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The premixed flame propagation with conductive heat loss in millimeter-scale narrow closed cells of different gap widths is investigated experimentally and numerically. The flame evolution is obser...

In the present work, artificial roughness in the form V-ribs with symmetrical gaps have been applied on the heated surface to enhance the heat transfer in the limbs of V-ribs. Symmetrical gaps on both legs were provided by varying the relative gap width from 1 to 5 and number of gaps from 1 to 5. The relative roughness pitch, relative roughness height and aspect ratio of the rectangular duct are kept constant to the value of 10, 0.0433 and 12, respectively. The Nusselt number and friction factor of the artificially roughened absorber plates has been determined experimentally and corresponding values were compared with that of the smooth duct for the range of flow Reynolds number 4000–18,000. The maximum enhancement in Nusselt number was reported for relative gap width of 4 and Number of gaps of 3. The thermohydraulic enhancement factor was found to be in order of the 1.54–2.39.

Recently, hydrodynamic interaction between two vessels in a side-by-side configuration has become a research focus. Because of the interaction of multiple bodies, the fluid movement and responses of the vessels are complex. First, the hydrodynamic performances of two identical barges in close proximity in a side-by-side configuration are numerically investigated with a wave elevation in between the barges. Second, corresponding experiments are carried out to validate the numerical results, and comparison of the experimental and calculation results shows that the numerical calculation accurately predicts the resonance period despite a difference in the peak values. Both fixed barges and barges undergoing constrained motions are also compared with free-floating barges to illustrate the influence of motion on the wave elevation and resonance phenomena. Sensitivity analyses of the gap width, barge length, barge breadth, and draft are performed, revealing that the resonant wavelength increases with increasing ...

Ultrasound, closed-circuit television (CCTV) and Panoramo (R) are capable of inspecting drinking water pipes and joints of any pipe material. The three tools were tested for their accuracy and reproducibility for gap width sizing in double-socket push-fit joints. The tests were performed at laboratory scale (PVC pipes and joints) in the field (asbestos cement pipes and joints) and in three full-scale tests (PVC) inside pipes used to supply drinking water. In the laboratory tests both accuracy and reproducibility were evaluated. In the field and full-scale tests only reproducibility of the tools was tested. CCTV proved to be the most accurate and reproducible for the application. This straightforward approach is considered to be a surrogate measure for joint's condition.

The purpose of this research is to improve the low-cycle fatigue life of the buckling-restrained brace (BRB) for the development of the high-performance buckling-restrained brace (HPBRB) used in bridge engineering. The HPBRB is expected to suffer three strong earthquakes without severe damage during the lifecycle of a bridge. This article employs a low-cycle fatigue experiment, including two series of BRB specimens, all of which had been tested to failure. In the second batch, the weld toes of the rib had been ground to improve the weld's low-cycle fatigue life. According to test results under constant and variable strain amplitudes, the specimens have a great low-cycle fatigue performance. The weld of the rib clearly affects the performance of the as-welded specimens tested with the relatively small strain amplitude. The toe-finished method effectively improves the BRB's low-cycle fatigue performance. Besides, the in-plane gap width of the BRB slightly affects the low-cycle fatigue life. Finally, the low...

A gap between two materials is a critical problem for friction stir welding (FSW). It is generated by a mismatch at the interface between two materials and causes defects and porosities due to the lack of material in the joint. In this study, friction powder processing (FPP) is proposed to solve this problem. Metal powder is first added to the gap between and then the FSW is performed. The effect of the gap width on the joint properties was first investigated, and the FPP feasibility was then assessed by adding pure Al powder to the gap between A1050-H24 plates. In addition, the mechanical properties and microstructures were investigated when adding a dissimilar powder, such as Cu powder, to the gap between Al plates. When using pure Al powder, the formation of defects is prevented. When using pure Cu powder, Al2Cu precipitates were formed in the stir zone, and consequently, the hardness significantly increased.

The objective of this study is to propose a scale-up factor for a mean drop diameter in batch rotor.stator mixers. We define a homogenization index (H.I.) as a scale-up factor obtained from a local energy dissipation rate of turbulence and a circulation number. The local energy dissipation rate is calculated using the volume of the homogenization region, and the local power consumption is obtained from the measured net power consumption and the flow rate.We also measure the mean drop diameter using certain time interval for different configurations of mixers and different operating conditions in order to evaluate the validity of the scale-up index using H.I. Experimental results show that H.I. could well account for the mean drop diameter under different rotor speed conditions (13–27 m/s), with a different gap width between the rotor and the stator (0.15–0.25 mm) and different sizes of mixers and production volume (rotor diameters were 30 and 57 mm; production scale was 1.5 and 9 L). These results indicate that H.I. can be used to predict the mean drop diameter. Our results also suggest that the scale-up criteria for the mean drop diameter in relation to mixing time is based on H.I., and not necessarily on geometrical similarities, same rotor tip speed, or gap width in the case of similar mixer configurations and our experimental range (1 to 10 L) used for our model product, which is similar to typical dairy foods.

Studies were carried out on coating glass beads with fine hematite particles by use of the theta composer, a newly developed high-shearing-type mixer. Topics of study included the effects of rotational speed of the rotor, N r , (i.e., tangential velocity of the rotor tip, vr ), and a gap width between the rotor and the wall of the vessel, l, on the coating process. The amount of hematite particles deposited on glass beads was plotted versus a parameter that relates a cumulative shear force acting on particles over a coating period t. All experimental data could be fitted by a single curve, and the parameter e was found to describe the coating process in the theta composer. Compression of core particles by the rotor was also analyzed using a 3-D DEM simulation. Average contact force by the rotor was found to be proportional to vr and inversely proportional to l. Thus, a cumulative shear force acting on a core particle is proportional to (vr /l)(vr t) after the particle passes through the gap N r t times. R...

