Condensation binary vapor mixture

Fujii, T., and Shinzato, K., Various Formulas and Their Accuracy Concerning Heat and Mass Transfer in the Vapor Boundary Layer in the Case of Laminar Film Condensation of Binary Vapor Mixtures, Int. J. Heat Mass Transfer, Vol. 36, No. 1, pp27-33, 1993. 

Evolution of reflectivity signals over time has been used to temporally resolve the constituents of a binary vapor mixture [102]. Since the studied solvents (ethanol and acetone) have identical refractive indices, changes in the optical reflectance of porous silicon exposed to these vapors were shown to depend upon the rates of diffusion and adsorption of these species into the material. Time-resolved refrac-tometry revealed that an equimolar mixture of acetone and ethanol vapors exhibited markedly different condensation within porous silicon than did the pure mixture constituents (figure 16.14). This method is comparable to gas chromatography in that the vapor mixture interacts with the matrix in a manner dependent upon the physical properties of its components, but the porous silicon device... 

Nonequilibrium, or film, methods provide physically realistic formulations of the problem that yield more accurate local coefficients at the expense of complexity. Colburn and Hougen [77] developed a trial-and-error solution procedure for condensation of a single vapor mixed with a noncondensable gas. Colburn and Drew [203] extended the method to include condensation of binary vapor mixtures (with no noncondensables). Price and Bell [204] showed how to use the Colburn and Drew [203] method in computer-assisted design. 

As mentioned in Section IX-2A, binary systems are more complicated since the composition of the nuclei differ from that of the bulk. In the case of sulfuric acid and water vapor mixtures only some 10 ° molecules of sulfuric acid are needed for water oplet nucleation that may occur at less than 100% relative humidity [38]. A rather different effect is that of passivation of water nuclei by long-chain alcohols [66] (which would inhibit condensation note Section IV-6). A recent theoretical treatment by Bar-Ziv and Safran [67] of the effect of surface active monolayers, such as alcohols, on surface nucleation of ice shows the link between the inhibition of subcooling (enhanced nucleation) and the strength of the interaction between the monolayer and water. 

Propanol(l) and water vapor(2) are condensing on the cooled surface of a vertical tube. Nitrogen (3) is also present in the vapor mixture fed to the condenser. At the temperature and pressure in the condenser the diffusion coefficients of the three binary gas pairs are... 

Figure 9.4 shows another phase diagram at constant pressure. The x-axis shows the vapor-liquid mole fraction of the binary mixture. The y-axis shows temperature. The dew point line shows the temperature at which a superheated vapor mixture will begin to condense when cooled for all compositions of the mixture. The bubble point line shows the temperature at which a subcooled mixture will first begin to... 

Consider now the flow of a binary gas/vapor mixture in a heat exchanger with regard to condensation and coagulation. The relevant system of equations is similar to Eqs. (16.135). The main difference lies in the constancy of the tube cross-section, i.e. S = 1. Thus, we have ... 

Figure 1.3 shows a schematic of the batch distillation process for the separation of a volatile compound from a binary liquid mixture. It is heated in the bottom still to generate vapors, which condense at the top to yield distillate having a higher concentration of a the volatile compound. A part of the distillate is withdrawn as product while the rest is recycled to the still. An optimal control problem is to maximize the production of distillate of a desired purity over a fixed time duration by controlling the distillate production rate with time (Converse and Gross, 1963). 

Many systems, particularly mixtures of nonpolar organics and polar compounds such as water, will form two liquid phases and one vapor phase. A binary exanple, n-butanol and water, is discussed later (see Figure 8-2 and Problem 8.D3b In this section we consider calculations for multiconponent liquid-liquid-vapor systems. For exanple, if a vapor mixture of gasoline and water is partially condensed, the result will be an aqueous layer with a high mole fraction of water, an organic phase containing very litde water, and a vapor phase. The different conponents of gasoline will distribute between the three phases differendy. 

D5. We have a feed that is a binary mixture of methanol and water (55.0 mol% methanol) that is sent to a system of two flash drums hooked together. The vapor from the first drum is cooled, which partially condenses the vapor, and then is fed to the second flash drum Both drums operate at a pressure of 1.0 atm and are adiabatic. The feed rate to the first drum is 1000 kmol/h. We desire a liquid product from the first drum that is 30.0 mol% methanol (x = 0.30). The second drum... 

