Gas-side coefficient

T. Single liquid drops in gas, gas side coefficient =2 + ANiS,Ni [E] Used for spray drying (arithmetic partial pressure difference). [88] p. 489... 

The combustion gases flow across the tube banks in the convection section and the correlations for cross-flow in tube banks can be used to estimate the heat transfer coefficient. The gas side coefficient will be low, and where extended surfaces are used an allowance must be made for the fin efficiency. Procedures are given in the tube vendors literature, and in handbooks, see Section 12.14, and Bergman (1978b). 

In developing our major design expression (Equation 5.33), it was assumed that the overall mass transfer coefficient and the gas side coefficient were the... 

U. Single liquid drops in gas, gas side coefficient ksMsdrP =2 + ANt3sN s% A = 0.552 or 0.60. xt dpPf,vs Ly,Re.g — Pg [E] Used for spray drying (arithmetic partial pressure difference). vs = slip velocity between drop and gas stream. Sometimes written with MgP/pg = RT. [90] p. 388 [121]... 

The purpose of most gas dispersion processes is to transfer gas into the liquid, sometimes to obtain a chemical reaction. The mass transfer rate across the gas-liquid interface can thus be the rate limiting step in the process, especially when the chemical reaction is fast. The rate of mass transfer is generally described by the mass transfer coefficients ki and kg, which are the coefficients for the liquid and the gas side, respectively. Usually, the gas side coefficient is neglected because the resistance to mass transfer on the liquid side is generally much higher than on the gas side. 

Air-cooled two fins/cm of tnbe length nse finned tnbes on gas side to give less weight, less pressnre drop, bnt not for dirty gases on the fin side because of difficulty in cleaning. Use when the potential hnned side coefficient is small (0.05 to 0.1 kW/m °C) and when the ratio of tnbe side to gas side coefficient is 75 to 300, bnt not when it is 1 to 25. Use hfi , not area only, for optimization (becanse heat transfer coefficient decreases as the hn area increases). Finned tnbes with 15 to 20 nF total area/m bare tnbe area, 0.4 to 0.6 kW/m °C of bare tnbe approach temperatnre >26°C fan power is 5 to 13 kW/kW thermal energy transferred or 0.15 kW/m of bare tnbe. 

The value of the saturation concentration,, is the spatial average of the value determined from a clean water performance test and is not corrected for gas-side oxygen depletion therefore K ji is an apparent value because it is determined on the basis of an uncorrected. A tme volumetric mass transfer coefficient can be evaluated by correcting for the gas-side oxygen depletion. However, for design purposes, can be estimated from the surface saturation concentration and effective saturation depth by... 

Danckwerts and Gillham did not investigate the influence of the gas-phase resistance in their study (for some processes gas-phase resistance may be neglected). However, in 1975 Danckwerts and Alper [Trans. Tn.st. Chem. Eng., 53, 34 (1975)] showed that by placing a stirrer in the gas space of the stirred-cell laboratoiy absorber, the gas-phase mass-transfer coefficient fcc in the laboratoiy unit could be made identical to that in a packed-tower absorber. When this was done, laboratoiy data obtained for chemically reacting systems having a significant gas-side resistance coiild successfully be sc ed up to predict the performance of a commercial packed-tower absorber. 

Liquid-Film Coefficients (Physical) and (Reactive) The gas-side resistance can be eliminated by employing a pure gas, thus leaving the liquid film as the only resistance. Alternatively, after the gas-film resistance has been found experimentally or from corre-... 

Calculate the shell-side dry-gas film coefficient, hg or h, for outside tube conditions. Assume a baffle spacing or about equal to one shell diameter. Use the shell-side method described in Equation 10-48 and Figure 10-54. This is necessary for inlet conditions and then must be checked and recalculated if sufficient change occurs in the mass flow rate, G, to yield a change in hg. 

In the convective section, the gas-side heat transfer coefficient controls the heat flux distribution since the... 

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. ... 

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. 

SAHAY, B. N. and SHARMA, M. M. Chem.Eng. Sci. 28 (1973) 41. Effective interfacial areas and liquid and gas side mass transfer coefficients in a packed column. 

The gas film coefficient is dependent on turbulence in the boundary layer over the water body. Table 4.1 provides Schmidt and Prandtl numbers for air and water. In water, Schmidt and Prandtl numbers on the order of 1,000 and 10, respectively, results in the entire concentration boundary layer being inside of the laminar sublayer of the momentum boundary layer. In air, both the Schmidt and Prandtl numbers are on the order of 1. This means that the analogy between momentum, heat, and mass transport is more precise for air than for water, and the techniques apphed to determine momentum transport away from an interface may be more applicable to heat and mass transport in air than they are to the liquid side of the interface. 

We will conserve both nitrogen and oxygen gas. Often, argon is considered to be similar to nitrogen because both are nonreactive and have close to the same diffusion coefficient. Because both gases are volatile, there is no significant resistance on the gas side of the interface, and... 

The newer volatile anesthetics, desflurane and sevoflurane, have physicochemical characteristics (ie, low blood gas partition coefficients) that are favorable to a more rapid onset and shorter duration of anesthetic actions compared with isoflurane and halothane. However, both of these newer agents also have certain limitations. The low volatility of desflurane necessitates the use of a specialized heated vaporizer, and the pungency of the drug leads to a high incidence of coughing and sympathomimetic side effects that make it less than ideally suited for induction of anesthesia. 

In the case of gas-gas or liquid-liquid heat exchangers, the film coefficients for the fluids on both sides of the metal wall are of the same order of magnitude, and can be predicted by correlations, for example, with Equation 5.8a or 5.12a. Neither of the fluid film resistances can be neglected. In a gas-liquid heat exchanger, the controlling resistance is on the gas side, as mentioned before. 

The second section presents a review of studies concerning counter-currently and co-currently down-flow conditions in fixed bed gas-liquid-solid reactors operating at elevated pressures. The various consequences induced by the presence of elevated pressures are detailed for Trickle Bed Reactors (TBR). Hydrodynamic parameters including flow regimes, two-phase pressure drop and liquid hold-up are examined. The scarce mass transfer data such gas-liquid interfacial area, liquid-side and gas-side mass transfer coefficients are reported. 

Regrettably, for our knowledge there is a lack of information in the open literature on values of the gas-side mass-transfer coefficient, k( , in TBR operating at elevated pressures and especially on the effect of the gas density on it. 

The design of packed column reactors is very similar to the design of packed columns without reaction (Volume 2, Chapter 12). Usually plug flow is assumed for both gas and liquid phases. Because packed columns are used for fast chemical reactions, often the gas-side mass transfer resistance is significant and needs to be taken into account. The calculation starts on the liquid side of the gas-liquid interface where the chemical reaction rate constant is compounded with the liquid side mass transfer coefficient to give a reaction-enhanced liquid-film mass transfer... 

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