| Title: | Psychrometric Properties of Moist and Dry Air |
|---|---|
| Description: | Implementation of 'PsychroLib' <https://github.com/psychrometrics/psychrolib> library which contains functions to enable the calculation properties of moist and dry air in both metric (SI) and imperial (IP) systems of units. References: Meyer, D. and Thevenard, D (2019) <doi:10.21105/joss.01137>. |
| Authors: | Hongyuan Jia [aut, cre]  ,
The PsychroLib Contributors [ctb, cph] (Authors listed in
inst/PSYCHROLIB_AUTHORS.txt),
ASHRAE [cph] (Copyright 2017 ASHRAE Handbook Fundamentals
(https://www.ashrae.org) for equations and coefficients published
ASHRAE Handbook Fundamentals Chapter 1.) |
| Maintainer: | Hongyuan Jia <[email protected]> |
| License: | MIT + file LICENSE |
| Version: | 2.5.2 |
| Built: | 2025-01-31 03:08:10 UTC |
| Source: | https://github.com/hongyuanjia/psychrolib |
Contains functions for calculating thermodynamic properties of gas-vapor mixtures and standard atmosphere suitable for most engineering, physical and meteorological applications.
Most of the functions are an implementation of the formulae found in the 2017 ASHRAE Handbook - Fundamentals, in both International System (SI), and Imperial (IP) units. Please refer to the information included in each function for their respective reference.
psychroLib is a port of the psychrolib library for R.
psychrolib.units The default unit system. Should be
either be "SI" or "IP".
We have made every effort to ensure that the code is adequate, however, we make no representation with respect to its accuracy. Use at your own risk. Should you notice an error, or if you have a suggestion, please notify us through GitHub at https://github.com/psychrometrics/psychrolib/issues.
Hongyuan Jia and Jason Banfelder for R implementation.
D. Thevenard and D. Meyer for the core library implementations.
Equations and coefficients published ASHRAE Handbook — Fundamentals, Chapter 1 Copyright (c) 2017 ASHRAE Handbook — Fundamentals (https://www.ashrae.org)
Useful links:
Report bugs at https://github.com/psychrometrics/psychrolib/issues
library(psychrolib) # Set the unit system, for example to SI (can be either SI or IP) SetUnitSystem("SI") # Calculate the dew point temperature for a dry bulb temperature of 25 C # and a relative humidity of 80% GetTDewPointFromRelHum(25.0, 0.80)library(psychrolib) # Set the unit system, for example to SI (can be either SI or IP) SetUnitSystem("SI") # Calculate the dew point temperature for a dry bulb temperature of 25 C # and a relative humidity of 80% GetTDewPointFromRelHum(25.0, 0.80)
Utility function to calculate humidity ratio, wet-bulb temperature, dew-point temperature, vapour pressure, moist air enthalpy, moist air volume, and degree of saturation of air given dry-bulb temperature, relative humidity and pressure.
CalcPsychrometricsFromRelHum(TDryBulb, RelHum, Pressure)CalcPsychrometricsFromRelHum(TDryBulb, RelHum, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
RelHum |
A numeric vector of relative humidity in range [0, 1] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A list with named components for each psychrometric value computed:
Humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI]
Wet-bulb temperature in degreeF [IP] or degreeC [SI]
Dew-point temperature in degreeF [IP] or degreeC [SI]
Partial pressure of water vapor in moist air in Psi [IP] or Pa [SI]
Moist air enthalpy in Btu lb-1 [IP] or J kg-1 [SI]
Specific volume of moist air in ft3 lb-1 [IP] or in m3 kg-1 [SI]
Degree of saturation [unitless]
SetUnitSystem("IP") CalcPsychrometricsFromRelHum(80:100, 0.13, 14.69) SetUnitSystem("SI") CalcPsychrometricsFromRelHum(25:40, 0.5, 101325.0)SetUnitSystem("IP") CalcPsychrometricsFromRelHum(80:100, 0.13, 14.69) SetUnitSystem("SI") CalcPsychrometricsFromRelHum(25:40, 0.5, 101325.0)
Utility function to calculate humidity ratio, wet-bulb temperature, relative humidity, vapour pressure, moist air enthalpy, moist air volume, and degree of saturation of air given dry-bulb temperature, dew-point temperature, and pressure.
