Visualisation research on characteristics of the cryogenic slug flow in vertical and inclined tubes

The statistical parameters of Taylor bubbles in cryogenic slug flow along glass tube were studied experimentally for various inclination angles θ (0°–60° from the vertical direction) and four tube inner diameters D (14, 18, 25 and 32 mm) by using high speed digital camera. The distributions and mean values of initial formation position, and the length and velocity of Taylor bubbles along the tube at various inclination angles were obtained. Initial position of Taylor bubbles increases as tube inner diameter increases and the effect of tube diameter on Taylor bubble initial position becomes more obvious at θ ≥ 30°. Taylor bubble length shows an allometric decreasing trend with the increasing of tube inner diameter. The influence of inclination angle and axial position on the length and velocity of Taylor bubble in cryogenic slug flow agrees qualitatively with conventional air–water system. The maximum mean velocity of Taylor bubble occurs at 30° ≤ θ ≤ 45° and the minimum mean length of Taylor bubble occurs at 0° ≤ θ ≤ 20°. The Mean length of Taylor bubble increases along the tube for x/D ≤ 60. © 2011 Canadian Society for Chemical Engineering     

A study of the separation efficiency of wired thermal diffusion columns with tubes rotating in opposite directions

Rotating the tubes oppositely in a wired concentric-tube thermal diffusion column substantially increases the separation efficiency by improving the cascading effect. Considerable improvement in separation was obtained by employing the rotating wired column, operation at the best tube-speed of rotation and the best wire-angle of inclination instead of using the stationary column without a wire spiral.     

ENRICHMENT OF HEAVY WATER BY THERMAL DIFFUSION

Equations of the best wire angle of inclination for the maximum separation, maximum output and minimum column height for enrichment of heavy water in a concentric-tube wired thermal diffusion column have been derived. Considerable improvements in performance were obtained by employing the wired column instead of using the open column (without wire). It was also found that the wire inclination for maximum separation is also the wire inclination required to obtain the maximum production rate, or minimum column height, for a specified degree of separation.     

The best performance of spiral wired thermal diffusion columns of the frazier scheme

Equations have been derived for the optimum wire angles of inclination for maximum separation, maximum production rate and minimum column height in the Frazier scheme of concentric‐tube thermal diffusion columns with a tight fitting wire spiral, having a diameter equal to the annular spacing, and wrapped on the entire inner tube. Considerable improvement in performance is obtained when a Frazier scheme is operated at the optimum corresponding wire angle of inclination, especially for the scheme of high column number.     

The Enrichment of Heavy Water in a Continuous-Type Inclined Thermal Diffusion Column

Abstract

Equations of the best angle of inclination and the maximum separation for the enrichment of heavy water in a continuous-type inclined thermal diffusion column have been derived. Considerable improvement in separation was obtained by employing the inclined column instead of using the Clusius-Dickel column.     

Particle Chromatographic Separation of Coal Fly Ash

Abstract

Attempts were made to totally separate the 13 types of particles in a coal fly ash. While a considerable separation was obtained, it was far from complete even with optimal operating conditions. The best results were obtained with camphor as the host material in the tilt rotating zone melting technique with a tube rotation rate of 25 rpm and a tube tilt angle of 30° to the horizontal. Additional zone passes improved the separation only slightly. The zone travel rate at which each particle type was trapped, and the length over which each type was trapped, both increased as the tube rotation rate was increased and as the tilt angle was decreased. If a bubble contacted the interface during horizontal operation, the trapping occurred at significantly lower freezing rates and the separation was considerably worse. The smaller particles were trapped at lower freezing rates than larger particles. Naphthalene and biphenyl proved to be poor hosts because of extensive bubble formation at the interface during zoning. Particles were trapped at impractically low freezing rates with Salol.     

The best performance in spiral wired thermal diffusion columns

The Improvement in performance of a concentric tube thermal diffusion column by means of a wire spiral, having a diameter equal to the annular spacing and inserted as a spacer in the annular region, was investigated. Equations of the optimum wire angle of inclination from the vertical for the maximum separation, maximum output and minimum column height have been derived. Considerable improvements in performance are obtainable if the spiral wired columns are employed, instead of using the open column (without wire), so that the convection strength can be reduced and controlled, resulting in suppressing the undesirable remixing effect while still preserving the desirable cascading effect.     

THE BEST PERFORMANCE IN SPIRAL WIRED THERMAL DIFFUSION COLUMNS

The Improvement in performance of a concentric tube thermal diffusion column by means of a wire spiral, having a diameter equal to the annular spacing and inserted as a spacer in the annular region, was investigated. Equations of the optimum wire angle of inclination from the vertical for the maximum separation, maximum output and minimum column height have been derived. Considerable improvements in performance are obtainable if the spiral wired columns are employed, instead of using the open column (without wire), so that the convection strength can be reduced and controlled, resulting in suppressing the undesirable remixing effect while still preserving the desirable cascading effect.     

