Liquid-metals mass transfer

Liquid metals mass transfer. In recent years several correlations for mass-transfer coefficients of liquid metals have appeared in the literature. It has been found (Gl) that with moderate safety factors, the correlations for nonliquid metals mass transfer may be used for liquid metals mass transfer. Care must be taken to ensure that the solid surface is wetted. Also, if the solid is an alloy, there may exist a resistance to diffusion in the solid phase. 

Further information on liquid-metal heat transfer in tube banks is given by Hsu for spheres and elliptical rod bundles [Int. J. Heat Mass Transfer, 8, 303 (1965)] and by Kahsh and Dwyer for oblique flow across tube banks [Int. ]. Heat Ma.ss Transfer, 10, 1533 (1967)]. For additional details of heat transfer with liqmd metals for various systems see Dwyer (1968 ed., Na and Nak supplement to Liquid Metals Handbook) and Stein ( Liquid Metal Heat Transfer, in Advances in Heat Transfer, vol. 3, Academic, New York, 1966). 

Liquid-gas-solids mixing 275 Liquid-liquid extraction, mass transfer 599 Liquid metals, heat transfer 523 meters 269... 

Kutateladze, S. S., 1961, Boiling Heat Transfer, Int. J. Heat and Mass Transfer 4, 31-45. (4) Kutateladze, S. S., V. M. Borishansky, I. I. Novikov, and O. S. Fedyaskii, 1958, Liquid Metal Heat Transfer Media, Atomnaya Energiva (Moscow) Supplement No. 2, Translated by Consultants Bureau, Inc., New York (1959). 

This example illustrates the distillation of a binary mixture in an open-batch distillery with flowing sweep gas and pervaporation by having a porous plate floating on top of the liquid hold up, as shown in Fig. 4.20. The porous plate was made from inert sintered metal with various pore sizes between 100 and 1 mfi, and had a thickness of 1 mm. The porosity was 40 % and the tortuosity factor was about 2. This results in an effective liquid phase mass transfer coefficient of about hiq = 2 X 10-7 m s-i, which results in Kiiq = 1.9 X 10 22. Therefore, one would expect the distillation process to be nonselective - that is, Si = xi - xi = 0. 

Lee, S., Liquid Metal Heat Transfer in Turbulent Pipe Row with Uniform Wall Rux , Int. J. Heat Mass Transfer, Vol. 26, pp. 349-356,1983. 

Although the term mass transfer as used in liquid metal technology normally refers to the phenomenon described above, a second type of mass transfer has been observed in isothermal liquid metal systems due to the presence of more than one container metal or alloy. For example, nickel will transfer to and deposit on molybdenum in sodium at 1800°F and will dissolve from type 304 stainless steel to precipitate on iron in lithium at 1800°F. The possibility of such dissimilar metal mass transfer must be considered every time an additional material is proposed for use in an engineering system as a valve seat, impeller bearing, and so forth. Not much data are available on usable material combinations, and the tendency is to design for a single container alloy whenever possible. 

Chen and Vallabh (47) have obtained data on gas holdup and liquid side mass transfer coefficients from 68 to 144 mm i.d. columns using cylindrical (0.5 in and 1 inch) screen packings (e = 0.97). Sahay and Sharma (45) have reported a detailed study for 100 to 380 mm i.d. columns with packings of different sizes and shape (ceramic, plastic, metal). Recently Sawant et al. (48) reported results concerning wire gauze packings (diameter equal to the inner diameter of the column - c = 0.95) in 100 and 200 i.d. columns. All these data may be regrouped in Fig. 9 (48). It may... 

Static isothermal capsules are also useful for studying dissimilar metal mass transfer. DiStef o [79] studied the interactions of type 316 stainless steel with niobium or Nb-1 % Zr in Na and NaK by exposing tension specimens of the niobium or Nb-1 % Zr to the liquid metal in a stainless steel container (Fig. 10). A transfer of carbon and nitrogen from the stainless steel to the niobium or Nb-1 % Zr was noted. The carbon and nitrogen transfer depended on temperature, time, and the surface tirea ratios of stainless steel to niobium (varied by changing the number of spacers shown in Fig. 10). 

