high field; demagnetization with no heat transfer gas flow; and heat transfer gas flow at constant low field. The first heat transfer gas flow step from a cold-to-hot temperature in this cycle rejects heat from the magnetized regenerator to a hot sink and the second reverse heat transfer gas flow step from a hot-to-cold temperature absorbs heat from a cold source. Our primary objectives of the present work were to demonstrate an AMR-cycle liquefier, determine the cooling power of a magnetic refrigerant executing an AMR cycle, and understand the impact of intermittent cooling of the AMR cycle of a reciprocating, dual regenerator design with continuous liquefaction and parasitic heat leaks. This article describes how an AMRcycle refrigerator using Gd regenerators moving through ∼2.7 T changes at 0.25 Hz was used to liquefy pure propane at two different supply pressures. The measured rates of liquefaction and elapsed times were measured and used to determine the volume collected and derive cooling power at liquefaction conditions for both runs. These results were compared to those obtained from cool-down temperature vs. time data during the same run. The agreement between the two, independent cooling-power results was excellent after the duty cycle of the AMR cycle cooling was properly treated. No direct measurements of the efficiency were made.

Applied Energy, 2019

Regenerative magnetic cycles are of interest for small-scale, high-efficiency cryogen liquefiers;... more Regenerative magnetic cycles are of interest for small-scale, high-efficiency cryogen liquefiers; however, commercially relevant performance has yet to be demonstrated. To develop improved engineering prototypes, an efficient modeling tool is required to screen the multi-parameter design space. In this work, we describe an active magnetic regenerative refrigerator prototype using a high-field superconducting magnet that produces a 100 K temperature span. Using the experimental data, a semi-analytic AMR element model is validated and enhanced system performance is simulated using liquid propane as a heat transfer fluid. In addition, the regenerator composition and fluid flow are simultaneously optimized using a differential evolution algorithm. Simulation results indicate that a natural gas liquefier with a 160 K temperature span and a second-law efficiency exceeding 20% is achievable.

New Testament Studies, 2012

Mit großer Bestürzung müssen wir den Tod von Professor Dr. Friedrich Avemarie zur Kenntnis nehmen... more Mit großer Bestürzung müssen wir den Tod von Professor Dr. Friedrich Avemarie zur Kenntnis nehmen, der seit Januar  Mitglied unseres Editorial Board war. Professor Avemarie verstarb am .. vollkommen unerwartet an einem Herzinfarkt. Mit seiner Familie trauern seine unmittelbaren Kolleginnen und Kollegen sowie die internationale Gemeinschaft der Neutestamentler und Judaisten. Friedrich Avemarie lehrte seit  Neues Testament, seit  Neues Testament und Antikes Judentum am Fachbereich Evangelische Theologie der Philipps-Universität Marburg. Er stand im Kreis derer, die sich mit der Erforschung des antiken Judentums und des frühen Christentums beschäftigen, in hohem persönlichen und fachlichen Ansehen. Seine Tätigkeit für das NTS-Board war herausragend und hat stark zum Wert der Zeitschrift beigetragen; seine Berichterstattung war stets pünktlich, fair und hilfreich. Wir werden Friedrich Avemarie schmerzlich vermissen. It is with very great sadness that we record the death of Professor Friedrich Avemarie, a serving member of our Editorial Board since January . Professor Avemarie died suddenly of a heart attack on October th , at the age of , leaving his family, his colleagues and the wider world of scholarship shocked and deeply grieved at his loss. Since  Friedrich Avemarie was Professor of New Testament (since , New Testament and Ancient Judaism) in the Fachbereich Evangelische Theologie of the Philipps-Universität Marburg, and he was a highly respected and extremely popular member of the international community of scholars of Ancient Judaism and early Christianity. He was an outstanding member of the NTS Board, whose reports were unfailingly punctual, fair, and helpful, greatly enhancing the value of the Journal. We shall miss him enormously.

Clinica Chimica Acta, 2001

Point-of-care testing POCT can be introduced by laboratory directors or clinicians in response to... more Point-of-care testing POCT can be introduced by laboratory directors or clinicians in response to the need for rapid results to guide treatment. The professional responsibility for ensuring reliable and accurate results is well-defined in some countries such as France, but the role and responsibility of the laboratory is less clear in many other places. When point-of-care instrument technology and the intrinsic design of the device leads to device-specific parameters or analytical differences from laboratory-based equipment, there is a risk of misinterpretation and erroneous treatment decisions. Laboratory staffs are more often aware of the interaction of analytical technology and result interpretation than clinicians, making it more rational to involve the laboratory in the selection of point-of-care equipment, procedures, and therapeutic decisions based on the results. The design control and risk-analysis provisions of emerging regulations such as the EU in Ž. vitro diagnostic medical device IVD can be interpreted as engaging the manufacturer's responsibility, even when the equipment is functioning according to specification. This is especially true of device-specific parameters in which cross-calibration or traceability to a reference material or method is not possible. This is a further argument for involvement of the laboratory in the selection and implementation of point-of-care testing devices.