Generation of Variance, “Theoretical Plates,” Resolution,and Peak Capacity in Electrophoresis and Sedimentation

Abstract

The rate of generation of variance, dσ²/dX, is a fundamental parameter which determines peak or boundary width and, thus, resolution in many differential migration systems. This parameter can be identified with the “plate height” of chromatography. By extending this nomenclature and the underlying concepts to electrophoresis and sedimentation, we arrive at parameters, particularly the “number of theoretical plates,” which allow a comparison of the effectiveness of these diverse methods. Equations are derived for the plate number as well as for resolution and peak capacity. Numerical comparisons are shown. Optimization is discussed with reference to maximum resolution, peak capacity, and separation speed.     

Effluent treatment using a bipolar electrochemical reactor with rotating cylinder electrodes of woven wire meshes

BACKGROUND: The behaviour of a bipolar electrochemical reactor consisting of one or more rotating cylinder electrodes of woven wire meshes is reported using copper and cadmium deposition from dilute solutions as test reactions. RESULTS: The best performance related to electrode number was determined for copper deposition and was achieved by an arrangement with two bipolar electrodes, for which the conversion in a single pass was approximately 47%. The specific energy consumption was 3.27 kWh kg^?1 with a normalised space velocity of 23.05 h^?1. The copper powder obtained showed a nodular and dendritic surface morphology. This reactor configuration was also analysed for cadmium deposition, in which hydrogen evolution takes place simultaneously as a side cathodic reaction, considering the effect of flow rate and total current. The maximum conversion per pass for cadmium removal was 38.91%. In this case the reactor with two bipolar electrodes showed a performance similar to that of a monopolar reactor operated at a rotation speed three times higher. CONCLUSION: A continuous electrochemical reactor with two rotating bipolar electrodes of woven wire meshes presents a good performance for copper or cadmium removal from dilute solutions. Copyright © 2009 Society of Chemical Industry     

环形通道内置螺旋线圈过冷流动沸腾传热特性

研究了置有螺旋线圈的内管加热环形通道中水的过冷流动沸腾传热特性。环形通道由铜制加热棒外套石英玻璃管构成,不同螺旋节距和线丝直径构成的5种螺旋线圈用于实验。对每种置入螺旋线圈管和光滑管分别进行了不同质量流速和热负荷下的16组实验,分析了线丝直径和线圈节距对传热系数的影响规律及机理。结果表明,螺旋线圈存在能使流体发生旋转分离,且使汽化核心密度增大,从而有效强化过冷沸腾换热;传热系数随着线圈节距的减小、线丝直径的增加,即节径比(P/e)减小而增大,当P/e最小为1.5时强化效果最好;最佳强化换热性能较光滑管的高出109%。将实验数据与4个经验关系式的预测值进行了比较,并给出了不同工况下各实验管的强化系数对比。     

Heat transfer with coiled wire turbulence promoters

An experimental study of forced convection heat transfer and frictional power loss for water flowing in a vertical tube is reported in this paper. The study investigates the effect of coiled wire turbulence promoters of various pitch to diameter ratio (1.00–5.50) upon the Nusselt Prandtl modulus Nu/Pr^1/3 and Fanning friction factor C_f for three different wire diameters, 0.052-in., 0.063-in. and 0.072-in. Analysis of the computed results indicates that heat transfer increases by as much as 280%, though at the cost of much larger increase in frictional power loss. Consequently, coiled wire turbulence promoters can be used with advantage for cases where pumping power is not the dominating factor and reduction in weight and size of the equipment is more important. The present results and those of three previous investigations of heat transfer in tubes with coiled wire turbulence promoters were satisfactorily correlated by the expression which was found to be independent of the tube diameter, wire diameter, pitch to diameter ratio and the test fluid.     

Influence of Stirring on Incorporation of Particles during Solidification

Abstract

The critical freezing rate V_c was measured for glass beads suspended in naphthalene by using the tilt rotating zone melting technique. In horizontal operation with a large gas bubble sweeping along the interface during rotation, V_c increased dramatically with increasing tube rotation rate and decreasing mass of beads. Tilting the tube prevented the bubble from contacting the freezing interface and very stongly increased V_c . Siliconized glass beads were pushed as well as nontreated beads, both in horizontal operation with tube rotation and in vertical operation without stirring. Teflon particles were pushed to very high freezing rates in the horizontal rotating configuration. These results differ from those of Omenyi and Neumann, who predicted and observed that both Teflon and siliconized glass beads are not pushed by freezing naphthalene at any freezing rate.     

倾斜管内低温液弹和Taylor汽泡的长度分布

An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in an inclined tube with closed bottom by using a high speed motion analyzer.The experimental tube is 0.018 m ID and 1.0 m in length.The range of the inclination angle is 45°-90° from the horizontal.The experiment focused on the effect of the inclination angle show that the mean liquid slug length and Taylor bubble length increase with the increasing x/D at various inclination angles.At the same x/D,the mean liquid slug length and Taylor bubble length increase first,and then decrease with decreasing inclination angles,with the maximum at 60°.In the vertical tube,standard deviation of the nitrogen Taylor bubble length increase with the increasing x/D.For the inclined tube,standard deviation of the nitrogen Taylor bubble length increases first,and then decreases with the increasing x/D.Standard deviation of the liquid slug length increases with increasing x/D for all inclination angles.     

