Humidity Plus (Calculates Unknown Psychrometric Values)
Relative Humidity
Air (or empty space, or any other gas) has a given capacity to hold water vapour. This capacity, depends mainly on temperature.
In general, the hotter the air, the more water vapour it can hold. At any given temperature, air that contains its full capacity of water vapour, is said to be "saturated".
The "relative humidity" of the air expresses how fully saturated it is with water vapour.
A variety of other ("absolute") measures are used to express how much mass of water vapour is actually present (irrespective of temperature or level of saturation).
This program calculates the values of (see list below) in accordance with the functions, constants and polynomials defined in BS 1339 Part 1 (2002)
Other polynomials can be selected :
- Sonntag - Bogel (BSI) (ITS-90)
- Wexler - Greenspan (ITPS-68)
- Hardy - Hardy (ITS-90)
BS 1339 default constants can be selected or varied for the following :
- Universal gas constant (J/(kmol K))
- Molar mass of dry air (kg/kmol)
- Molar mass of water (kg/kmol)
- Psychrometer coefficient (select value or calculate according to BS 1339)
Variables determined :
- Dry Bulb Temperature
- Wet Bulb Temperature
- Relative Humidity (%rh)
- Dew Point Temperature
- Enthalpy (Reference 0°C)
- Mixing (Humidity) Ratio
- Humid (Specific) Volume
- Saturation Mixing Ratio
- Vapour (Partial) Pressure
- Parts per million by Weight
- Parts per million by Volume
- Volumetric (Absolute) Humidity
- Density of humid gas (air)
- Vapour Mole Fraction
- Vapour Mole Ratio
- Specific Humidity
- Dry gas (air) Mole Fraction
- Percent by Weight
- Percent by Volume
- Density of gas (air)
- Dry Bulb Vapour Pressure
- Dew Point Vapour Pressure
- Enhancement factor Tdb
- Enhancement factor Tdp
- Humid Heat
- Percentage Saturation
- Adiabatic Saturation Temperature
- Saturation Vapour Pressure @ Temperature of adiabatic saturation
- Psychrometer Coefficient
- Wet Bulb Vapour Pressure
Features
- Pressure units : Pa, kPa, MPa, mbar, m H²O, mm Hg, kgf/cm², atm, in H²O, in Hg, lbf/in², lbf/ft²
- Temperature units : °C, °F, K, °R
- Density units : kg/m³, g/m³, lb/ft³, gr/ft³
- Specific volume units : m³/kg, dm³/kg, ft³/lb, in³/lb
- Mixing ratio units : kg/kg, g/kg, lb/lb, gr/lb
- Specific energy units : kJ/kg, J/kg, Btu/lb, ft lbf/lb
- Altitude units : mm, cm, metre, km, inch, feet, mile
- Altitude calculated to ISA : ISO
- Results can be copied to the Clipboard
- Print results
