Since for any process calculation only enthalpy difference (in and out of a process) is important, the reference point doesn't really matter. On some psychrometric charts (especially in the US) the reference state (zero enthalpy) is set at 0 ☏.Īs a consequence, enthalpy and entropy values calculated by the library will be shifted on these charts for the difference between the reference points. In the used formulations for calculation of thermodynamic properties of moist air, the reference state (zero enthalpy) is set at 0 ☌. In other words, moist air properties are valid for any dry-bulb temperatures below or equal to the saturation temperature of water at the same given absolute pressure, above that limit saturated moist air cannot exist. However, for any given absolute pressure, the highest temperature cannot exceed that temperature at which the saturation vapor pressure equals the absolute pressure. The upper limit of the absolute pressure is set at 5 MPa, and the temperature is restricted to the range -100 to 200☌. The entire set of equations used by the Humid Air application, is defined by the following temperature and pressure range: Wexler, ASHRAE Transactions, 89(2A) 520-535, 1983.Ĭalculable properties in SI or E units - HumidAir Application v2.5 1 Dry bulb temperature 2 Wet bulb temperature 3 Dew point temperature 4 Pressure 5 Saturation water pressure 6 Saturation pressure at wet bulb temperature 7 Saturation pressure at dew point temperature 8 Mole fraction of water 9 Mole fraction of air 10 Weight fraction of water 11 Weight fraction of air 12 Humidity ratio 13 Saturation humidity ratio 14 Degree of saturation 15 Relative humidity 16 Specific volume of dry air 17 Specific volume of saturated ice 18 Specific volume of saturated water 19 Specific volume of saturated vapor 20 Specific volume of moist air 21 Specific density of dry air 22 Specific density of saturated ice 23 Specific density of saturated water 24 Specific density of saturated vapor 25 Specific density of moist air 26 Specific enthalpy of dry air 27 Specific enthalpy of saturated ice 28 Specific enthalpy of saturated water 29 Specific enthalpy of saturated vapor 30 Specific enthalpy of moist air 31 Specific entropy of dry air 32 Specific entropy of saturated ice 33 Specific entropy of saturated water 34 Specific entropy of saturated vapor 35 Specific entropy of moist air
The following figure shows the HumidAir application.
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