Liquid phase coefficient

A. Absorption, counter-current, liquid-phase coefficient Hi, Sherwood and Holloway correlation for random packings... 

For liquid metals the superiority of nucleate boiling heat transfer coefficients over those for forced-convection liquid-phase heat transfer is not as great as for ordinary liquids, primarily because the liquid-phase coefficients for liquid metals are already high, and the bubble growth period for liquid metals is a relatively short fraction of the total ebullition cycle compared with that for ordinary fluids. In the case of liquid metals, the initial shape of the bubbles is hemispheric, and it becomes spherical before leaving the heating surface. This is because of very rapid... 

Kg and Kl are known as the overall gas and liquid phase coefficients, respectively. 

Using this expression, the effective solid-phase diffusion coefficient is found to be equal to 3.46 X 10-10 m2/s. This coefficient is related to the liquid-phase coefficient as follows (eq. (3.602)) ... 

The film (individual) coefficients of mass transfer can be defined similarly to the film coefficient of heat transfer. A few different driving potentials are used today to define the film coefficients of mass transfer. Some investigators use the mole fraction or molar ratio, but often the concentration difference AC (kg or kmol m ) is used to define the liquid phase coefficient (m while the partial pressure difference A/i (atm) is used to define the gas film coefficient (kmolh m 2 atm ). However, using and A gp of different dimensions is not very convenient. In this book, except for Chapter 15, we shall use the gas phase coefficient (m h" ) and the liquid phase coefficient ki (m h ), both of which are based on the molar concentration difference AC (kmol m ). With such practice, the mass transfer coefficients for both phases have the same simple dimension (L T" ). Conversion between k and is easy, as can be seen from Example 2.4. 

In general, the rates of the mass transfer increase when it is accompanied by reactions. For example, if k indicates the liquid phase coefficient, including the effects of the reaction, then the ratio E can be defined as ... 

However, the sorption coefficient in Equation (2.67) is a liquid-phase coefficient, whereas the sorption coefficient in Equation (2.72) is a gas-phase coefficient. The interconversion of these two coefficients can be handled by considering a hypothetical vapor in equilibrium with a feed solution. This vapor-liquid equilibrium can then be written... 

In practically all the gas-bubble liquid systems, the liquid-phase mass-trans-fer resistance is strongly controlling, and gas-phase coefficients are not needed. The liquid-phase coefficients are correlated by (Hughmark, 1967)... 

A larger solvated volume and therefore a lower diffusion (through the liquid phase) coefficient. 

It is expected that a change in system pressure, and therefore the partial pressure of the solute, should have little effect on the liquid-phase coefficient. Although the solubility in the liquid phase is reduced with temperature increase, and the Henry s Law constant is greater, the liquid-film coefficient (Ll) may increase rapidly with temperature. Thus, there may exist an optimum temperature for a particular absorption sysr tern, which is not the lowest temperature, where solubility of the absorbed solute is greatest in the liquid phase. 

For Raschig rings and Berl saddles, Shulman and coworkers [107] have established the nature of the area-free mass-transfer coefficients by passing gases through beds filled with packings made with naphthalene, which sublimes into the gas. By comparing these with k a s from aqueous absorption [48] and other systems the interfacial areas for absorption and vaporization were obtained. The data on kj a" [106] then provided the correlation for k, the liquid-phase coefficient. Their work is summarized as follows. 

Solution From Table 8.2-2, we see that the units of the liquid-phase coefficient correspond to k. Thus... 

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