With reference to Fig. 6.11, assume that this binary feed mixture enters the column as saturated vapor on the fourth plate. Ideally, the liquid on the plate above the feed inlet (point L5) has the same composition as the feed, but is at a lower temperature since the latter is at the bubble-point temperature rather than at the dew-point temperature. Within the column, vapor flows upward through the liquid layer on each plate, while the liquid flows across each plate and down to the next plate by means of a downcomer. The vapor transfers heat to the liquid on each plate as it bubbles through the liquid. This heat transfer results in the evaporation of a small amount of the more volatile component from the liquid layer and correspondingly in the condensation of a small amount of the less volatile component in the vapor. Thus, the vapor becomes richer in nitrogen as the vapor comes in contact with the liquid layer and the liquid layer becomes richer in oxygen as the liquid contacts the vapor and flows downward from plate to plate. This is illustrated in Fig. 6.12, which shows the ideal temperature-composition of the vapor and liquid above and below the feed entry. As the saturated liquid moves down the column, its composition moves to the left along the bubble-point curve (points L4, L3,... 

To illustrate calculations for a binary system containing a supercritical, condensable component. Figure 12 shows isobaric equilibria for ethane-n-heptane. Using the virial equation for vapor-phase fugacity coefficients, and the UNIQUAC equation for liquid-phase activity coefficients, calculated results give an excellent representation of the data of Kay (1938). In this case,the total pressure is not large and therefore, the mixture is at all times remote from critical conditions. For this binary system, the particular method of calculation used here would not be successful at appreciably higher pressures. 

In the first class, azeotropic distillation, the extraneous mass-separating agent is relatively volatile and is known as an entrainer. This entrainer forms either a low-boiling binary azeotrope with one of the keys or, more often, a ternary azeotrope containing both keys. The latter kind of operation is feasible only if condensation of the overhead vapor results in two liquid phases, one of which contains the bulk of one of the key components and the other contains the bulk of the entrainer. A t3q)ical scheme is shown in Fig. 3.10. The mixture (A -I- B) is fed to the column, and relatively pure A is taken from the column bottoms. A ternary azeotrope distilled overhead is condensed and separated into two liquid layers in the decanter. One layer contains a mixture of A -I- entrainer which is returned as reflux. The other layer contains relatively pure B. If the B layer contains a significant amount of entrainer, then this layer may need to be fed to an additional column to separate and recycle the entrainer and produce pure B. 

Kellenbenz, J., and Hahne, E., Condensation of Pure Vapors and Binary Mixtures in Forced Flow, Inti. J. Heat Mass Transfer, Vol. 37, No.8, pp1269-1276, 1994. 

In Section A.l, the general laws of thermodynamics are stated. The results of statistical mechanics of ideal gases are summarized in Section A.2. Chemical equilibrium conditions for phase transitions and for reactions in gases (real and ideal) and in condensed phases (real and ideal) are derived in Section A.3, where methods for computing equilibrium compositions are indicated. In Section A.4 heats of reaction are defined, methods for obtaining heats of reaction are outlined, and adiabatic flame-temperature calculations are discussed. In the final section (Section A.5), which is concerned with condensed phases, the phase rule is derived, dependences of the vapor pressure and of the boiling point on composition in binary mixtures are analyzed, and properties related to osmotic pressure are discussed. 

Let us consider vapor-liquid (or vapor-solid) equilibria for binary mixtures. For the sake of simplicity it will be assumed that all gases are ideal. In addition to the vapors of each component of the condensed phase, the gas will be assumed to contain a completely insoluble constituent, the partial pressure p of which may be adjusted so that the total pressure of the system, p, assumes a prescribed value. Therefore, C = 3, P = 2, and, according to equation (51), F = 3. Let us study the dependence of the equilibrium vapor pressures of the two soluble species p and P2 on their respective mass fractions in the condensed phase X and X2 at constant temperature and at constant total pressure. Since it is thus agreed that T and p are fixed, only one remaining variable [say X ( = l — "2)] is at our disposal p, P2 and the total vapor pressure p = p + p2 will depend only on X. ... 

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