Vaporization, partial enthalpy

Fig. 9. Vapor-phase enthalpy of anhydrous HF where the numbers represent the partial pressure of HF in kPa (1,17,20,31,33). The critical point occurs at 188°C. To convert kPa to psi, multiply by 0.145. To convert kJ/kg to Btu/lb, multiply by 4.302 x 10 . ...

A tabulation of the partial pressures of sulfuric acid, water, and sulfur trioxide for sulfuric acid solutions can be found in Reference 80 from data reported in Reference 81. Figure 13 is a plot of total vapor pressure for 0—100% H2SO4 vs temperature. References 81 and 82 present thermodynamic modeling studies for vapor-phase chemical equilibrium and liquid-phase enthalpy concentration behavior for the sulfuric acid—water system. Vapor pressure, enthalpy, and dew poiat data are iacluded. An excellent study of vapor—liquid equilibrium data are available (79). 

Temperature rc) Humidity kg HjO/kg dry air) Water vapor partial pressure (kPa) Water v K>r partial density (kg/m ) Water vaporization heat M/kg) Mixture enthalpy (kj/kg dry air) Dry air partial density (lKinematic viscosity (I0< mJ/s) Specific heat (kJ/K kg) Heat conductivity (W/m K) Diffusion factor water air (1 O mJ/s) Temperature rc)... 

For the temperature dependency of Pu(g), Battles et al. (15) combined the partial pressure of Pu(g) determined at 2219 K and an assumed partial enthalpy of vaporization value of 118 kcal/mol, leading to the expression... 

Parametric studies, polymer growth. 237-39 Partial enthalpy of vaporization,... 

The heat conduction flux is given by — fc dT/dz aed for ideal vapors partial molar enthalpies (/f.) depend only on temperature. Substitution and integration result in an expression for the ratio of Ihe heat transfer coefficient with and without mass transfer ... 

It is required to design a fractionation tower to operate at 101.3 kPa to obtain a distillate consisting of 95 mole% acetone (A) and 5 mole% water, and a residue containing 1 mole% A. The feed liquid is at 125°C and 687 kPa and contains 57 mole% A. The feed is introduced to the column through an expansion valve so that it enters the column partially vaporized at 60°C. Construct an H-x-y diagram and determine the molar ratio of liquid to vapor in the partially vaporized feed. Enthalpy and equilibrium data are as follows. 

Measurements of the saturated vapor pressures of plasticizers over plasticized cellulose nitrate were used for calculation of chemical potentials of plasticizers and partial enthalpies and entropies of mixing. ... 

The temperature dependence of the volatility rate is included in the Fsi(OH)4 and arises from the enthalpy for reaction of Eq. (7-20). Also, it can be seen from Eq. (7-20) that the partial pressure of Si(OH)4 increases with the square of the water vapor partial pressure. This pressure dependence has been demonstrated by Hashimoto (1992) for silica. Inserting this relationship in Eq. (7-23), while remembering that in combustion environments the water vapor partial pressure scales with the total pressure, results in ... 

Some components will be in the vapor phase when their properties as a pure material indicate they should be liquid. Other components will be in the liquid phase at temperatures above their critical temperatures. Clearly, partial enthalpies should be employed to produce accurate results. A significant amount of work has been done in developing correlations for calculating partial enthalpies... 

DGA Partial derivative of the enthalpy balance equation (7-14) with respect to the vapor-feed ratio. 

FIG. 2-29 Enthalpy-concentration diagram for aqueous sodium hydroxide at 1 atm. Reference states enthalpy of liquid water at 32 F and vapor pressure is zero partial molal enthalpy of infinitely dilute NaOH solution at 64 F and 1 atm is zero. [McCahe, Trans. Am. Inst. Chem. Eng., 31, 129(1935).]... 

The desired enthalpy of formation of 6,6-dimethylfulvene was determined by Roth citing measurement of hydrogenation enthalpies, and chronicled by Pedley citing enthalpies of combustion and vaporization. The two results differ by 7 kJ mol-1. We have opted for Roth s value because it is in better agreement with a value calculated using Roth s force field method. It is also to be noted that measurement cited by Pedley for the neat condensed phase could be flawed by the presence of partially polymerized fulvene and neither elemental abundance of the compound nor analysis of the combustion products would have disclosed this. Likewise, the measured enthalpy of vaporization would not have necessarily uncovered this contaminant. 

The term JT A Hi in equations 8.1 and 8.3 is frequently very small compared to the uncertainty in the determination of A/frcp and in many instances can safely be neglected. This should of course be tested by performing blank experiments under normal operating conditions. For example, the enthalpy associated with breaking an ampule (independently from the contribution from vaporization effects) can be determined by breaking ampules partially filled with the calorimetric solvent in the calorimetric solvent. For many systems this contribution is negligible, provided that a well-designed breaker mechanism and ampules ensure that the dissipation of heat is reduced to a minimum. The importance of vaporization effects can be evaluated as described by Vanderzee [129]. 

Chloroethene (vinyl chloride) is a gas at the temperature considered. Hence, the enthalpy of solution (Awa//,) is given by the sum of the enthalpy of condensation (AcmiHi, which is equal to the negative enthalpy of vaporization) and the excess enthalpy in aqueous solution (Hi) (Fig. 5.1 and Eq. 5-26). Horvath et al. (1982) gives the solubilities of chloroethene at 0°C, 25°C, and 50°C and 1 bar partial pressure. Also given are the vapor pressures of the superheated liquid at these three temperatures. 

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