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At least 109 records · Page 6

All sources NASA NTRS DOE OSTI

NASA NTRS1984

Magnetically suspended Stirling cryogenic space refrigerator Test results

In 1979, a project leading to the development of a Stirling type cryogenic refrigerator for spaceborne application was initiated. The refrigerator is to generate five watts of net cooling at a temperature of 65 K. An operation without maintenance for a period of five years is required. A novel approach was selected for meeting the life requirement, taking into account an electromagnetic suspension of the moving parts. The fabrication of the hardware has now been completed and the performance of the refrigerator has been measured. The present paper provides a short review of the Stirling cycle, a description of the refrigerator design, and a summary of the test results. The new refrigerator configuration contains four major features, including a purely rectilinear drive, magnetic bearings, clearance seals, and all metal/ceramic working space surfaces. The displacer and the piston are supported and guided by magnetic bearings. The magnetic bearing consists of a set of electromagnetic actuators and radial position transducers.

Daniels, A.↗

NASA NTRS1985

Reciprocating magnetic refrigerator

A 4 to 15 K magnetic refrigerator to test as an alternative to the Joule-Thomson circuit as the low temperature stage of a 4 to 300 K closed-cycle refrigerator was developed. The reciprocating magnetic refrigerator consists of two matrices of gadolinium gallium garnet spheres located in tandem on a single piston which alternately moves each matrix into a 7 telsa magnetic field. A separate helium gas circuit is used as the heat exchange mechanism for the low and the high temperature extremes of the magnetic refrigerator. Details of the design and results of the initial refrigerator component tests are presented.

Johnson, D. L.↗

NASA NTRS1985

Effects of leakage through clearance seals on the performance of a 10 K Stirling-cycle refrigerator

The use of clearance seals is essential to achieve long life, wear free operation of Stirling cycle cryogenic refrigerators. The effect of leakage through clearance seals on the performance of such a refrigerator operating at temperatures ranging from 20 K down to 10 K was determined. The ability of a Stirling cycle refrigerator to achieve 10 K with clearance seals was successfully demonstrated. It is indicated that the leakage flow undergoes gap regeneration before reaching the cold expansion volume. A simple model of gap regeneration was used to estimate the regeneration loss due to the leakage flow. This regeneration process minimizes the loss in refrigerator performance caused by the clearance seal leakage. It is found that clearance seals remain effective down to a refrigeration temperature of 10 K.

Keung, C. S.↗

NASA NTRS1986

The 1- to 4-K refrigeration techniques for cooling masers on a beam waveguide antenna

The status of technology is reported for various 1- to 4-K commercially available refrigeration systems capable of producing 1.5-K refrigeration to cool masers and superconducting cavity oscillators on the proposed beam waveguide antenna. The design requirements for the refrigeration system and the cryostat are presented. A continuously operating evaporation refrigerator that uses capillary tubing to provide a continuous, self-regulating flow of helium at approximately 1.5 K has been selected as the first refrigerator design for the beam waveguide antenna.

Johnson, D. L.↗

NASA NTRS1987

Sorption compressor/mechanical expander hybrid refrigeration

Experience with Deep Space Network (DSN) ground-based cryogenic refrigerators has proved the reliability of the basic two-stage Gifford-McMahon helium refrigerator. A very long life cryogenic refrigeration system appears possible by combining this expansion system or a turbo expansion system with a hydride sorption compressor in place of the usual motor driven piston compressor. To test the feasibility of this system, a commercial Gifford-McMahon refrigerator was tested using hydrogen gas as the working fluid. Although no attempt was made to optimize the system for hydrogen operation, the refrigerator developed 1.3 W at 30 K and 6.6 W at 60 K. The results of the test and of theoretical performances of the hybrid compressor coupled to these expansion systems are presented.

Jones, J. A.↗

NASA NTRS1987

Oxygen chemisorption compressor study for cryogenic J-T refrigeration

Over twenty potentially reversible heat-powered oxide reactions have been studied and/or tested to determine their potential use as thermochemical oxygen compressors for cryogenic J-T LO2 refrigerators. One gas-solid compound family, Pr(1-n)Ce(n)O(x), proved to be completely reversible with fast kinetics for all pressure ranges tested below 650 C. With a heat-powered charcoal/methane physical adsorption upper stage and a Pr(1-n)Ce(n)O(x) chemisorption lower stage, temperatures should be attainable in the 55-80 K range for less power and over five times less weight than for charcoal/nitrogen sorption refrigeration systems. Total system power requirements with a hydride chemisorption lower stage (10 K to 7 K minimum) are about three times less than any mechanical refrigerator, and spacecraft refrigeration weights are about twenty times less. Due to the lack of wear-related moving parts in sorption refrigerators, life expectancy is at least ten years, and there essentially no vibration.

