Liquid-side

U. Single water drop in air, liquid side coefficient / jy l/2 ki = 2 ), short contact times / J 1 lcontact times dp [T] Use arithmetic concentration difference. Penetration theory, t = contact time of drop. Gives plot for k a also. Air-water system. [lll]p.. 389... 

FIG. 13-36 Graphical solution for a column with a partially flashed feed, a liquid side-stream and a total condenser. 

Sinek and Young present a design procedure for predicting liquid-side falling film heat transfer coefficients within 20% and overall coefficients within 10%. 

Because the interface region is thin, the flux across a thin film will be at steady state. Therefore, the transfer rate to the gas-liquid interface is equal to its transfer rate through the liquid-side film. Thus,... 

Johnson et al. (J4) investigated the hydrogenation of a-methylstyrene catalyzed by a palladium-alumina catalyst suspended in a stirred reactor. The experimental data have recently been reinterpreted in a paper by Polejes and Hougen (P4), in which the original treatment is extended to take account of variations in catalyst loading, variations in impeller type, and variations of gas-phase composition. Empirical correlations for liquid-side resistance to gas-liquid and liquid-solid mass transfer are presented. 

Figure 8.4 Graph of temperature against molar volume (a), and density (b). for CO (gas) and C02 (liquid) in the temperature range from the triple point to the critical point. The dashed line in (b) is the average density. The area enclosed within the curves is a two-phase region, with the molar volume or the density of the gas and liquid at a particular temperature given by the horizontal (dotted) tie-lines connecting the gas and liquid sides of the curve.

Opposed signs of the normal to the interface surface on the liquid side and on the vapor side as well as conditions (8.6-8.8) and correlation... 

Fig. 10-18 A schematic of a stagnant boundary-layer gas exchange model. Cg = gas concentration at the liquid side of the interface Q = gas concentration at the base of the stagnant boundary layer Znim = stagnant boundary layer thickness.

Here, kg and ki are the gas-side and liquid-side mass transfer coefficients. Their units are identical to those for Kg and Ki, m/s. Like the overall coefficients, they are usually measured and reported as the composite quantities kgAj and kiAi with SI units of s. ... 

Solution gives T=51 trays. The indicated separation appears feasible in a bubble-cap column although the design engineer should not be content with the glib assumption of negligible liquid-side resistance. 

Surface Renewal Theory. The film model for interphase mass transfer envisions a stagnant film of liquid adjacent to the interface. A similar film may also exist on the gas side. These h5q>othetical films act like membranes and cause diffu-sional resistances to mass transfer. The concentration on the gas side of the liquid film is a that on the bulk liquid side is af, and concentrations within the film are governed by one-dimensional, steady-state diffusion ... 

Mass transfer in the continuous phase is less of a problem for liquid-liquid systems unless the drops are very small or the velocity difference between the phases is small. In gas-liquid systems, the resistance is always on the liquid side, unless the reaction is very fast and occurs at the interface. The Sherwood number for mass transfer in a system with dispersed bubbles tends to be almost constant and mass transfer is mainly a function of diffusivity, bubble size, and local gas holdup. 

The diffusivity in gases is about 4 orders of magnitude higher than that in liquids, and in gas-liquid reactions the mass transfer resistance is almost exclusively on the liquid side. High solubility of the gas-phase component in the liquid or very fast chemical reaction at the interface can change that somewhat. The Sh-number does not change very much with reactor design, and the gas-liquid contact area determines the mass transfer rate, that is, bubble size and gas holdup will determine reactor efficiency. 

In fact, the horizontal component of liquid surface tension, 7 cos 0, is not without effect, since the triple-line region now protrudes from the bulk solid. This component leads to a stretching of the surface layer of solid on the vapor-phase side of the triple line for 0 < tt/2 or on the liquid side for 0 > 77/2. By analogy with Eq. (8), we have a second contribution to the work effected, E2. 

Although the values of kba dr in the literature are reasonable and comparable each other, the different trend mentioned above may be due to the different operating conditions. The gas-liquid interfacial area(a) and liquid side mass transfer coefHcient(ki) have been determined from the knowledge of measured values of gas holdup and kcacir [11]- The values of a and ki increase almost linearly with increasing Ug or Ul- The values of h cir and ktacir in circulating beds can be predicted by Eqs.(ll) and (12) with a correlation coefBcient of 0.92 and 0.93,... 

The measurement of liquid side gas - liquid mass transfer coefficient kia, showed that the value of kia increase with increasing rotation speed (V) and gas flow rate (Qg). hi the present research, the effect of impeller rotation on mass transfer coefficient was more significant than the effect of gas flow rate. The following correlation was obtained kia =1.7 x 10 ... 

The impact process of a 3.8 mm water droplet under the conditions experimentally studied by Chen and Hsu (1995) is simulated and the simulation results are shown in Figs. 16 and 17. Their experiments involve water-droplet impact on a heated Inconel plate with Ni coating. The surface temperature in this simulation is set as 400 °C with the initial temperature of the droplet given as 20 °C. The impact velocity is lOOcm/s, which gives a Weber number of 54. Fig. 16 shows the calculated temperature distributions within the droplet and within the solid surface. The isotherm corresponding to 21 °C is plotted inside the droplet to represent the extent of the thermal boundary layer of the droplet that is affected by the heating of the solid surface. It can be seen that, in the droplet spreading process (0-7.0 ms), the bulk of the liquid droplet remains at its initial temperature and the thermal boundary layer is very thin. As the liquid film spreads on the solid surface, the heat-transfer rate on the liquid side of the droplet-vapor interface can be evaluated by... 

The molar transfer rate coefficient kG (gas side) or kL (liquid side) (m s-1) can be defined as the ratio between the intrinsic molecular diffusivity of the solute gas A in the gas or liquid matrix and the diffusion lengths dG or dL (Eqs. (2) and (3)). The diffusion lengths depend on the reactor flow and mixing properties. 

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