‘Supply Air’ windows work as a heat reclaim device by intercepting a substantial proportion of incident solar energy as well as entraining beat escaping from rooms. This series of experiments was to determine if laminar flow could be achieved with a constant gap width across the range of window sizes commonly manufactured for domestic use. Ue-values were calculated from whole test cell energy balances during the day (the windows being un-shaded) and at night time the pressure-controlled vents were also tested for their effectiveness at regulating airflow through the window. Two windows of different aspect ratios were tests. Both achieved very low Ue-values with statistical upper limits of 0.6 and 0.5 W/m2K.

(2001). Arc sensor for simultaneous detection of torch aiming deviation and gap width. Development of high‐frequency oscillation arc (2nd report) Welding International: Vol. 15, No. 12, pp. 952-964.

A measurement of neutron dose rate on iron-polyethylene shielding structure was carried out by 252Cf source. Simulated geometry was slit-like opening of polyethylene in iron slab and polyethylene slab shielding.These experiment was done at research facility of Hazama Co,. Iron slab and polyethylene slab thickness were 10 cm each. A gap of the polyethylene was simulated. Neutron REM-counter, polyethylene covered BF3 counter (STUDSVIK 2202-D), was used for measurement of streaming neutron dose equivalent. The solid state track detector (SSTD), allyl-diglycol-carbonate, were used for measurement of fast neutron dose equivalent in the range of 170Kev to 15Mev.The experimental data was obtained against gap width, source location and detector location.Obtained data shows strong correlation between dose rate and above parameters.These data was investigated in the view of to make use of actual facility design and compared with calculation such as MCNP4B.From the result of gap streaming experiment and calculation,...

In many fields of industrial application the usage of ozone is a question of economics. In order to improve the efficiency of especially air-fed ozone generators, fundamental research work on modelling of microdischarges, the chemical reaction scheme, and extensive experimental investigations have been undertaken. By proper choice of the operation conditions like pressure, gap width, and cooling conditions, the efficiency can be improved considerably. The reaction temperature in the process volume and the concentration of nitrogen oxides are the main factors influencing the ozone yield.

The purpose of the present work was to investigate a possible relationship between the composition of composite restorative resins and their wall-to-wall polymerization contraction. The investigated brands contained bis-gma diluted with varying amounts of one or two low-viscous monomers. The wall-to-wall contraction was measured microscopically as the maximum gap width in the dentin part of cavities in extracted human teeth. A positive correlation between gap width and amount of diluting monomer was found, with commercial composites and with non-composite, experimental resins. Addition of up to 75 ° by weight of an inorganic filler to a monomer mixture similar to those found in commercial composites had no effect on the width of the contraction gaps. With non-composite experimental resins the gaps were found to increase with the amount of catalyst.It was concluded that the composition of the organic phase is of primary importance for the size of the wall-to-wall contraction of composite restorative resins.

Natural convection mass transfer at the inner surface of the outer cylinder of annuli was investigated using an electrochemical technique involving the deposition of copper from acidified copper sulphate solution. Variables studied were: annulus height, annular gap width and physical properties of the solution. Mass transfer data for annuli of large gap width (L/d ≤ 3.225) were correlated by the equation: For annuli of small gap width the data were correlated by the equation

Equations for natural convective mass transfer in short vertical annuli are proposed using equivalent diameter as the characteristic length parameter. Data for annuli of large gap width (de/L ≥ 0.62) are correlated by the equation: and those for small gap width (deL>0,62) by

Optical investigations were performed to prove the idea of variable pitch in the Grandjean structure of cholesteric liquid crystals. According to this model, the helical structure is deformed in such a manner that with decreasing thickness of the wedge-shaped layer the pitch of the screw decreases, while the number of turns remains constant. At the next “step”, however, the pitch gets large again and the number of turns decreases by a half. From measurements on the Grandjean structure with several derivatives of cholesterol, the values of the pitch are determined as a function of temperature and found to be in good agreement with values obtained from the wavelength at maximum reflection. This is considered as a confirmation of the model used, in particular of the assumption that the gap width is essentially equal to an integer multiple of the half pitch and the number of turns changes by one half at the optically observed discontinuities.

The thermal effects of different types of void volumes within a fuel pin, such as porosity, central void, and the gas gap between fuel and clad are examined. A new general relation for the dependence of thermal conductivity on the closed porosity is deduced. For given gas contents and specific ranges of pore temperatures and sizes, a simple approximate equation is set up, which is in good agreement with experimentally obtained results. A central void is very effective in reducing the maximum temperature; and its use implies a considerable increase in linear pin power. In-pile migration of the porosity in the hotter regions of oxide fuel pins forms or increases the central void and densifies the hotter region. This effect is calculated in a two-zone porosity model. For a uniform gap between fuel and clad, the temperature drop is calculated as a function of gap width, linear pin power, inner temperature of clad, inside radius of clad, emissivities of surfaces, and types of gas within the gap, such a...

When vertical slat snow fences were built with gaps of 1, 2, and 4 feet below 6 feet of fencing, maximum snow depth and maximum snow volumes were found in the lee drifts behind the fences with the 1-foot gap. As gap size increased, maximum snow depth moved farther from the fence and decreased. The volume of snow in the lee drifts behind fences with 2- and 4-foot gaps was about the same, but amounted to only a little over one-half that behind fences with 1-foot gaps. The 1-foot gap became plugged with snow even in the below-average snow year studied. This caused maximum snow depths to move toward the fence.