Jones, Jack A.↗

NASA NTRS1988

Laboratory testing of a supercritical helium pump for a magnetic refrigerator

A supercritical helium testing system for a magnetic refrigerator has been built. Details of the supercritical helium pump, the test system, and the test instrumentation are given. Actual pump tests were not run during this ASEE term because of delivery problems associated with the required pump flow meter. Consequently, efforts were directed on preliminary design of the magnetic refrigeration system for the pump. The first concern with the magnetic refrigerator design was determining how to effectively make use of the pump. A method to incorporate the supercritical helium pump into a magnetic refrigerator was determined by using a computer model. An illustrated example of this procedure is given to provide a tool for sizing the magnetic refrigerator system as a function of the pump size. The function of the computer model and its operation are also outlined and discussed.

Wang, Pao-Lien↗

NASA NTRS1990

Dilution refrigeration for space applications

Dilution refrigerators are presently used routinely in ground based applications where temperatures below 0.3 K are required. The operation of a conventional dilution refrigerator depends critically on the presence of gravity. To operate a dilution refrigerator in space many technical difficulties must be overcome. Some of the anticipated difficulties are identified in this paper and possible solutions are described. A single cycle refrigerator is described conceptually that uses forces other than gravity to function and the stringent constraints imposed on the design by requiring the refrigerator to function on the earth without using gravity are elaborated upon.

Israelsson, U. E.↗

NASA NTRS1990

Magnetic refrigeration using flux compression in superconductors

The feasibility of using flux compression in high-temperature superconductors to produce the large time-varying magnetic fields required in a field cycled magnetic refrigerator operating between 20 K and 4 K is presently investigated. This paper describes the refrigerator concept and lists limitations and advantages in comparison with conventional refrigeration techniques. The maximum fields obtainable by flux compression in high-temperature supercoductor materials, as presently prepared, are too low to serve in such a refrigerator. However, reports exist of critical current values that are near usable levels for flux pumps in refrigerator applications.

Israelsson, U. E.↗

NASA NTRS1990

A rocket-borne He-3 refrigerator

A self-contained, recyclable He-3 refrigerator suitable for use in space has been developed. The refrigerator is compact, has no moving parts, and requires only electrical connections and thermal contact in order to operate from a 2 K cold stage. A charcoal adsorption pump is used to efficiently condense and cool the He-3. Sintered copper confines the He-3 to the evaporator in zero-gravity and, in fact, allows the refrigerator to operate upside-down in the laboratory. Mounted on a 2 K cold stage, the refrigerator provides 100 microwatts of cooling power at 346 mK, with a 7 hour hold time. On a 1.5 K cold stage, the lowest temperature achieved is 277 mK. The refrigerator has been vibration tested at 7.5 G amplitude from 30 to 400 Hz and 15 G amplitude from 400 to 2000 Hz.

Duband, L.↗

NASA NTRS1996

Thermoelectric refrigerator

A refrigerator is provided which combines the benefits of superinsulation materials with thermoelectric devices and phase change materials to provide an environmentally benign system that is energy efficient and can maintain relatively uniform temperatures for extended periods of time with relatively low electrical power requirements. The refrigerator includes a thermoelectric assembly having a thermoelectric device with a hot sink and a cold sink. The superinsulation materials include a plurality of vacuum panels. The refrigerator is formed from an enclosed structure having a door. The vacuum panels may be contained within the walls of the enclosed structure and the door. By mounting the thermoelectric assembly on the door, the manufacturer of the enclosed structure is simplified and the overall R rating of the refrigerator increased. Also an electrical motor and propellers may be mounted on the door to assist in the circulation of air to improve the efficiency of the cold sink and the hot sink. A propeller and/or impeller is preferably mounted within the refrigerator to assist in establishing the desired air circulation flow path.