Analytical Chemistry, 1965

stream flow was 7 cubic meters per second. I t is convenient to clean the silver gauze stirrer be... more stream flow was 7 cubic meters per second. I t is convenient to clean the silver gauze stirrer between experiments with a KCN solution. Stirring of the K C N (3 grams of the salt per 100 ml. of HzO) for 1 or 2 minutes, followed by three 5-minute rinses with water, has always produced a bright, active stirrer which gives reproducible results. Actually, in the experiments described here, 2 pieces of gauze were irradiated simultaneously in the reactor. Their activities are identical and a sample and an "acid blank" can be carried out together. These stirrers show no signs of deterioration after having been used for more than 100 samples or blanks with KCN cleanings between each use.

All papers have been peer-reviewed. The 2007 joint Cryogenic Engineering Conference and Internati... more All papers have been peer-reviewed. The 2007 joint Cryogenic Engineering Conference and International Cryogenic Materials Conference (CEC-ICMC) was held at the Chattanooga Convention Center in Chattanooga, TN, from July 16th through 20th. Nearly 700 attendees from 28 countries came together to enjoy the joint technical programs, industrial exhibit, and special events. There were 382 papers presented in plenary, oral, and poster sessions. Papers in the ICMC part of the conference covered the physical and mechanical properties of metals & alloys at cryogenic temperatures, insulation materials used in magnets for large-scale applications, recent developments in the conventional low-temperature superconductors, YBCO coated conductors, Bi-based superconductors, and MgB2 conductors. Conductor stability & AC losses as well as superconductor applications were also covered at this conference. ICMC papers selected after peer review process are published by AIP as "Conference Proceedings" Volume 986. Readers will get the latest information on materials and their properties used in cryogenic temperatures in this volume.

Chemical Engineering Communications, 1989

Small diameter, gravity-assisted, hydrogen heat pipes were fabricated and tested with performance... more Small diameter, gravity-assisted, hydrogen heat pipes were fabricated and tested with performance limits as a function of tilt angle and working fluid inventory reported. The fabrication method, the filling sequence, and the test procedure are also described. Results are compared with the flooding limit model and operating characteristics of the heat pipe are then discussed. The heat pipe operated over a large fraction of the triple point to critical point domain of the working fluid.

Test lab-prototype for ~290 K to ~20 K operation of a complete AMRL for LH2 Dec. 31, 2009 GO/NO G... more Test lab-prototype for ~290 K to ~20 K operation of a complete AMRL for LH2 Dec. 31, 2009 GO/NO GO decision for engineering-scale prototype of an AMRL for LH2 December 2010 Test and validate engineering-scale prototype of an AMRL for LH2 Dec. 31, 2010 Complete lab-scale and engineering-scale prototype phases of project

Magnetic refrigeration uses the temperatureand field-dependence of the entropy of some magnetic m... more Magnetic refrigeration uses the temperatureand field-dependence of the entropy of some magnetic materials to accomplish cooling. Because of the intrinsically high efficiency of the magnetization and demagnetization process and because of the potential for excellent heat transfer between solids and fluids, magnetic refrigerators promise to have higher efficiency than existing gascycle refrigerators. Many ground-based and space-based applications could benefit significantly from the cost savings implied by higher efficiency. Other attributes of these devices are high reliability and low volume and mass per unit cooling power. The development of these refrigerators is under way at several places around the world, including the Los Alamos National Laboratory. The progress to date has been encouraging but some problems have been clearly identi fied. The arguments for high efficiency and the problems that will need to be solved to achieve this goal are discussed.

In an effort to develop magnetic regenerators of high efficiency the following geometries were co... more In an effort to develop magnetic regenerators of high efficiency the following geometries were considered: (1) tube channels in solid block; (2) stack of perforated plates normal to the fluid flow direction; (3) stack of solid plates parallel to fluid flow direction, and packed bed of spherical particles; (4) loose packed; and (5) sintered. The overall efficiency of the regenerator, considering heat transfer, longitudinal conduction, and fluid pressure drop, was computed for all the above arrangements as a function of geometrical variables, such as overall length and particle diameter or plate thickness. The results yield the optimum geometry for a given combination of other controlling parameters, such as frequency, porosity, and fluid properties. The different geometries are compared under the constraint that the mass of magnetic material is the same for all. This condition is peculiar to the magnetic refrigeration process because the net refrigeration and driving forces are propo...