CalcPsychrometricsFromTDewPoint(TDryBulb, TDewPoint, Pressure)CalcPsychrometricsFromTDewPoint(TDryBulb, TDewPoint, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
TDewPoint |
A numeric vector of dew-point temperature in degreeF [IP] or degreeC [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A list with named components for each psychrometric value computed:
Humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI]
Wet-bulb temperature in degreeF [IP] or degreeC [SI]
Relative humidity in range [0, 1]
Partial pressure of water vapor in moist air in Psi [IP] or Pa [SI]
Moist air enthalpy in Btu lb-1 [IP] or J kg-1 [SI]
Specific volume of moist air in ft3 lb-1 [IP] or in m3 kg-1 [SI]
Degree of saturation [unitless]
SetUnitSystem("IP") CalcPsychrometricsFromTDewPoint(80:100, 40.0, 14.696) SetUnitSystem("SI") CalcPsychrometricsFromTDewPoint(25:40, 20.0, 101325.0)SetUnitSystem("IP") CalcPsychrometricsFromTDewPoint(80:100, 40.0, 14.696) SetUnitSystem("SI") CalcPsychrometricsFromTDewPoint(25:40, 20.0, 101325.0)
Utility function to calculate humidity ratio, dew-point temperature, relative humidity, vapour pressure, moist air enthalpy, moist air volume, and degree of saturation of air given dry-bulb temperature, wet-bulb temperature, and pressure.
CalcPsychrometricsFromTWetBulb(TDryBulb, TWetBulb, Pressure)CalcPsychrometricsFromTWetBulb(TDryBulb, TWetBulb, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
TWetBulb |
A numeric vector of wet-bulb temperature in degreeF [IP] or degreeC [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A list with named components for each psychrometric value computed:
Humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI]
Dew-point temperature in degreeF [IP] or degreeC [SI]
Relative humidity in range [0, 1]
Partial pressure of water vapor in moist air in Psi [IP] or Pa [SI]
Moist air enthalpy in Btu lb-1 [IP] or J kg-1 [SI]
Specific volume of moist air in ft3 lb-1 [IP] or in m3 kg-1 [SI]
Degree of saturation [unitless]
SetUnitSystem("IP") CalcPsychrometricsFromTWetBulb(80:100, 65.0, 14.696) SetUnitSystem("SI") CalcPsychrometricsFromTWetBulb(25:40, 20, 101325.0)SetUnitSystem("IP") CalcPsychrometricsFromTWetBulb(80:100, 65.0, 14.696) SetUnitSystem("SI") CalcPsychrometricsFromTWetBulb(25:40, 20, 101325.0)
Return the degree of saturation (i.e humidity ratio of the air / humidity ratio of the air at saturation at the same temperature and pressure) given dry-bulb temperature, humidity ratio, and atmospheric pressure.
GetDegreeOfSaturation(TDryBulb, HumRatio, Pressure)GetDegreeOfSaturation(TDryBulb, HumRatio, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
HumRatio |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of degree of saturation in arbitrary unit
This definition is absent from the 2017 Handbook. Using 2009 version instead.
ASHRAE Handbook - Fundamentals (2009) ch. 1 eqn 12
SetUnitSystem("IP") GetDegreeOfSaturation(80:100, 0.01, 14.175) SetUnitSystem("SI") GetDegreeOfSaturation(20:30, 0.01, 95461.0)SetUnitSystem("IP") GetDegreeOfSaturation(80:100, 0.01, 14.175) SetUnitSystem("SI") GetDegreeOfSaturation(20:30, 0.01, 95461.0)
Return dry-air density given dry-bulb temperature and pressure.
GetDryAirDensity(TDryBulb, Pressure)GetDryAirDensity(TDryBulb, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of dry air density in lb ft-3 [IP] or kg m-3 [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1
Eqn 14 for the perfect gas relationship for dry air.
Eqn 1 for the universal gas constant.
The factor 144 in IP is for the conversion of Psi = lb in-2 to lb ft-2.
SetUnitSystem("IP") GetDryAirDensity(77:87, 14.696) SetUnitSystem("SI") GetDryAirDensity(25:30, 101325)SetUnitSystem("IP") GetDryAirDensity(77:87, 14.696) SetUnitSystem("SI") GetDryAirDensity(25:30, 101325)
Return dry-air enthalpy given dry-bulb temperature.
