Cooldown of Insulated Metal Tubes to Cryogenic Temperatures

Maddox, J. P.; Frederking, T. H. K.

doi:10.1007/978-1-4757-0522-5_57

Cited by 18 publications

(10 citation statements)

References 4 publications

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“…The simplest way to intensify heat transfer is to apply a heat‐insulating layer to the surface of the cooled body . This allows lowering the temperature of the surface in direct contact with the cryogenic liquid, which leads to a reduction in the excess temperature ∆ T .…”

Section: Introductionmentioning

confidence: 99%

Modification of pool boiling regimes by sand deposition

et al. 2019

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Sand spots, attached to a copper ball surface by means of polyvinyl acetate adhesive and distributed over the surface with areal density that ranges between one spot per 1.18 cm 2 (for low-density spots) and one spot per 0.51 cm 2 (for high-density spots), serve as a temporary heat transfer enhancer during the quenching in liquid nitrogen. Highest heat flux densities, achieved during quenching, lie in the range 10.8 to 20.2 W/cm 2 , depending on the sand layer structure.Application of the temporary enhancer increases an amount of heat, evacuated by highly effective nucleate and transition boiling, by factor of 4.5 as compared with the bare sample. The process of sand layer preparation, data acquisition peculiarities, relationship between heat exchange efficiency and the spots areal density, along with sand grit size are discussed in this paper. K E Y W O R D Sheat transfer enhancement, nucleate boiling, temporary enhancer

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Section: Introductionmentioning

confidence: 99%

Modification of pool boiling regimes by sand deposition

et al. 2019

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“…On the other hand, it has been reported that coatings of a poor thermal conductor on metallic components may shorten the lengthy cool-down process of cryogenic equipment [2], [3]. Therefore, we have proposed that cooling fins or coatings of a poor thermal conductor such as PTFE were added on the heater surface, and then it has been reported that cooling fins and coatings of a lower thermal conductor on the heated surface improved the recovery time [4], [5].…”

Section: Introductionmentioning

confidence: 99%

Improvement of Recovery Characteristics of REBCO Tape With Several Surface Conditions for Resistive Fault Current Limiter

Tamashima

Takaya

Shirai

et al. 2017

IEEE Trans. Appl. Supercond.

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Abstract-Superconducting Fault Current Limiters (SFCLs) are required to return to the superconducting state within the proper time (recovery time) after limiting a fault current according to a relay operation scheme in a power system. In order to apply SFCLs to power systems, the recovery time is important property and deeply depends on the heat transfer property of the heated surface of the superconducting tape (normal conducting state) to liquid nitrogen.It has been confirmed that REBCO tapes with various shaped fins or PTFE coating improved cooling property. In this paper, to clear the mechanism of cooling property improvement of fins or PTFE coating, boiling phenomena on REBCO tapes with some types of fins or PTFE coating was observed by use of high speed video camera. The influence on the cooling improvement property of cooling fins and PTFE coating was discussed according to the photographical view of the boiling phenomenon. 

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“…It was reported coatings of a poor thermal conductor on metallic components may shorten the lengthy cool-down process of cryogenic equipment [3], [4]. PTFE coating is also expected to promote the nucleate boiling and to make vapor film unstable.…”

Section: Introductionmentioning

confidence: 99%

Recovery Characteristics of GdBCO Superconducting Tape With Cooling Fins and Teflon Coating for Resistive Fault Current Limiter

Shirai

Yoneda

Higa

et al. 2016

IEEE Trans. Appl. Supercond.

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Abstract-Recovery time defined as the time during which the superconducting component recovers to its initial condition after the current limiting operation, is very important to design an SFCL. In this paper, the cooling properties of GdBCO superconducting tape with various types of fins or PTFE (polytetrafluoroethylene:Teflon) coating were investigated. Superconducting tape was heated by current, which was larger than its critical current, in liquid nitrogen. The cooling down speed after the current shut down from film boiling to nonboiling and to the superconducting state was investigated. To clarify the effect of surface condition on the heat transfer characteristics, the superconducting test tapes with various shaped fins or PTFE coating were compared with that without fins/coating. According to the experimental results, it was confirmed that superconducting tape with fins or PTFE coating recovered to the superconducting state faster than that without fins/coating and is hopeful for the cooling design of SFCL.

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Cooldown of Insulated Metal Tubes to Cryogenic Temperatures

Cited by 18 publications

References 4 publications

Modification of pool boiling regimes by sand deposition

Modification of pool boiling regimes by sand deposition

Improvement of Recovery Characteristics of REBCO Tape With Several Surface Conditions for Resistive Fault Current Limiter

Recovery Characteristics of GdBCO Superconducting Tape With Cooling Fins and Teflon Coating for Resistive Fault Current Limiter

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