Park, Brian V.↗

NASA NTRS2013

20 K Helium Refrigeration System for NASA-JSC Chamber-A

A new 20 K helium refrigerator installed at NASA Johnson Space Center's Space Environment Simulation Laboratory (SESL) was successfully commissioned and tested in 2012. The refrigerator is used to create a deep space environment within SESL s Chamber A to perform ground testing of the James Webb Space Telescope. The chamber previously and currently still has helium cryopumping panels (CPP) and LN2 shrouds used to create Low Earth Orbit environments. Now with the new refrigerator and new helium shrouds (45 x 65 ) the chamber can create a deep space environment. The process design, system analysis, specification development, and commissioning oversight were performed by the cryogenics department at Jefferson Labs, while the contracts and system installation was performed by the ESC group at JSC. Commissioning data indicate a inverse coefficient of performance better than 70 W/W for a 18 KW load at 20 K (accounting for liquid nitrogen precooling power) that remains essentially constant down to 1/3 of this load. Even at 10 percent of the maximum capacity, the performance is better than 140 W/W at 20K. The refrigerator exceeded all design goals and demonstrated the ability to support a wide load range from 10kW at 15 K to 100 kW at 100K. The refrigerator is capable of operating at any load temperature from 15K to ambient with tight temperature stability. The new shroud (36 tons of aluminum) can be cooled from room temperature to 20 K in 24 hours. This paper will outline the process design and commissioning results.

Homan, J.↗

NASA NTRS2013

Commissioning of a 20 K Helium Refrigeration System for NASA-JSC Chamber A

A new 20 K helium refrigerator installed at NASA Johnson Space Center s Space Environment Simulation Laboratory (SESL) was successfully commissioned and tested in 2012. The refrigerator is used to create a deep space environment within SESL s Chamber A to perform ground testing of the James Webb Space Telescope (JWST). The chamber previously and currently still has helium cryo-pumping panels (CPP) and liquid nitrogen shrouds used to create low earth orbit environments. Now with the new refrigerator and new helium shrouds the chamber can create a deep space environment. The process design, system analysis, specification development, and commissioning oversight were performed by the cryogenics department at Jefferson Lab, while the contracts and system installation was performed by the ESC group at JSC. Commissioning data indicate an inverse coefficient of performance better than 70 W/W for a 18 kW load at 20 K (accounting for liquid nitrogen pre-cooling power) that remains essentially constant down to one third of this load. Even at 10 percent of the maximum capacity, the performance is better than 150 W/W at 20 K. The refrigerator exceeded all design goals and demonstrated the ability to support a wide load range from 10 kW at 15 K to 100 kW at 100 K. The refrigerator is capable of operating at any load temperature from 15 K to ambient with tight temperature stability. The new shroud (36 tons of aluminum) can be cooled from room temperature to 20 K in 24 hours. This paper will outline the process design and commissioning results.

Homan, J.↗

DOE OSTI2024

Evaluation of Leak Detection Technologies for Low Global Warming Potential (GWP), Flammable Refrigerants

Current commercial refrigeration systems use refrigerants with global warming potential (GWP) values ranging from 1250 to 4000. The emergence of low GWP alternatives (GWP <150) is expected to significantly reduce direct emissions in this sector, playing a crucial role in the ongoing electrification and decarbonization initiatives. However, many of these low GWP alternatives pose a flammability risk, necessitating robust sensing solutions to ensure the reliable and safe operation of the equipment. This paper examines various sensing mechanisms suitable for potential applications in systems that employ flammable refrigerants, specifically those designated as A2L class. It provides a summary of A2L refrigerants and their properties, followed by a comprehensive review of sensor classes, covering their working principles, features, advantages, and limitations. Additionally, the article delves into key performance characteristics such as accuracy, selectivity, sensitivity, dynamic characteristics, and durability, among other properties. The article discusses areas for improvement and suggests corresponding approaches for potential sensors in facilitating the successful adoption of flammable refrigerants. Finally, this paper presents the latest findings from experimental evaluation of 5 different sensing principles in detecting the composition variation as a result of various operational conditions. Reliability and sensitivity of the sensor in responding to shifts in true composition and the resultant LFL value is also discussed.