GetDryAirEnthalpy(TDryBulb)GetDryAirEnthalpy(TDryBulb)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
A numeric vector of dry air enthalpy in Btu lb-1 [IP] or J kg-1 [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 28
SetUnitSystem("IP") GetDryAirEnthalpy(77:87) SetUnitSystem("SI") GetDryAirEnthalpy(10:30)SetUnitSystem("IP") GetDryAirEnthalpy(77:87) SetUnitSystem("SI") GetDryAirEnthalpy(10:30)
Return dry-air volume given dry-bulb temperature and pressure.
GetDryAirVolume(TDryBulb, Pressure)GetDryAirVolume(TDryBulb, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of dry air volume in ft3 lb-1 [IP] or in m3 kg-1 [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1
Eqn 14 for the perfect gas relationship for dry air.
Eqn 1 for the universal gas constant.
The factor 144 in IP is for the conversion of Psi = lb in-2 to lb ft-2.
SetUnitSystem("IP") GetDryAirVolume(77:87, 14.696) SetUnitSystem("SI") GetDryAirVolume(25:30, 101325)SetUnitSystem("IP") GetDryAirVolume(77:87, 14.696) SetUnitSystem("SI") GetDryAirVolume(25:30, 101325)
Return humidity ratio from enthalpy and dry-bulb temperature.
GetHumRatioFromEnthalpyAndTDryBulb(MoistAirEnthalpy, TDryBulb)GetHumRatioFromEnthalpyAndTDryBulb(MoistAirEnthalpy, TDryBulb)
MoistAirEnthalpy |
A numeric vector of moist air enthalpy in Btu lb-1 [IP] or J kg-1 |
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI]
Based on the GetMoistAirEnthalpy function, rearranged for humidity ratio.
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 30.
SetUnitSystem("IP") GetHumRatioFromEnthalpyAndTDryBulb(42.6168, 76:86) SetUnitSystem("SI") GetHumRatioFromEnthalpyAndTDryBulb(81316.0, 20:30)SetUnitSystem("IP") GetHumRatioFromEnthalpyAndTDryBulb(42.6168, 76:86) SetUnitSystem("SI") GetHumRatioFromEnthalpyAndTDryBulb(81316.0, 20:30)
Return humidity ratio given dry-bulb temperature, relative humidity, and pressure.
GetHumRatioFromRelHum(TDryBulb, RelHum, Pressure)GetHumRatioFromRelHum(TDryBulb, RelHum, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
RelHum |
A numeric vector of relative humidity in range [0, 1] |
Pressure |
A numeric vector of atmospheric Pressure in Psi [IP] or Pa [SI] |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1
SetUnitSystem("IP") GetHumRatioFromRelHum(80:100, 0.5, 14.175) SetUnitSystem("SI") GetHumRatioFromRelHum(20:30, 0.5, 95461.0)SetUnitSystem("IP") GetHumRatioFromRelHum(80:100, 0.5, 14.175) SetUnitSystem("SI") GetHumRatioFromRelHum(20:30, 0.5, 95461.0)
Return the humidity ratio (aka mixing ratio) from specific humidity.
GetHumRatioFromSpecificHum(SpecificHum)GetHumRatioFromSpecificHum(SpecificHum)
SpecificHum |
A numeric vector of specific humidity in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI] |
A numeric vector of humidity ratio in lb_H2O lb_Dry_Air-1 [IP] or kg_H2O kg_Dry_Air-1 [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 9b (solved for humidity ratio)
SetUnitSystem("IP") GetHumRatioFromSpecificHum(seq(0.006, 0.016, 0.001)) SetUnitSystem("SI") GetHumRatioFromSpecificHum(seq(0.006, 0.016, 0.001))SetUnitSystem("IP") GetHumRatioFromSpecificHum(seq(0.006, 0.016, 0.001)) SetUnitSystem("SI") GetHumRatioFromSpecificHum(seq(0.006, 0.016, 0.001))
Return humidity ratio given dew-point temperature and pressure.
GetHumRatioFromTDewPoint(TDewPoint, Pressure)GetHumRatioFromTDewPoint(TDewPoint, Pressure)
TDewPoint |
A numeric vector of dew-point temperature in degreeF [IP] or degreeC [SI] |
Pressure |
A numeric vector of atmospheric Pressure in Psi [IP] or Pa [SI] |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 13
SetUnitSystem("IP") GetHumRatioFromTDewPoint(50:80, 14.175) SetUnitSystem("SI") GetHumRatioFromTDewPoint(20:30, 95461.0)SetUnitSystem("IP") GetHumRatioFromTDewPoint(50:80, 14.175) SetUnitSystem("SI") GetHumRatioFromTDewPoint(20:30, 95461.0)
Return humidity ratio given dry-bulb temperature, wet-bulb temperature, and pressure.
