Surge analysis of the tank of a gas-insulated line using lumped constant circuits

Surge voltages evaluated by a digital analysis method, for example, electromagnetic transients program (EMTP) and by an analog analysis method (transient network analyzer: TNA) are compared with experimental results on a scaled model of a gas insulated line. From the results, it is confirmed that the analog analysis method has a satisfactory accuracy and its computing speed is quite high. The error caused by the lumped element modeling of the gas insulated line is comparatively small, and the line is not necessary to be treated as a distributed parameter line. The lumped element model is advantageous to understand the mechanism of the transient characteristic of the induced transient voltage. A simple equivalent circuit of the gas insulated line is proposed and its accuracy is confirmed by a comparison with the calculated result obtained by an accurate line method. The transient overvoltages of the tank and across the insulated flange can be analytically calculated using the equivalent model.     

SIZE DISTRIBUTION OF CLUSTERS INHERENT IN RANDOM DISPERSIONS OF EQUAL SPHERES WITH A COAGULATION RADIUS

The spatial structure of a computer-simulated random dispersion of equal spheres is investigated. The sphere of influence, i.e. the coagulation radius, is assumed for each particle without any particle movement. If the distance between sphere centers lies within the coagulation radius, the spheres are regarded as being connected to each other to form a cluster. Various sizes of clusters exist inherently in the random dispersion. The effects of the coagulation radius and the bulk-mean particle volume fraction on the size distribution of clusters are discussed theoretically and experimentally.     

An efficient helium circulation system with small GM cryocoolers

We developed a helium circulating system that re-liquefies all the evaporating helium gas and consumes far less power than conventional systems, because warm helium gas at about 40 K collected high above the surface of the liquid helium in the Dewar is used to keep the Dewar cold, and because cold helium gas just above the liquid helium surface is collected and re-liquefied while still cold. A special transfer tube with multi-concentric pipes was developed to make the system operate efficiently. The system can produce up to 35.5 l/D of liquid helium from the evaporated helium using two 1.5 W@4.2 K GM cryocoolers.     

New radical salts based on TEMPO-substituted 2,4,6-triphenylpyridinium and transition metal complexes

Series of radical salts derived from a 2,4,6-triphenylpyridinium (TPP) carrying TEMPO-substituent and transition metal complexes were prepared by the anion exchange of the TPP–TEMPO tetrafluoroborate with [n-Bu₄N][Ni(dmit)₂], [n-Bu₄N]₂[Pd(dmit)₂], [n-Bu₄N]₂[Pt(dmit)₂], [n-Bu₄N][Ni(mnt)₂], or [n-Bu₄N]₂[Ni(mnt)₂] to give crystals with different structural features. While weak antiferromagnetic interactions of the Curie–Weiss behavior of S = 1/2 spin are predominantly observed in the salts of Pd(dmit)₂, Pt(dmit)₂ and Ni(mnt)₂, the magnetic behavior of 1:1 Ni(dmit)₂ salt can be explained by the additional contribution from the spins on Ni(dmit)₂ anions (χ − χ_TEMPO), obeying the 2D Heisenberg model. A couple of the oxidized salts, [TPP][Ni(dmit)₂] as well as [TPP]₂[Pd(dmit)₂], exhibit semi-conducting properties with relatively high room temperature conductivities.     

日本木作技术书《镰仓造营名目》中的禅宗样斗栱构成与设计方法(其二):与《工程做法则例》的比较研究

本文以 13—19 世纪镰仓建长寺木匠世家河内家族流传下来的建筑技术书籍《镰仓造营名目》为研究对象, 分析了其中记述的禅宗样斗栱的构成与设计方法,继而将其与中国建筑技术书清《工程做法则例》进行了比较研究。 最终确认了中日均有以栱木尺寸为基准单位进行设计的做法,而使用等距控制线以及使用椽子尺寸为基本尺寸单位等做法为日本改进之后的日本化技法。     

日本木作技术书《镰仓造营名目》中的禅宗样斗栱构成与设计方法(其一):与《营造法式》的比较研究

本文以 13—19 世纪镰仓建长寺木匠世家河内家族流传下来的建筑技术书籍《镰仓造营名目》为研究对象, 分析了其中记述的禅宗样斗栱的构成与设计方法,继而将其与中国建筑技术书《营造法式》进行了比较研究。最终确认了中日均有以栱木尺寸为基准单位进行设计的做法, 而使用等距控制线以及使用椽子尺寸为基本尺寸单位等做法为日本改进之后的日本化技法。     

The flow characteristics of an upward gas‐liquid two‐phase flow in a vertical tube with a wire coil: Part 2. Effect on void fraction and liquid film thickness

An experimental study has been carried out to clarify the characteristics of the void fraction and the liquid film thickness of the air‐water two‐phase flow in vertical tubes of 25‐mm inside diameter with wire coils of varying wire diameter and pitch. The flow pattern in the experiment on the average void fraction and the local void fraction distribution in cross section was a bubble flow, and the liquid film thickness was in the region of semiannular and annular flows. It is clarified from these experiments that the average void fraction in tubes with wire coils is lower than that in a smooth tube and decreases with the wire diameter owing to the centrifugal force of the swirl flow which concentrates bubbles at the center of the tube, that the local liquid film thickness becomes more uniform with a decrease in the pitch of the wire coil, and that the liquid film becomes thicker after the passage through the wire coil with an increase in the wire diameter. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(8): 652–664, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10067     

A Study on Characteristics of Cooling Heat Transfer of Supercritical Pressure Fluids in a Plate Heat Exchanger

For the development of industrial heat pump systems supplying a high-temperature heat source over 130°C, experiments were carried out on cooling heat transfer of supercritical pressure fluids flowing in a plate heat exchanger (PHE). Using two refrigerants of HFC134a and HCFC22 as the test fluids, heat transfer coefficient data were obtained at different pressure, flow rate, and heat load conditions. The heat transfer coefficient generally had a maximum in the vicinity of the pseudocritical point and showed seven- to ninefold values compared with tube flow. Based on the measurements, characteristics of cooling heat transfer of supercritical pressure fluids in the PHE were clarified and a correlation of heat transfer coefficient was developed.     

Boiling Heat Transfer and Pressure Drop of a Refrigerant R32 Flowing in a Small Horizontal Tube

In this study, experiments were performed to examine characteristics of flow boiling heat transfer and pressure drop of a low global warming potential refrigerant R32 flowing in a horizontal copper circular tube with 1.0 mm inside diameter for the development of a high-performance heat exchanger using small-diameter tubes or minichannels for air conditioning systems. Axially local heat transfer coefficients were measured in the range of mass fluxes from 30 to 400 kg/(m²·s), qualities from 0.05 to 1.0, and heat fluxes from 2 to 24 kW/m² at the saturation temperature of 10°C. Pressure drops were also measured in the rage of mass fluxes from 30 to 400 kg/(m²·s) and qualities from 0.05 to 0.9 at the saturation temperature of 10°C under adiabatic condition. In addition, two-phase flow patterns were observed through a sight glass fixed at the tube exit with a digital camera. The characteristics of boiling heat transfer and pressure drop were clarified based on the measurements and the comparison with data of R410A obtained previously. Also, measured heat transfer coefficients were compared with two existing correlations.