Reshniak, Viktor↗

DOE OSTI2025

Optimizing flow condensation models for next-generation refrigerants in axial micro-fin aluminum tubes

To support the transition to next-generation refrigerants, accurate modelling of heat transfer and pressure drop is essential for designing efficient heat exchangers. Current models, largely based on traditional refrigerants and unexpanded micro-fin tubes, may not reliably predict performance for new refrigerants and expanded micro-fin geometries. This study evaluates four condensation models using experimental data for six A2L refrigerants: R-32, R-454B, R-454C, R-455A, R-1234yf, and R-1234ze(E). For heat transfer models, the Han and Lee (2005) model initially yields the best accuracy (mean absolute Deviation, MAD = 22.1%). To further improve predictions, a correction factor reduces the Cavallini et al. (2009) model’s MAD from 68.2% to 15.4%, while optimization of the Kedzierski and Goncalves (1997) model achieves a MAD of 13.1%. For pressure drop, the Cavallini et al. (1997) model proves most accurate (MAD = 6.4%), with the simpler Haraguchi et al. (1993) model also effective (MAD = 9.4%). Keywords: Flow condensation models, heat transfer coefficient, frictional pressure drop, next-generation refrigerants, aluminum micro-fin tubes

Hu, Yifeng [ORNL] (ORCID:0000000242875185)↗

DOE OSTI2026

Modeling and Energy Analysis of Refrigeration Systems in Supermarkets: A Case Study

Refrigeration systems are the single largest consumer of electricity in supermarkets, accounting for approximately 40–60% of total store electricity use. As supermarkets face increasing pressures to improve efficiency and reduce operational costs, understanding the energy performance of refrigeration systems in supermarkets has become essential. In this paper, we investigate the energy performance and patterns of the refrigeration system using field measurements in one supermarket. The compressor coefficient of performance (COP) averaged 4.5 during nighttime steady-state operation, providing a practical efficiency benchmark. We develop simple physical-based load models for the display cases in the supermarket, where the refrigeration system uses R404A. The results show the display case models achieve a good agreement with measured data, validating its utility for energy estimation during unoccupied hours. Finally, the analysis reveals several challenges of data collection systems for refrigeration systems in the supermarket industry as well.

Chen, Yimin [ORNL] (ORCID:0000000338181655)↗

DOE OSTI2022

Grey-box Fault Models and Applications for Low Carbon Emission CO2 Refrigeration System

CO2 refrigeration systems have attracted more attentions in recent years because of their zero-carbon emission advantages compared with traditional refrigerants. These systems are widely used in certain commercial buildings such as supermarkets. However, very limited energy studies have been done for such refrigeration systems under faults. Furthermore, this study investigated five common faults for supermarket transcritical CO2 refrigeration systems with display cases. The following major tasks were implemented for this study. (1) Five fault models (gray-box format) regarding the power consumption and supply air temperature were proposed for low- and high-temperature display cases, respectively. The models cover: ice accumulation on evaporator coil, evaporator fan partial failure, expansion valve failure, display door open, and condenser blockage. (2) These fault models were calibrated with field tests, and the modeling accuracies were in good agreement with measurement datasets. (3) The proposed fault models demonstrated more than 90% of fault detection for Fault Detection and Diagnostics (FDD) purposes for both field measurement and simulated data.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

NASA NTRS2014

Salt Pill Design and Fabrication for Adiabatic Demagnetization Refrigerators

The performance of an adiabatic demagnetization refrigerator (ADR) is critically dependent on the design and construction of the salt pills that produce cooling. In most cases, the primary goal is to obtain the largest cooling capacity at the low temperature end of the operating range. The realizable cooling capacity depends on a number of factors, including refrigerant mass, and how efficiently it absorbs heat from the various instrument loads. The design and optimization of "salt pills" for ADR systems depend not only on the mechanical, chemical and thermal properties of the refrigerant, but also on the range of heat fluxes that the salt pill must accommodate. Despite the fairly wide variety of refrigerants available, those used at very low temperature tend to be hydrated salts that require a dedicated thermal bus and must be hermetically sealed, while those used at higher temperature - greater than about 0.5 K - tend to be single-‐ or poly-‐crystals that have much simpler requirements for thermal and mechanical packaging. This paper presents a summary of strategies and techniques for designing, optimizing and fabricating salt pills for both low-‐ and mid-‐temperature applications.

sub-kelvin cooling↗