Liquid coefficients

Dengler and Addoms 8 measured heat transfer to water boiling in a 6 m tube and found that the heat flux increased steadily up the tube as the percentage of vapour increased, as shown in Figure 14.4. Where convection was predominant, the data were correlated using the ratio of the observed two-phase heat transfer coefficient (htp) to that which would be obtained had the same total mass flow been all liquid (hi) as the ordinate. As discussed in Volume 6, Chapter 12, this ratio was plotted against the reciprocal of Xtt, the parameter for two-phase turbulent flow developed by Lockhart and Martinelli(9). The liquid coefficient hL is given by ... 

Rohrschneider, L. Solvent characterization by gas-liquid coefficients of selected solutes. Anal Chem., 45 (7) 1241-1247,1973. Romero Taboada, E., Barifouse M.M., Rasero, F.S., Pena, H.A., de laColina, G.C., and Dios. C.G. Fate of methabenzthiauron in calcareous soils from southeastern Spain, J. Environ. Qua ., 26(2) 466-471,1997. 

In practice, whether the cell is stirred or not, transfer is conveniently referred to over-all rather than interfacial concentrations. The over-all transfer coefficient K is related to the individual liquid coefficients by the relations... 

There are two mass transfer coefficients that are significant, the gas/liquid mass transfer coefficient and liquid to solid coefficient. If the gas is a mixture, the gas/liquid coefficient is more difficult to estimate. 

Mass-transfer coefficient models for the vapor and liquid coefficients are of the general form... 

The overall volumetric heat transfer coefficient is obtained by combining a gas and liquid coefficient. Woods provides a value of 3 kW/m °C for a typical volumetric overall heat transfer coefficient for a packed tower under the above conditions (see Table 3-18). For greater accuracy values for the individual gas and liquid volumetric heat transfer coefficient may be obtained using the relations... 

Either the nucleate-boiling correlation given by Equations (6.92a) and (6.92b) or the extended methods given in the literature [34, 47] can be used for The two-phase convective coefficient is related to the single-phase liquid coefficient heo by... 

As one might expect, these are conveniently subdivided into correlations for gas-liquid coefficients and for liquid-solid coefficients. The overall structure of these correlations is not much different from those we have seen for other multiphase reactors, but the correlation coefficients, of course, are very-specific to the application. 

These equations enable the evaluation of balanced distribution of the nonpolar component i between different media due to mass transfer. In the absence of the subsurface gas or nonpolar liquid coefficients a and/or a... 

The heated gas coefficients were determined in the same manner as the subcooled liquid coefficients. For each heated gas data point, a corresponding model generated saturated bubble point was calculated at each liquid temperature. For a given screen, pressurant gas, and cryogenic liquid, the heated gas loss, defined as the ratio of bubble point pressures ... 

Mass transfer coefficients for gas to liquid are usually smaller than for liquid to solid mass transfer in low velocity pilot plants but are higher at the higher velocities in commercial units. In either case, however, gas-liquid mass transfer is usually not limiting. As part of a study of formic acid oxidation in a laboratory trickle bed. Goto and Smith [19] showed that at low gas velocities (0-0.8 cm/s), the gas-liquid and liquid-solid mass transfer are comparable for a 0.5 mm particle. For a 2 mm particle, the gas-liquid coefficient is about three times the solid-liquid coefficient. 

Grashof number, Gr gp L pAT p,Lu - L characteristic length dimension density of liquid coefficient of thermal volume expansion / buoyancy force V viscous force / Free convention heat transfer... 

In equations 1-9 and 1-10, y and x refer to the mole fractions of solute in the gas and liquid streams, respectively, and Lm and represent the molar values of liquid flow rate and density, i.e., lb moles/(b)(sq ft) and lb moles/cu ft. The subscript 1 refers to the bottom of the column, subscript 2 to the top of the column, and subscript e to the equilibrium conqmsi-tion with respect to the main body of the other phase. The other symbols have the same significance as in the previous equations. In general, it is preferable to enq>loy the overall gas-film coefficient when the gas-film resistance is predominant, and the overall liquid coefficient when the principal resistance to absorption is in the liquid phase. 

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