Air-water mixture

Hewitt, G. F., King, I. and Lovegrove, P. C. Brit. Chem. Eng. 8 (1963) 311-318. Holdup and pressure drop measurements in the two phase annular flow of air-water mixtures. 

Heywood, N. I. and Richardson, J. F. Chem. Eng. Sci. 34 (1979) 17-30. Slug flow of air-water mixtures in a horizontal pipe determination of liquid holdup by y-ray absorption. 

Govier, G. W Radford. B. A. and Dunn, J. S. C Canatl. J. Chem. Eng. 55 (1957) 58, The upwards vertical flow of air-water mixtures I. Effect Of air and water rates on flow pattern, hold-up and pressure drop. 

Figure 3.64 Measured and calculated pressure wave propagation velocity in air-water mixtures at 25 psia. (From Henry et al., 1969. Copyright 1969 by Plenum Publishing, New York. Reprinted with permission.)... 

Quandt (1962) measured the values of (CfICm - 1) at various axial positions of an air-water mixture flow in a 0.25-in. X 3-in. channel and converted the raw data to the exchange mass flux, pLV(, as shown in Figure 5-23. He also measured the film velocity Vf by injecting a pulse of dye into the liquid film and recording its transport time between two photocells. Such measured data are shown in Figure 5.24. By using the measured values for Vf, the liquid film thickness t may be calculated as... 

Visual deflnitions of flow patterns in vertical flow appear to cause more diflBculty than do those in horizontal flow. As the gas rate increases at a constant liquid rate, a dispersed type of flow will be reached at lower gas velocities in a vertical tube than in a horizontal one because of the influence of gravity in causing back flow of liquid. Also, vertical flow patterns tend toward radial symmetry, which is not the case in horizontal flow. A classification of vertical flow patterns based largely on air-water mixtures is given below. Surprisingly little work has been carried out for the vertical upward flow of components other than these, or steam-water mixtures. 

Here Va and are the true velocities at the entrance, of gas and liquid, respectively, and do is the critical droplet diameter. The value of the Wee depends on the degree of shock at the entrance section e.g., for smooth liquid injection, 22 was used, and for tee entrances, 13 to 16. Collier and Hewitt (C6) also measured entrainment in air-water mixtures, and have extended the same correlation to much wider ranges, using We — 13 in the case of jet injection with the results shown in Fig. 9. Anderson et al. (A5), during mass-transfer studies in a water-air-ammonia system, found en-... 

Partial Pressure. For an air-water void, it is assumed that the void initially contains dry air only. In the case of an air-water mixture in the void, the mole fraction of dry air is... 

The interface concentration is called 6 sat> even though an air-water mixture may not be saturated. 

In a countercurrent flow of liquid and gas in a vertical tube, at a critical gas velocity, vG, a situation arrises at which the liquid supply to the tube is interrupted and the liquid film inside the wall is held at rest see sketch, Fig. 45. Increasing the gas velocity above vG causes the film attachment point to rise in the tube. Lowering gas velocity below vG causes the liquid film to move down the tube. Most of the researchers reported little or no difference between these two critical vG values. However, Wallis and Makkenchery [69] stated that, for small tube diameters (D = 6 mm) and air-water mixtures, the velocities differed by a factor of about two. These researchers found that the lower critical vG increased with pipe diameter, D, and was independent of it for large values of D. For acrylic glass the final result was found to be ... 

An important conclusion from Fig. 6 is that for a small void, it is immaterial wheter or not the initial void contains pure water or an air/water mixture. The diameters at any particular time during the cure cycle are nearly identical when the initial void diameters under 0.1 atm are the same. An air/water void initially containing pure air has a very large driving force for diffusion of water vapor from the resin to the void during the first few minutes of the cycle. This results in diffusion into the void of a large amount of water vapor (relative to the original amount of dry air in the void). Consequently the mole fraction of water vapor in the air/water void quickly approaches unity, and thereafter the rate of diffusion of water vapor across the interface of the air/water void is nearly the same as that for a pure water void. 