GetHumRatioFromTWetBulb(TDryBulb, TWetBulb, Pressure)GetHumRatioFromTWetBulb(TDryBulb, TWetBulb, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
TWetBulb |
A numeric vector of wet-bulb temperature in degreeF [IP] or degreeC [SI] |
Pressure |
A numeric vector of atmospheric Pressure in Psi [IP] or Pa [SI] |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 33 and 35
SetUnitSystem("IP") GetHumRatioFromTWetBulb(80:100, 77.0, 14.175) SetUnitSystem("SI") GetHumRatioFromTWetBulb(20:30, 19.0, 95461.0)SetUnitSystem("IP") GetHumRatioFromTWetBulb(80:100, 77.0, 14.175) SetUnitSystem("SI") GetHumRatioFromTWetBulb(20:30, 19.0, 95461.0)
Return humidity ratio given water vapor pressure and atmospheric pressure.
GetHumRatioFromVapPres(VapPres, Pressure)GetHumRatioFromVapPres(VapPres, Pressure)
VapPres |
A numeric vector of partial pressure of water vapor in moist air in Psi [IP] or Pa [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 20
SetUnitSystem("IP") GetHumRatioFromVapPres(seq(0.4, 0.6, 0.01), 14.175) SetUnitSystem("SI") GetHumRatioFromVapPres(seq(3000, 4000, 100), 95461)SetUnitSystem("IP") GetHumRatioFromVapPres(seq(0.4, 0.6, 0.01), 14.175) SetUnitSystem("SI") GetHumRatioFromVapPres(seq(3000, 4000, 100), 95461)
Return moist air density given humidity ratio, dry bulb temperature, and pressure.
GetMoistAirDensity(TDryBulb, HumRatio, Pressure)GetMoistAirDensity(TDryBulb, HumRatio, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
HumRatio |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of moistAirDensity: Moist air density in lb ft-3 [IP] or kg m-3 [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 11
SetUnitSystem("IP") GetMoistAirDensity(80:100, 0.02, 14.175) SetUnitSystem("SI") GetMoistAirDensity(20:30, 0.02, 95461)SetUnitSystem("IP") GetMoistAirDensity(80:100, 0.02, 14.175) SetUnitSystem("SI") GetMoistAirDensity(20:30, 0.02, 95461)
Return moist air enthalpy given dry-bulb temperature and humidity ratio.
GetMoistAirEnthalpy(TDryBulb, HumRatio)GetMoistAirEnthalpy(TDryBulb, HumRatio)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
HumRatio |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI] |
A numeric vector of moist air enthalpy in Btu lb-1 [IP] or J kg-1
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 30
SetUnitSystem("IP") GetMoistAirEnthalpy(80:100, 0.02) SetUnitSystem("SI") GetMoistAirEnthalpy(20:30, 0.02)SetUnitSystem("IP") GetMoistAirEnthalpy(80:100, 0.02) SetUnitSystem("SI") GetMoistAirEnthalpy(20:30, 0.02)
Return moist air specific volume given dry-bulb temperature, humidity ratio, and pressure.
GetMoistAirVolume(TDryBulb, HumRatio, Pressure)GetMoistAirVolume(TDryBulb, HumRatio, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
HumRatio |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of specific volume of moist air in ft3 lb-1 of dry air [IP] or in m3 kg-1 of dry air [SI]
In IP units, R_DA_IP / 144 equals 0.370486 which is the coefficient appearing in eqn 26.
The factor 144 is for the conversion of Psi = lb in-2 to lb ft-2.
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 26
SetUnitSystem("IP") GetMoistAirVolume(80:100, 0.02, 14.175) SetUnitSystem("SI") GetMoistAirVolume(20:30, 0.02, 95461)SetUnitSystem("IP") GetMoistAirVolume(80:100, 0.02, 14.175) SetUnitSystem("SI") GetMoistAirVolume(20:30, 0.02, 95461)
Return relative humidity given dry-bulb temperature, humidity ratio, and pressure.