Journal of Applied Physics, 2003

The active magnetic regenerator (AMR) uses a magnetic solid as a thermal storage medium and as a ... more The active magnetic regenerator (AMR) uses a magnetic solid as a thermal storage medium and as a working material in a refrigeration cycle. Thermodynamically coupled to a heat transfer fluid, the regenerator produces a cooling effect and generates a temperature gradient across the AMR. The coupling between the heat transfer fluid and the magnetic refrigerant is a key aspect governing the operating characteristics of an AMR. To increase our understanding of AMR thermodynamics, we examine the entropy balance in an idealized active magnetic regenerator. A relation for the entropy generation in an AMR with varying fluid capacity ratios is derived. Subsequently, an expression describing the ideal magnetocaloric effect (MCE) as a function of temperature is developed for the case of zero entropy generation. Finally, the link between ideal MCE and refrigerant symmetry is discussed showing that an ideal reverse Brayton-type magnetic cycle cannot be achieved using materials undergoing a secon...

Cryogenics, 2019

Magnetic refrigeration is a well-known cooling technique based on the magnetocaloric effect (MCE)... more Magnetic refrigeration is a well-known cooling technique based on the magnetocaloric effect (MCE) of certain solids as they enter or leave a high magnetic field. An active magnetic regenerator (AMR) uses certain ferromagnetic materials simultaneously as MCE refrigerants and as a regenerator. An effective active magnetic regenerative refrigeration cycle consists of four steps: adiabatic magnetization with no heat transfer gas flow; heat transfer gas flow at constant high field; demagnetization with no heat transfer gas flow; and heat transfer gas flow at constant low field. The first heat transfer gas flow step from a cold-to-hot temperature in this cycle rejects heat from the magnetized regenerator to a hot sink and the second reverse heat transfer gas flow step from a hot-to-cold temperature absorbs heat from a cold source. Our primary objectives of the present work were to demonstrate an AMR-cycle liquefier, determine the cooling power of a magnetic refrigerant executing an AMR cycle, and understand the impact of intermittent cooling of the AMR cycle of a reciprocating, dual regenerator design with continuous liquefaction and parasitic heat leaks. This article describes how an AMRcycle refrigerator using Gd regenerators moving through ∼2.7 T changes at 0.25 Hz was used to liquefy pure propane at two different supply pressures. The measured rates of liquefaction and elapsed times were measured and used to determine the volume collected and derive cooling power at liquefaction conditions for both runs. These results were compared to those obtained from cool-down temperature vs. time data during the same run. The agreement between the two, independent cooling-power results was excellent after the duty cycle of the AMR cycle cooling was properly treated. No direct measurements of the efficiency were made.

Applied Energy, 2019

Regenerative magnetic cycles are of interest for small-scale, high-efficiency cryogen liquefiers;... more Regenerative magnetic cycles are of interest for small-scale, high-efficiency cryogen liquefiers; however, commercially relevant performance has yet to be demonstrated. To develop improved engineering prototypes, an efficient modeling tool is required to screen the multi-parameter design space. In this work, we describe an active magnetic regenerative refrigerator prototype using a high-field superconducting magnet that produces a 100 K temperature span. Using the experimental data, a semi-analytic AMR element model is validated and enhanced system performance is simulated using liquid propane as a heat transfer fluid. In addition, the regenerator composition and fluid flow are simultaneously optimized using a differential evolution algorithm. Simulation results indicate that a natural gas liquefier with a 160 K temperature span and a second-law efficiency exceeding 20% is achievable.