Before solving the equations, we need system property data, which, in this case, are thermodynamic properties. Equations 3.2.9 and 3.2.11 states that we may obtain vapor pressures for water from steam tables, such as those compiled by Chaar et al. [13]. Equation 3.2.10 also states that we can find the enthalpy of vaporization in the steam tables. We assume that the air-water mixture is ideal to calculate the enthalpy of air, so we can use the mole-fraction average of the pure-component enthalpies. Equations 3.2.12 and 3.2.13 in Table 3.2.1 give the mole fraction average of the inlet and outlet enthalpy. Table 3.2.1 also lists pure component enthalpies for water vapor (Equations 3.2.14 and 3.2.16) and for air (Equa-... 

Similar results were found by Bozo [44]. Palladium deposited onto ceria-zirconia Ceo67Zro3302 solid solution showed very high activity in methane combustion (T50 close to 300 C) but similar to that of palladium deposited onto alumina. Like for the case of platinum a deactivation is observed during tests at temperatures comprised between 200°C and 400 C (Fig. 13.3). However when aged at 1000 C under an air+water mixture this catalysts showed superior resistance compared to classical catalysts as far as activity is considered. Despite a severe sintering of both metal (dispersion is now 1%) and support, whose surface area is close to 4 mVg, T50 was shifted to 420 C, i.e. 120°C only, still much lower for platinum deposited on the same support which showed a TSO close to 620°C. Calculation of specific activities in the 200-300°C range have clearly evidenced that ceria-zirconia support does not have any influence upon performance of PdO in... 

Only one independent balance can be written for the splitting point because the streams entering and leaving this subsystem are labeled as having identical compositions, so that the dry air/water mixture in all three streams behaves like a single species. (Convince yourself write a total mole balance and a dry air or water balance around the splitting point and observe that you gel the same equation each time.)... 

Coteman and Garimella [1] investigated the effect of tube diameter and shape on flow patterns and flow regime transitions for air-water mixture flow in tubes with small hydraulic diameters (1.3 mm to 5.5 mm). Gas... 

Govier, G. W., and Omer, M. M. (1962) The Horizontal Pipeline Flow of Air-Water Mixtures, Canadian Journal of Chemical Engineering, pp. 93-104. 

The adiabatic cooling lines are lines of almost constant enthalpy for the entering air-water mixture, and you can use them as such without much error (1 or 2%). However, if you want to correct a saturated enthalpy value for the deviation which exists for a less-than-saturated air-water vapor mixture, you can employ the enthalpy deviation lines which appear on the chart and which can be used as illustrated in the examples below. Any process that is not a wet-bulb process or an adiabatic process with recirculated water can be treated by the usual material and energy balances, taking the basic data for the calculation from the humidity charts. If there is any increase or decrease in the moisture content of the air in a psychrometric process, the small enthalpy effect of the moisture added to the air or lost by the air may be included in the energy balance for the process to make it more exact as illustrated in Examples 4.47 and 4.49. 

Simple FORTRAN programs have been prepared for the reader s use that solve linear and nonlinear equations, retrieve the properties of water and steam, and of air-water mixtures, calculate the vapor pressure of pure substances, calculate enthalpy changes from heat capacity equations, and so on. A disk containing these codes will be found in a pocket in the back of the book. (Readers are encouraged to use library codes when available, codes that may be more accurate and robust than the simple codes provided.) As a result, the portions of the book formerly treating... 

If a stream of air is intimately mixed with a quantity of water in an adiabatic system, the temperature of the air will drop and its humidity will increase. If the equilibration time or the number of transfer units approaches infinity, the air-water mixture will reach saturation. The acUabatic saturation temperature T is given by a heat balance between the initial unsaturated vapor-gas mixture and the final saturated mixture at thermal equilibrium ... 

Example 7 Determination of Moist Air Properties An air-water mixture is found from the heat and mass balance to he at 60 C (333 K) and 0.025 kg/kg (25 g/kg) absolute humidity. Calculate the other main parameters for the mixture. Take atmospheric pressure as 101,325 Pa. 

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