Air-water vapors

Free from NH3 and CO2 total pressure of air + water vapor is 760 mm,... 

For systems other than air—water vapor or for total system pressures different from 101.3 kPa (1 atm), humidity diagrams can be constmcted if basic phase-equihbria data are available. The simplest of these relations is Raoult s law, apphcable at small solute concentrations ... 

In Figure 2 the lines, volume, m /kg dry air, indicate humid volume, which includes the volume of 1.0 kg of dry gas plus the volume of vapor it carries. Enthalpy at saturation data are accurate only at the saturation temperature and humidity however, for air—water vapor mixtures, the diagonal wet bulb temperature lines are approximately the same as constant-enthalpy adiabatic cooling lines. The latter are based on the relationship ... 

At any given relative humidity, x is constant. In a typical siHca gel—air—water vapor system at 5—50°C, pjp = 1.79 x), where... 

Psychrometry is concerned with determination of the properties of gas-vapor mixtures. The air-water vapor system is by far the system most commonly encountered. 

For systems other than air-water vapor, the value of h /k c, may differ appreciably from unity, and the wet-bulb and adiabatic-saturation temperatures are no longer equal. For these systems the psychrometric ratio may be obtained by determining h /k from heat- and mass-transfer an ogies such as the Chilton-Colburn analogy [Ind. Eng. Chem., 26, 1183 (1934)]. For low humidities this analogy gives... 

FIG. 12-4 Humidity chart for air-water vapor mixtures. To convert British thermal units per pound to joules per Idlo-gram, multiply by 2326 to convert British thermal units per pound dry air-degree Fahrenheit to joules per Idlogram-kelvin, multiply hy 4186.8 and to convert cubic feet per pound to cubic meters per kilogram, multiply by 0.0624. 

From air-water vapor-mixture tables, the enthalpy hi of the ambient air at 78 F wet-bulb temperature is 41.58 Btu/lb. 

For air-water-vapor mixtures, it so happens that h /k = C, approximately, although there is no theoretical reason for this. Hence, since the ratio — H )/(f , — t) equals h /k /X, which represents the slope of the wet-bulb-temperature lines, it is also equal to C, /X, the slope of the adiabatic-saturation lines as shown previously. 

A given humidity chart is precise only at the pressure for which it is evaluated. Most air-water-vapor charts are based on a pressure of 1 atm. Humidities read from these charts for given values of wet- and diy-bulb temperature apply only at an atmospheric pressure of 760 mmHg. If the total pressure is different from 760 mmHg, the humidity at a given wet-bulb and dry-bulb temperature must be corrected according to the following relationship. 

Figures 12-37 to 12-39 show humidity charts for carbon tetrachloride, oenzene, and toluene. The lines on these charts have been calculated in the manner outlined for air-water vapor except for the wet-bulb-temperature lines. The determination of these hnes depends on data for the psychrometric ratio /j Z/c, as indicated by Eq. (12-22). For the charts shown, the wet-bulb-temperature hnes are based on the following equation ...

A rate balance between evaporation and heat transfer when radiation occurs may be modified by means of the psychrometric ratio for air-water vapor mixtures to give ... 

Psychrometric charts plot wet bulb and dry bulb data for air-water vapor mixtures at atmospheric pressure. These charts are quite useful for... 

Computes properties of air-water vapor mixtures for HVAC, combustion, aerodynamic, and meteorological applications. Any two independent properties may be inpuicd by... 

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)... 

Example No. 6-3 Actual Air Capacity For Air-Water Vapor Mixture... 

For saturated air-water vapor systems. Figures 6-20A, B, C, and D are useful in solving for the pounds of water vapor per pound of air (Dalton s Law, Equation 6-2). 

An air-water vapor mixture is saturated with water vapor at 80°F and 2 in. Hg abs total pressure. The air in the mixture is 60 Ibs/hr. Determine the volume at these conditions. 

Psychrometry has to do with the properties of the air-water vapor mixtures found in the atmosphere. Psychrometry tables, published by the US Weather Bureau, give detailed data about vapor pressure, relative humidity and dew point at the sea-level barometer of 30 in Hg, and at certain other barometric pressures. These tables are based on relative readings of dry bulb and wet bulb atmospheric temperatures as determined simultaneously by a sling psychrometer. The dry bulb reads ambient temperature while the wet bulb reads a lower temperature influenced by evaporation from a wetted wick surrounding the bulb of a parallel thermometer. 

Air/water vapor mixture, chart, 364,365 Air/water vapor, 359 Capacity at ejector suction, 369 Capacity for process vapor, 362 Evacuation time, 371, 380 Load for steam surface condenser, 367 Non-condensables, 362, 363 Size selection, 371 Steam pressure factor, 373 Steam requirements, 372 Steain/air mixture temperature, 361 Total weight saturated mixture, 362 Capacity, 358 Discharge, pressure, 358 Effect of excess steam pressure, 358 Effects of back pressure, 359 Effects of wet steam, 356 Inter-and-after condenser, 351 Load variation, 370 Materials of construction, 347 Molecular weight entrainment, chart, 360 Performance, 358, 370, 375 Relative comparison, 357... 

The pressure of the water vapor in the air/water vapor mixture must not exceed 23 % of the total pressure of the mixture. 

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