moistairtab

MoistAirTab™ Functions

The MoistAirTab add-in package is based on a set of 18 core functions that together calculate over 25 thermodynamic and transport properties of steam. You can use these functions directly in your spreadsheet or you can use MoistAirTab’s easy-to-use dialog boxes to automatically generate the appropriate function call with the correct arguments.

All of the MoistAirTab functions begin with the prefix MA. The MoistAirTab functions require as input two independent variables in addition to the total pressure. The first independent variable can be either: Dry bulb temperature (Tdb), Humidity Ratio (W), or Relative Humidity (RH). The second independent variable can be either: Dry-bulb Temperature (Tdb), Wet-bulb Temperature (Twb), Humidity Ratio (W), or Relative Humidity (RH), Enthalpy (H), Entropy (S), or Volume (V). These functions are summarized in Table 1 below.

MoistAirTab also includes functions for obtaining the barometric pressure and temperature as a function of altitude.

Table 1: MoistAirTab Worksheet Functions

Function	Calculates at Specified	Calling Sequence Example
Psychrometric Property Functions
MATDBTWB	Dry bulb temperature and Wet bulb temperature	MATDBTWB(dry bulb, wet bulb, property code, pressure, units)
MATDBRH	Dry bulb temperature and Relative humidity	MATDBRH(dry bulb, relative humidity, property code, pressure, units)
MATDBW	Dry bulb temperature and Humidity ratio	MATDBW(dry bulb, humidity ratio, code, pressure, units)
MATDBH	Dry bulb temperature and Enthalpy	MATDBH(dry bulb, enthalpy, property code, pressure, units)
MATDBS	Dry bulb temperature and Entropy	MATDBS(dry bulb, entropy, property code, pressure, units)
MATDBV	Dry bulb temperature and Volume	MATDBV(dry bulb, volume, property code, pressure, units)
MAWTWB	Humidity ratio and Wet bulb temperature	MAWTWB(humidity ratio, wet bulb, property code, pressure, units)
MAWTDB	Humidity ratio and Dry bulb temperature	MAWTDB(humidity ratio, dry bulb, property code, pressure, units)
MAWRH	Humidity ratio and Relative Humidity	MAWRH(humidity ratio, relative humidity, property code, pressure, units)
MAWH	Humidity ratio and Enthalpy	MAWH(humidity ratio, enthalpy, property code, pressure, units)
MAWS	Humidity ratio and Entropy	MAWS(humidity ratio, entropy, property code, pressure, units)
MAWV	Humidity ratio and Volume	MAWV(humidity ratio, volume, property code, pressure, units)
MARHTWB	Relative Humidity and Wet bulb temperature	MARHTWB(relative humidity, wet bulb, property code, pressure, units)
MARHTDB	Relative Humidity and Dry bulb temperature	MARHTDB(relative humidity, dry bulb, property code, pressure, units)
MARHW	Relative Humidity and Humidity ratio	MARHW(relative humidity, humidity ratio, property code, pressure, units)
MARHH	Relative Humidity and Enthalpy	MARHH(relative humidity, enthalpy, property code, pressure, units)
MARHS	Relative Humidity and Entropy	MARHS(relative humidity, entropy, property code, pressure, units)
MARHV	Relative Humidity and Volume	MARHV(relative humidity, volume, property code, pressure, units)
Constant Properties
MAMWW	Molecular weight of water	MAMWW(units)
MAMWA	Molecular weight of air	MAMWA(units)
MATMIN	Minimum dry bulb temp.	MATMIN(units)
MATMAX	Maximum dry bulb temp.	MATMAX(units)
MAPMIN	Minimum pressure	MAPMIN(units)
MAPMAX	Maximum pressure	MAPMAX(units)
MAPZ	Pressure at specified height	MAPZ(height, units)
MATZ	Temperature at specified height	MATZ(height, units)

The MoistAirTab functions return the requested property in either Metric/SI or English units. The thermodynamic properties and the units in which they are available is shown in the following table.

Table 2: MoistAirTab Thermodynamic Properties

Code	Property	Metric/SI Units	English Units
0	Dry bulb temperature	°C	°F
1	Wet bulb temperature	°C	°F
2	Dew point temperature	°C	°F
3	Pressure	bar	psia
4	Saturation water vapor pressure	bar	psia
5	Saturation pressure at wet bulb temperature	bar	psia
6	Saturation pressure at dew point pressure	bar	psia
7	Water mole fraction	dimensionless	dimensionless
8	Air mole fraction	dimensionless	dimensionless
9	Water weight fraction	dimensionless	dimensionless
10	Air weight fraction	dimensionless	dimensionless
11	Humidity ratio	kg moisture/kg dry air	lb moisture/lb dry air
12	Saturation humidity ratio	kg moisture/kg dry air	lb moisture/lb dry air
13	Relative humidity	dimensionless	dimensionless
14	Volume of dry air	m³/kg dry air	ft³/lb dry air
15	Volume of moist air	m³/kg dry air	ft³/lb dry air
16	Volume of condensed water or ice	m³/kg	ft³/lb
17	Volume of steam	m³/kg	ft³/lb
18	Enthalpy of dry air	kJ/kg dry air	Btu/lb dry air
19	Enthalpy of moist air	kJ/kg dry air	Btu/lb dry air
20	Enthalpy of condensed water or ice	kJ/kg	Btu/lb
21	Enthalpy of steam	kJ/kg	Btu/lb
22	Entropy of dry air	kJ/(kg dry air·°C)	Btu/(lb dry air·°F)
23	Entropy of moist air	kJ/(kg dry air·°C)	Btu/(lb dry air·°F)
24	Entropy of condensed water or ice	kJ/(kg dry air·°C)	Btu/(lb dry air·°F)
25	Entropy of steam	kJ/(kg·°C)	Btu/(lb·°F)

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MoistAirTab™ Functions