New Testament Studies, 2012

Mit großer Bestürzung müssen wir den Tod von Professor Dr. Friedrich Avemarie zur Kenntnis nehmen... more Mit großer Bestürzung müssen wir den Tod von Professor Dr. Friedrich Avemarie zur Kenntnis nehmen, der seit Januar  Mitglied unseres Editorial Board war. Professor Avemarie verstarb am .. vollkommen unerwartet an einem Herzinfarkt. Mit seiner Familie trauern seine unmittelbaren Kolleginnen und Kollegen sowie die internationale Gemeinschaft der Neutestamentler und Judaisten. Friedrich Avemarie lehrte seit  Neues Testament, seit  Neues Testament und Antikes Judentum am Fachbereich Evangelische Theologie der Philipps-Universität Marburg. Er stand im Kreis derer, die sich mit der Erforschung des antiken Judentums und des frühen Christentums beschäftigen, in hohem persönlichen und fachlichen Ansehen. Seine Tätigkeit für das NTS-Board war herausragend und hat stark zum Wert der Zeitschrift beigetragen; seine Berichterstattung war stets pünktlich, fair und hilfreich. Wir werden Friedrich Avemarie schmerzlich vermissen. It is with very great sadness that we record the death of Professor Friedrich Avemarie, a serving member of our Editorial Board since January . Professor Avemarie died suddenly of a heart attack on October th , at the age of , leaving his family, his colleagues and the wider world of scholarship shocked and deeply grieved at his loss. Since  Friedrich Avemarie was Professor of New Testament (since , New Testament and Ancient Judaism) in the Fachbereich Evangelische Theologie of the Philipps-Universität Marburg, and he was a highly respected and extremely popular member of the international community of scholars of Ancient Judaism and early Christianity. He was an outstanding member of the NTS Board, whose reports were unfailingly punctual, fair, and helpful, greatly enhancing the value of the Journal. We shall miss him enormously.

Clinica Chimica Acta, 2001

Point-of-care testing POCT can be introduced by laboratory directors or clinicians in response to... more Point-of-care testing POCT can be introduced by laboratory directors or clinicians in response to the need for rapid results to guide treatment. The professional responsibility for ensuring reliable and accurate results is well-defined in some countries such as France, but the role and responsibility of the laboratory is less clear in many other places. When point-of-care instrument technology and the intrinsic design of the device leads to device-specific parameters or analytical differences from laboratory-based equipment, there is a risk of misinterpretation and erroneous treatment decisions. Laboratory staffs are more often aware of the interaction of analytical technology and result interpretation than clinicians, making it more rational to involve the laboratory in the selection of point-of-care equipment, procedures, and therapeutic decisions based on the results. The design control and risk-analysis provisions of emerging regulations such as the EU in Ž. vitro diagnostic medical device IVD can be interpreted as engaging the manufacturer's responsibility, even when the equipment is functioning according to specification. This is especially true of device-specific parameters in which cross-calibration or traceability to a reference material or method is not possible. This is a further argument for involvement of the laboratory in the selection and implementation of point-of-care testing devices.

Analytical Chemistry, 1965

stream flow was 7 cubic meters per second. I t is convenient to clean the silver gauze stirrer be... more stream flow was 7 cubic meters per second. I t is convenient to clean the silver gauze stirrer between experiments with a KCN solution. Stirring of the K C N (3 grams of the salt per 100 ml. of HzO) for 1 or 2 minutes, followed by three 5-minute rinses with water, has always produced a bright, active stirrer which gives reproducible results. Actually, in the experiments described here, 2 pieces of gauze were irradiated simultaneously in the reactor. Their activities are identical and a sample and an "acid blank" can be carried out together. These stirrers show no signs of deterioration after having been used for more than 100 samples or blanks with KCN cleanings between each use.

All papers have been peer-reviewed. The 2007 joint Cryogenic Engineering Conference and Internati... more All papers have been peer-reviewed. The 2007 joint Cryogenic Engineering Conference and International Cryogenic Materials Conference (CEC-ICMC) was held at the Chattanooga Convention Center in Chattanooga, TN, from July 16th through 20th. Nearly 700 attendees from 28 countries came together to enjoy the joint technical programs, industrial exhibit, and special events. There were 382 papers presented in plenary, oral, and poster sessions. Papers in the ICMC part of the conference covered the physical and mechanical properties of metals & alloys at cryogenic temperatures, insulation materials used in magnets for large-scale applications, recent developments in the conventional low-temperature superconductors, YBCO coated conductors, Bi-based superconductors, and MgB2 conductors. Conductor stability & AC losses as well as superconductor applications were also covered at this conference. ICMC papers selected after peer review process are published by AIP as "Conference Proceedings" Volume 986. Readers will get the latest information on materials and their properties used in cryogenic temperatures in this volume.

Chemical Engineering Communications, 1989

Small diameter, gravity-assisted, hydrogen heat pipes were fabricated and tested with performance... more Small diameter, gravity-assisted, hydrogen heat pipes were fabricated and tested with performance limits as a function of tilt angle and working fluid inventory reported. The fabrication method, the filling sequence, and the test procedure are also described. Results are compared with the flooding limit model and operating characteristics of the heat pipe are then discussed. The heat pipe operated over a large fraction of the triple point to critical point domain of the working fluid.