Advances in cryogenic engineering 

About: Advances in cryogenic engineering is an academic journal. The journal publishes majorly in the area(s): Cryogenics & Superconducting magnet. It has an ISSN identifier of 0065-2482. Over the lifetime, 2435 publications have been published receiving 13591 citations.

Description and Performance of a Near-Room Temperature Magnetic Refrigerator

Abstract: Magnetic refrigeration has been viewed as primarily a cryogenic technology because the necessary high magnetic fields are most easily provided by superconducting magnets. However, some of the largest magnetocaloric effects are exhibited by gadolinium-based alloys near room temperature. Ames Laboratory and Astronautics Corporation of America have been collaborating to apply such materials to large-scale commercial and industrial cooling near room temperature. Astronautics has designed and operated a reciprocating magnetic refrigerator that uses water as a heat transfer fluid. The device uses the active magnetic regeneration concept of recent cryogenic devices, but in contrast to the cryogenic case, the heat capacity of the fluid in the pores of the regenerator bed is comparable to that of the solid matrix. Using a 5 T field, the refrigerator reliably produces cooling powers exceeding 500 watts at coefficients of performance of 6 or more. This record performance puts magnetic refrigeration in a class with the best of current technology, vapor cycle refrigeration, without having to use volatile, environmentally hazardous fluids.

A Comparison of Three Types of Pulse Tube Refrigerators: New Methods for Reaching 60K

Abstract: Pulse tube or thermoacoustic refrigerators require only one moving part—an oscillating piston or diaphragm at room temperature. Refrigeration occurs within a tube connected to the pressure wave generator when the thermal relaxation time between gas and tube is comparable to a half period. Three types have been discussed in the literature recently by Gifford, by Mikulin, and by Wheatley. A record low temperature of 60 K was achieved in our work using a single stage pulse tube similar to that of Mikulin. Previously 105 K was the lowest temperature achieved. Because of only one moving part, all three types have the potential for long life, but their efficiency and intrinsic limitations have never been investigated. This paper compares the three types with each other and with common refrigerators such as Joule-Thomson and Stirling refrigerators. An apparatus is described which can measure the intrinsic behavior of the different types from temperatures of about 30 K to 300 K. Overall cycle efficiency as well as sources of loss such as conduction and regenerator ineffectiveness are discussed and the advantages of various phase shifting techniques to increase refrigeration capacity are compared.

Nb3Al Multifilamentary Wires Continuously Fabricated by Rapid-Quenching

Abstract: The Nb tube process has recently been developed at NRIM(Japan) for fabricating Nb3Al multifilamentary superconductors,1–3 which are characterized by the heat treatment at low temperature ( 1700°C), many attempts were made to form Nb3A1 by heat treating Nb/AI composite at high temperatures.4–6 However, rapid grain growth decreased the density of pinning center (grain boundary) in Nb3A1 and thereby degraded Jc in particular at low magnetic fields. To overcome this problem, Nb3A1 conductors fabricated through a rapid-quenching process have been studied. In this process the A15 Nb3A1 phase with fine grain structure can be precipitated from the supersaturated Nb-Al bcc phase by aging at ~800°C. However, no attempt was made to fabricate a practical-structure conductor such as a long multifilamentary wire through continuous rapid-quenching and subsequent annealing (post annealing) process.

Performance Deterioration in High Effectiveness Heat Exchangers Due to Axial Heat Conduction Effects

Abstract: The design of high-effectiveness heat exchangers for cryogenic applications requires consideration of axial heat conduction in flow direction, through exchanger core and fluids, an effect which generally can be neglected in conventional heat exchanger work. The most severe performance deterioration is encountered when both fluids have the same heat capacity rate. As indicated schematically in Fig. 1, the temperature difference between fluids which is already small throughout the exchanger is further decreased by axial conduction effects.

Nb3Sn Conductor Development for Fusion and Particle Accelerator Applications

Abstract: Oxford Instruments, Superconducting Technology (OST) produces high performance Nb3Sn wire via several different “internal tin” routes OST now routinely produces long lengths of strand made by the Restacked Rod Process that achieve 12 T, 42 K non‐Cu critical current density (Jc) values of 3000 A/mm2 with good RRR values We are now investigating the effect of Ta and Ti doping on high field (25 T) properties, as well as reducing the effective filament diameter of this strand design by increasing the number of elements of the restack from 61 up to 127 and beyond OST is also involved with research for the US‐HEP National Conductor Program Results on distributed barrier internal tin composites made entirely by hot extrusion with self‐separating Nb‐Ti dividers will be presented This process is being developed for the production scale‐up of internal tin Nb3Sn strand Finally, the results of our latest round of composites having lower ac losses for fusion applications (ITER) will be presented