Gas phase transfer

Gj /k aPh.3.s the dimension of length or height and is thus designated the gas-phase height of one transfer unit, The integral is dimensionless and indicates how many of these transfer units it takes to make up the whole tower. Consequently, it is called the number of gas-phase transfer units, N. Equation 40 may therefore be written as... 

Hq and aie called the overall gas-phase height of a transfer unit and the number of overall gas-phase transfer units, respectively. In the case of a straight equiUbrium line, is often neady concentration-independent as explained earher. In such cases, use of equation 47 is especially convenient... 

Combining these two mechanisms for gas-phase transfer, as done in equation 28, yields... 

NTU (Number of Transfer Units) The NTU required for a given separation is closely related to the number of theoretical stages or plates required to cariy out the same separation in a stagewise or plate-type apparatus. For equimolal counterdiffusion, such as in a binary distillatiou, the number of overall gas-phase transfer units Nqg required for changing the composition of the vapor stream from yi to yo is... 

The gas-phase rate coefficient fcc is not affecded by the fact that a chemic reaction is taking place in the liquid phase. If the liquid-phase chemical reaction is extremely fast and irreversible, the rate of absorption may be governed completely by the resistance to diffusion in the gas phase. In this case the absorption rate may be estimated by knowing only the gas-phase rate coefficient fcc of else the height of one gas-phase transfer unit Hq =... 

G, , and L,n for the particular conditions under investigation. Gas-phase transfer units are obtained from Eq. (14-134)... 

He = height of a gas-phase transfer unit, m Hi = height of a Rqiiid-phase transfer unit, m X = rii/ LmlGm) = slope of equilibrium hne/slope of operating hne... 

Tg = gas temperature Te. = hqiiid temperature Ti = interface temperature Hg = height of a gas-phase transfer unit G = weight gas rlow/area Cp = specific heat p = density... 

HETP = height equivalent to a theoretical plate, inches Hog = height of an overall gas phase transfer unit, inches... 

Height of gas phase transfer unit, ft or in. Enthalpy of the main air stream, Btu/Ib Liquid height over orifice, in. liquid Enthalpy of saturated air film at bulk water temperature, Btu/lb... 

Pressure is similar to temperature as a rate limiting factor since the diffusibility of a gas is inversely related to its pressure. For instance, loweringthe pressure 760 Torr(l atm)to 1 Torr increases the gas-phase transfer of reactants to the deposition surface and the... 

The number of overall gas-phase transfer units is often more conveniently expressed in terms of the partial pressure of the solute gas. 

Nuclides, reaction with monomers, 14 248 NuDat database, 21 314 Nukiyama-Tanasawa function, 23 185 Null-background techniques, in infrared spectroscopy, 23 139-140 Number-average molecular weight, 20 101 of polymers, 11 195, 196 Number density, of droplets, 23 187 Number of gas-phase transfer units (Nq), packed column absorbers, 1 51 Number of overall gas-phase transfer units (Nog), packed column absorbers, 1 52 Number of transfer units (Nt, NTU), 10 761... 

Figure 12.21. Nomograph for the estimation of the height of a gas-phase transfer unih54)...

K g Overall gas-phase transfer coefficient in terms of mole fractions kmol/m2s nl-2t- ... 

Ka can be defined as a gas-phase transfer coefficient, independent of the liquid layer, when the boundary concentration of the gas is fixed and independent of the average gas-phase concentration. In this case, the average and local gas-phase mass-transfer coefficients for such gases as sulfur dioxide, nitrogen dioxide, and ozone can be estimated from theoretical and experimental data for deposition of diffusion-range particles. This is done by extending the theory of particle diffusion in a boundary layer to the case in which the dimensionless Schmidt number, v/D, approaches 1 v is the kinematic viscosity of the gas, and D is the molecular diffusivity of the pollutant). Bell s results in a tubular bifurcation model predict that the transfer coefficient depends directly on the... 

For interfacial systems, potential functions should ideally be transferrable from the gas-phase to the condensed phase. Aqueous-mineral interfaces are not in the gas phase (although they may be close, see (7)), but both the water molecules and the atoms/ions in the substrate are in contact with an environment that is very different from their bulk environment. The easiest different environment to test, especially when comparing with electronic structure calculations, is a vacuum, so there is likely to be a great deal of information available on either the surface of the solid or the gas-phase polynuclear ion or the gas-phase aquo complex (i.e., Fe(H20)63+, C03(H20)62-). The gas-phase transfer-ability requirements on potential functions are challenging, but it is difficult to imagine constructing effective potential functions for such systems without using gas-phase systems in the construction process. This means that any water molecules used on these complexes must also transfer from the gas phase to the condensed phase. A fundamental aspect of this transferability is polarization. 

The first term under the integral can be recognized as the HTU term (here HG) the second term under the integral defines the number of individual gas-phase transfer units, Nq, required for changing the composition of the vapour stream from y2 to y2 ... 

The phenyl cation has been the subject of high-level ab initio calculations.116 The ground state was shown to be a singlet, and the singlet-triplet gap was estimated.116 The gas-phase transfers of H+, H-, and H2O to Ph+ have been studied.117 Arenium... 

Dvm Volume mean diameter m ft Hg Height of a gas phase transfer unit m ft... 

There are two key variables that are difficult to calculate NG and NL (gas phase transfer units and liquid phase transfer units, respectively). The number of transfer units for each phase is calculated in terms of contact time and vapor rate. The contact times are determined... 

Step 2. Next the number of gas phase transfer units NG is to be calculated. First froth height in inches HF must be calculated. If the dry tray pressure drop is 0.5 in or more, then use Eq. (3.37). 

Here Nq is dimensionless and is called the number of gas-phase transfer units Hq has the dimension of length or height and is referred to as the height of a gas-phase transfer unit. As shown in Eq. (16a), the required height of the packed bed hj is the product of Hq and Nq. 

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