Humidification Flashcards
science behind the humification processes which refers mainly to the systematized knowledge of the properties of air and water
Psychrometry
- Its broader meaning includes the principles which govern the properties and behavior of mixtures of the so called “fixed” gases with condensable vapors.
Psychrometry
The mass of vapor carried by a unit mass of vapor-free gas
Saturation/Humidity
Saturation Equation
S= (M_a/M_b) * p_a/(P-p_a)
Where,
* PA – the partial pressure of the vapor in the mixture
* P - the total pressure (usually atmospheric unless otherwise specified)
* MA, MB – the molecular weights of components A and B, respectively
A gas in which the vapor is in equilibrium with the liquid at the gas temperature and pressure
Saturated Gas
—– temp, —– capacity to hold vapor
higher, higher
—– pressure, —- capacity for vapor
higher, lesser
in this condition, there would be higher tendency for vapor to condense
at this point the partial pressure of that vapor in the gas mixture is equal to the saturation pressure of that vapor at a particular pressure and temperature.
Saturated Gas
A gas in which the water vapor is in equilibrium with the liquid water at the gas temperature and pressure.
Saturated Air
- Ratio of the partial pressure of the vapor to the vapor pressure of the liquid at the gas temperature and pressure.
Relative Saturation, RS
Relative Saturation formula
%RS = (Pa/P*sat) x 100%
Saturated Gas Formula
Psat*=pa
Ratio of the actual saturation S (actual humidity, H) to the maximum saturation Smax (saturation humidity, HS) at the gas temperature and pressure.
Percentage Saturation
%S =
%S=S/S_max ×100%
=(pa/(P-pa ))/((Psat)/(P-Psat ))×100%
=%RS (P-Psat)/(P-pa )
- the temperature at which the vapor just starts to condense
Dew Point
- at this point, the partial pressure of the vapor is the vapor pressure.
Dew point
Dew Point Formula
ln(P_sat^* )=A-B/(C+T)
Dew pt for air-water system
ln〖P_sat^* (mmHg)〗=18.3036-3816.44/(T(K)-46.13)
- The total volume of a unit mass of vapor-free gas plus whatever vapor it may contain at 1 atm (or any specified pressure) and temperature.
Humid volume (vH)
υ_H
υ_H=(RT/P) (1/M_B +S/M_A )
B
gas
A
vapor
- The heat energy necessary to increase the temperature of a unit mass of gas plus whatever vapor it may contain by 1°C or 1°F.
Humid heat (Cs)
Humid Heat SI Formula
C_s=1.005+1.88H kJ/(kg dry air ∙K) (SI)
Humid heat AES Formula
C_s=0.24+0.45H BTU/(〖lb〗_m dry air ∙℉) (AES)
Total Enthalpy
H_y=C_(P,B) (T-T_0 )+Sλ_0+C_(P,A) S(T-T_0 )
or
H_y=C_s (T-T_0 )+Sλ_0
Total Enthalpy SI Formula
H_y=(1.005+1.88H)(T-T_0 )+2501.4H kJ/(kg dry air∙K) (SI)
- The temperature that would be attained if the gas were saturated in an adiabatic process.
Adiabatic Saturation Temperature (Ts)
- The steady-state temperature attained by a wet-bulb thermometer under standardized conditions.
Wet-Bulb Temperature (Tw)
- The actual gas (air) temperature as measured by a thermometer suitably shielded from radiation and moisture.
Dry-Bulb Temperature (T)
- The maximum temperature a particular gas will obtained.
Adiabatic Saturation Temperature (Ts)
- The steady-state nonequilibrium temperature reached when a small amount of water is contacted under adiabatic conditions by a continuous gas stream.
Wet Bulb Temperature
- This means that for air-water system, the adiabatic saturation lines and the psychrometric lines are identical for a psychrometric chart.
Lewis Relation