Performance analysis of an integrated tangential microfilter‐fermenter

A specially designed bioreactor including an axial microfilter for cell retention was evaluated for continuous‐flow operation with selected liquid media as controls and in aerobic cultivations of Saccharomyces yeasts. In the initial tests, performance characteristics such as filtration rates and cell accumulation were assessed as a function of filter rotational speed, operating pressure, cultivation time and microfilter type (i.e. membrane or porous metal). The bioreactor did not perform satisfactorily when viscous extracellular polymer was present in the liquid. In the continuous‐flow culture enabling cell retention, Saccharomyces cerevisiae yeast cell concentrations were enhanced by as much as 16‐fold over ordinary batch growth. Concomitant filtration rates were stable over operating times of up to 130 h and hence were independent of the cell concentration. The maximum steady‐state flux was enhanced at rotational speeds up to 400‐700 rpm ranging from 22 to 42 L m^?2 h^?1. Higher rotation rates offered no further improvements. The maximum stabilized flux was independent of operating pressure. Pressure increases caused momentary flux improvements, which rapidly declined and eventually restabilized. Copyright © 2006 Society of Chemical Industry     

Cation-Exchange Separation of Scandium from the Rare-Earth Elements

Abstract

From certain organic solvents containing organic phosphorus compounds such as trioctylphosphine oxide (TOPO), bis(2-ethylhexyl)orthophosphoric acid (HDEHP), or tri-n-butylphosphate (TBP) and hydrochloric acid, scandium is much less retained on the strongly acidic cation-exchange resin Dowex 50 than are all other members of the rare-earth group. Thus on this resin in a medium which is 95% tetrahydrofuran, 5% 6 M hydrochloric acid, and 0.1 M TOPO, the separation factor for scandium-rare earths is greater than 4 × 10³ (corresponding to distribution coefficients of < 1 for scandium and >4 × 10³ for all the other rare-earth elements). By the use of this system a complete and highly effective separation of tracer and macro quantities of scandium from the rare earths can be achieved on a column of this exchanger. Among the organic solvents investigated, tetrahydrofuran gives the best results. The effectiveness of the organic extractants increases in the order TBP < HDEHP < TOPO     

Hay Component Sieving by a Rotary Sieve with Lifting Flights

In order to improve drying of hay-composed materials, the already dried parts must be extracted from the mixture to save energy and avoid quality problems. A separation test of a mixture of leaf and stems of ryegrass and clover for hay was developed for this, using a rotary sieve with lifter flights and the vegetal material at several moisture contents. The best separation results were found for the dried state and rotation speed of 2.1 sec^?1. The stems' separation efficiencies were between 74 and 96%.     

Synthesis of Extraction Resin Containing N,N,N′,N′-Tetraisobutyl Diglycolamide and its Application for Separation of Sr(II) from Rb(I)

Abstract

A novel Levextrel resin containing N,N,N′,N′-tetraisobutyl diglycolamide (TiBDGA) was synthesized by suspension polymerization of styrene and divinylbenzene and its performance for separation of Sr(II) from Rb(I) was investigated. The effects of crosslink degree, stirring speed, and the ratio of porogenic-agents on the resin synthesized were examined. The optimum TiBDGA resin with 40 wt.% divinylbenzene as cross linking agent and 20 wt.% of n-octanol as porogenic-agents provided excellent adsorption capacity of 22.5 mg/g. The distribution coefficient (K _d) of Sr(II) in HNO₃ media onto the resin depended heavily on the acidity in the aqueous solution. The maximum K _d for Sr(II) (7300 mL/g) was observed when the HNO₃ concentration in aqueous phase reached 2 mol/L. The difference in the Sr(II) and Rb(I) distribution coefficients of several orders of magnitude implied that ⁸⁹Sr may be separated from ⁸⁶Rb with a radionuclide purity greater than 99%. And the maximum static adsorption capacity of Sr(II) on the resin was 22.5 mg/g.     

Particle Chromatography Using Naphthalene as a Host

Abstract

Separation of metal and charcoal particulate mixtures suspended in naphthalene has been studied by accelerated directional solidification of the naphthalene, using the vertical Bridgman (VB) technique and tilt rotation zone melting (TRZM). In VB the separation was limited to monolayers of particles resting on the interface. An extent of separation ranging up to 68% was obtained by a single TRZM pass. However, the near-perfect separations thought to be possible were not obtained because of catastrophic trapping of particles in irregular mixed bands. Trapping, and perhaps separation as well, is enhanced by the presence of a large gas bubble sweeping the freezing interface (due to tube rotation)     

Probability of Trapping Solid Particles during Zone Melting

Abstract

The probability P of trapping of glass beads was measured for tilt rotating zone melting of camphor. P increased with increasing zone travel rate, increasing tilt angle, decreasing tube rotation, and increasing mass of beads. P also decreased dramatically with distance down the tube. This is attributed to increasing impurity content as the zone moves down the tube and by the changing shape of the freezing interface due to the diminished content of glass beads. Trapping was predominantly by periodic bands, indicating one or more catastrophic trapping mechanisms.