Static capsules of the type shown in Fig. 9 are used to determine the extent of solid dissolution, interstitial transfer, or interalloying between the solid and liquid. The capsule can serve as the test specimen, or the test specimen can he incorpforated as an insert in the capsule. In the latter case, it is a general requirement that the capsule and test specimen be of the same composition unless the test is intended specifically to study dissinular-metal mass transfer effects. Incorporation of a test specimen simplifies the determination of any changes in weight, dimension, or mechanical properties due to liquid metal exposure. 

Bulk Liquid Membranes (BLM). This is the simplest type of liquid membrane (2-8) and is utilized for fundamental studies of certain aspects of liquid membrane transport processes. In one such process, a beaker-in-a-beaker cell (Figure 1) consists of inner and outer compartments which contain the aqueous feed (F) and strip (S) solutions, respectively. The inner beaker contains the stripping solution and is surroimded by the feed solution. Both aqueous solutions contact the upper organic layer, which is the liquid membrane. Mass transfer takes place from the feed solution through the liquid membrane and into the strip solution. Bartsch et aL studied the transport of alkali metal cations across bulk liquid membranes in which a crown ether carboxylic acid in the organic layer served as the carrier (2,3). 

Fig. 20. Improved packing parameters ( ) for liquid mass transfer (a) ceramic Raschig rings (b) metal Raschig rings (c) ceramic Bed saddles (d) metal PaH...

In a number of reflning reactions where bubbles are formed by passing an inert gas tlrrough a liquid metal, the removal of impurities from the metal is accomplished by transfer across a boundaty layer in the metal to the rising gas bubbles. The mass uairsfer coefflcient can be calculated in this case by the use of the Calderbank equation (1968)... 

Figure 9-6T. (Top) Cascade Mini-Ring, (metal and plastic). Originally used by permission of Mass Transfer, Inc., now, Glitsch, Inc. (middle and bottom) Elevation and plan views of Ballast rings (right) and Cascade Mini-Rings (left). Note how high aspect ratio of former permits occlusion of interior surfaces. Low aspect ratio of Cascade Mini-Rings, on the other hand, favors orientation that exposes internal surfaces for excellent film formation, intimate mixing, and gas-liquid contact. Used by permission of Glitsch, Inc. Bull. 345.

Mass-transfer deposits can lead to blockages in non-isothermal circulating systems, cis in the case of liquid-metal corrosion. In fused salts, the effect can be reduced by keeping contamination of the melt by metal ions to a minimum e.g. by eliminating oxidising impurities or by maintaining reducing conditions over the melt . 

Mass transfer This phenomenon manifests itself as the physical transport of a metal from one portion of the system to another, and may occur when there is an alloy compositional difference or a temperature gradient between parts of the unit joined by the flowing liquid phase. An exceedingly small solubility of the metal component or corrosion product in the molten metal or salt appears sufficient to permit mass transfer to proceed at a fairly rapid pace. 

In general, it is fair to state that one of the major difficulties in interpreting, and consequently in establishing definitive tests of, corrosion phenomena in fused metal or salt environments is the large influence of very small, and therefore not easily controlled, variations in solubility, impurity concentration, temperature gradient, etc. . For example, the solubility of iron in liquid mercury is of the order of 5 x 10 at 649°C, and static tests show iron and steel to be practically unaltered by exposure to mercury. Nevertheless, in mercury boiler service, severe operating difficulties were encountered owing to the mass transfer of iron from the hot to the cold portions of the unit. Another minute variation was found substantially to alleviate the problem the presence of 10 ppm of titanium in the mercury reduced the rate of attack to an inappreciable value at 650°C as little as 1 ppm of titanium was similarly effective at 454°C . 

Table 3.1 shows the kinetic parameters for cell growth, rate models with or without inhibition and mass transfer coefficient calculation at various acetate concentrations in the culture media. The Monod constant value, KM, in the liquid phase depends on some parameters such as temperature, initial concentration of the carbon source, presence of trace metals, vitamin B solution, light intensity and agitation speeds. The initial acetate concentrations in the liquid phase reflected the value of the Monod constants, Kp and Kp. The average value for maximum specific growth rate (/xm) was 0.01 h. The value... 

Other samples examined to date have included mass-transfer inclur s from liquid metal cooling systems, titanium alloy phases, and interm c... 

If the accommodation coefficient CA is equal or close to unity for liquid metals, as appears most likely for clean systems, then bubble growth in such liquids is little affected by mass transfer effects. It has been illustrated that the growth rate curves for CA = 1 and CA = are not very far apart. 

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