低温工学
Online ISSN : 1880-0408
Print ISSN : 0389-2441
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28 巻 , 2 号
選択された号の論文の8件中1~8を表示しています
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  • 荻野 治
    28 巻 (1993) 2 号 p. 65
    公開日: 2010/02/26
    ジャーナル フリー
  • 児玉 隆夫
    28 巻 (1993) 2 号 p. 66-73
    公開日: 2010/02/26
    ジャーナル フリー
    Following an introduction of basic principles of a dilution refrigeration and a few comments on the nuclear demagnetization to produce ultra-low temperatures, a couple of methods to measure its temperature are described. As a typical example of quantum phenomena at ultra-low temperatures, some characteristic features of the superfluid 3He, nuclear ordered solid 3He, some properties of 3He-4He dilute solutions and enhanced nuclear magnetism are briefly described.
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  • 西嶋 茂宏
    28 巻 (1993) 2 号 p. 74
    公開日: 2010/02/26
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  • 佐藤 明男
    28 巻 (1993) 2 号 p. 75-85
    公開日: 2010/02/26
    ジャーナル フリー
    In every stage of experiment in low temperature physics and cryogenic engineering liquid helium and nitrogen are used popularly, but they are not necessarily used properly. The proper usage of these cryogen is reconsidered in this article by investigating the thermophysical property differences in latent heat, thermal conductivity, enthalpy and so on. To make your own cryogenic “map” based on thermophysical properties compared with other cryogen as hydrogen and oxygen would be the key to solve troubles encountered in your experiment.
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  • 山田 豊, 長谷部 次教, 柳谷 知之, 直原 和哲, 石塚 正之, 安原 征治, 石原 守
    28 巻 (1993) 2 号 p. 86-91
    公開日: 2010/02/26
    ジャーナル フリー
    Superconducting properties of Bi-Pb-Sr-Ca-Cu-O superconducting bulk fabricated by intermediate cold isostatic pressing (C. I. P.) process have been investigated, and heat leakage per a bulk lead pair from 77K to 4.2K has been evaluated. The critical current density of the tubular bulk, approximately inner diameter 10-30mm and 200mm long, was indicated more than 1, 000A/cm2 at 77K under self-magnetic field, and at 4.2K was indicated as about 2, 000A/cm2 under 15T. The reasons for improvement of Jc are the formation of high Tc single phase and highly aligned microstructure of the bulk. The heat leakage per a pair of the bulk leads from 77K to 4.2K has been measured to be 0.16W at DC 800A and considered to be less than one-tenth of that of 800A-class conventional gas-cooled current leads.
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  • 村上 正秀, 羽生 哲也, 瀬尾 和哉
    28 巻 (1993) 2 号 p. 92-98
    公開日: 2010/02/26
    ジャーナル フリー
    The thermomechanical flow of He II through a porous element for a fountain effect pump was experimentally investigated to understand the general flow characteristics and to develop an evaluation formula for the flow rate. Two types of elements, compressed alumina powder elements and SUS fiber elements, were tested in a systematic way. The two flow states, the ideal and superfluid turbulent states, are found to exist according to the magnitude of heat input. It is a general conclusion that the flow rate through the former elements is always far smaller than the prediction from the straight forward application of the Corter-Mellink formula in the superfluid turbulent state. In order to resolve the inconsistency, the effective flow passage model is proposed, in which the tortuosity is introduced to take account of the winding of micro flow pas sages in an element. The model leads to firm understanding of general flow characteristics in both qualitative and quantitative senses, and to deriving the dynaical similarity law for the mass flow rate and the theoretical maximum flow rate. However, the tortuosity experimentally obtained with the alumina elements was considered to be too large, that is to say 4 to 5. On the other hand, those of SUS elements are found to be one or nearly one as expected from the interior structure. It is concluded that the flow rate degradation in the superfluid turbulent state is resulted mostly from the winding effect of passages, and that the model is confirmed to be quite valid.
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  • 富永 昭
    28 巻 (1993) 2 号 p. 99-107
    公開日: 2010/02/26
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    Discusssed are dissipation of kinetic energy due to viscosity and radial distributions of velocity and entropy. The viscous dissipation Wν and the function fν related to the radial distribution of velocity are discussed using a linearized form of the Euler equation with a long-wave approximation The radial distribution of entropy fα is discussed using linearized form of the general equation of heat transport with a long-wave approximation. These distribution functions depend on geometry of the flow channel. Analytic solutions are obtained for a parallel plane case and a circular cylinder case. Corresponding to the thermal diffusivity α and the kinematic viscosity ν, two characteristic times ταr02/2α and τνr02/2ν are introduced, ωτα=0 corresponds to the quasistatic limit, and for finite ωτα the distribution of entropy is inhomogeneous because of the irreversible process due to thermal diffusion. For large ωτν the distribution of velocity is homogeneous except for near the solid wall, and for small ωτν the distribution of velocity is parabolic, similarly to the case of stationary flow. After discussions on χν≡‹fνr and χα≡‹fαr, the function g≡‹fα(1-fν+)/(1-χν+)›r is discussed. Main results are followings: using Yλ≡(1+i)(ωτλ)1/2(λ=α and ν), fλ=cosh(Yλr/r0)/cosh(Yλ) and χλ≡‹fλr=tanh(Yλ)/Yλ for a parallel plane case having separation of 2r0, and fλ={J0(iYλr/r0)}/{J0(iYλ)} and χλ≡‹fλr={2J1(iYλ)}/{iYνJ0(iYλ)} for a circular cylinder case having diameter of 2r0. For both cases g=(χαν+)/{(1+σ)(1-χν+)} where σ≡ν/α is the Prandtl number.
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  • 富永 昭
    28 巻 (1993) 2 号 p. 108-113
    公開日: 2010/02/26
    ジャーナル フリー
    Discussed are axial variations of five variables ‹p·pt, AI≡‹p·Aurt, ‹p·A‹ξ›rt, ‹‹ur·‹urt and ‹‹ξ›r·‹ξ›rt required for calculating the heat flow AQ and the work source AW per unit length. Discussions are based on linearized forms of the continuity equation and the Euler one. The continuity equation leads to the first relationship ∇_??_(AI)=AW where A is cross-sectional area of the flow channel. The Euler equation leads to the second relationship ∇‹p·pt={(2ωρm)/(|1-χν|2)}·[{(1-χν′)ω‹p·A‹ξ›rtνAI}/A] and the third relationship ∇_??_ψ={(ωρm)/(|1-χν|2)}·[{χν″ω‹p·A‹ξ›rt-(1-χν′)AI}/A‹p·p›t] where ψ is phase of pressure oscillation. A couple of the continuity equation and the Euler one leads to the fourth relationship ∇_??_‹p·A‹ξ›rt=(β∇_??_Tm)FSα′‹p·A‹ξ›rt+(χα″/ω)AI]-[KS+(KT-KS)FSχα′]Ap·pt+{(1-χν′)/(|1-χν|2)}Aρm‹‹ur·‹urt. These equations are supplemented by the following two relationships ‹‹ur·‹urt2‹‹ξ›r·‹ξ›rt. ‹‹ξ›r·‹ξ›rt={(‹p·A‹ξ›rt)2}/(A2p·pt)+{(AI)2}/{(Aω)2p·pt}. The first, the second and the forth relationships are, therefore, three differential equations between three independent variables ‹p·pt, ‹p·A‹ξ›rt and AI. A wave equation is derived also from the continuity equation and the Euler one. It is used to show that the stability limit is the same as that derived by N. Rott in the case that the temperature distribution is described by a step function.
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