GetRelHumFromHumRatio(TDryBulb, HumRatio, Pressure)GetRelHumFromHumRatio(TDryBulb, HumRatio, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
HumRatio |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI] |
Pressure |
A numeric vector of atmospheric Pressure in Psi [IP] or Pa [SI] |
A numeric vector of relative humidity in range [0, 1]
ASHRAE Handbook - Fundamentals (2017) ch. 1
SetUnitSystem("IP") GetRelHumFromHumRatio(80:100, 0.01, 14.175) SetUnitSystem("SI") GetRelHumFromHumRatio(20:30, 0.01, 95461.0)SetUnitSystem("IP") GetRelHumFromHumRatio(80:100, 0.01, 14.175) SetUnitSystem("SI") GetRelHumFromHumRatio(20:30, 0.01, 95461.0)
Return relative humidity given dry-bulb temperature and dew-point temperature.
GetRelHumFromTDewPoint(TDryBulb, TDewPoint)GetRelHumFromTDewPoint(TDryBulb, TDewPoint)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
TDewPoint |
A numeric vector of dew-point temperature in degreeF [IP] or degreeC [SI] |
A numeric vector of relative humidity in range [0, 1]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 22
SetUnitSystem("IP") GetRelHumFromTDewPoint(80:100, 65) SetUnitSystem("SI") GetRelHumFromTDewPoint(20:30, 15)SetUnitSystem("IP") GetRelHumFromTDewPoint(80:100, 65) SetUnitSystem("SI") GetRelHumFromTDewPoint(20:30, 15)
Return relative humidity given dry-bulb temperature, wet bulb temperature and pressure.
GetRelHumFromTWetBulb(TDryBulb, TWetBulb, Pressure)GetRelHumFromTWetBulb(TDryBulb, TWetBulb, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
TWetBulb |
A numeric vector of wet-bulb temperature in degreeF [IP] or degreeC [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of relative humidity in range [0, 1]
ASHRAE Handbook - Fundamentals (2017) ch. 1
SetUnitSystem("IP") GetRelHumFromTWetBulb(80:100, 79.9, 14.696) SetUnitSystem("SI") GetRelHumFromTWetBulb(25:40, 20, 101325.0)SetUnitSystem("IP") GetRelHumFromTWetBulb(80:100, 79.9, 14.696) SetUnitSystem("SI") GetRelHumFromTWetBulb(25:40, 20, 101325.0)
Return relative humidity given dry-bulb temperature and vapor pressure.
GetRelHumFromVapPres(TDryBulb, VapPres)GetRelHumFromVapPres(TDryBulb, VapPres)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
VapPres |
A numeric vector of partial pressure of water vapor in moist air in Psi [IP] or Pa [SI] |
A numeric vector of relative humidity in range [0, 1]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 12, 22
SetUnitSystem("IP") GetRelHumFromVapPres(70:80, 0.0149) SetUnitSystem("SI") GetRelHumFromVapPres(20:30, 12581)SetUnitSystem("IP") GetRelHumFromVapPres(70:80, 0.0149) SetUnitSystem("SI") GetRelHumFromVapPres(20:30, 12581)
Return saturated air enthalpy given dry-bulb temperature and pressure.
GetSatAirEnthalpy(TDryBulb, Pressure)GetSatAirEnthalpy(TDryBulb, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of saturated air enthalpy in Btu lb-1 [IP] or J kg-1 [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1
SetUnitSystem("IP") GetSatAirEnthalpy(80:100, 14.696) SetUnitSystem("SI") GetSatAirEnthalpy(20:30, 101325)SetUnitSystem("IP") GetSatAirEnthalpy(80:100, 14.696) SetUnitSystem("SI") GetSatAirEnthalpy(20:30, 101325)
Return humidity ratio of saturated air given dry-bulb temperature and pressure.
GetSatHumRatio(TDryBulb, Pressure)GetSatHumRatio(TDryBulb, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of humidity ratio of saturated air in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 36, solved for W
SetUnitSystem("IP") GetSatHumRatio(80:100, 14.696) SetUnitSystem("SI") GetSatHumRatio(20:30, 101325)SetUnitSystem("IP") GetSatHumRatio(80:100, 14.696) SetUnitSystem("SI") GetSatHumRatio(20:30, 101325)
Return saturation vapor pressure given dry-bulb temperature.
GetSatVapPres(TDryBulb)GetSatVapPres(TDryBulb)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
A numeric vector of vapor pressure of saturated air in Psi [IP] or Pa [SI]
Important note: the ASHRAE formulae are defined above and below the freezing point but have a discontinuity at the freezing point. This is a small inaccuracy on ASHRAE's part: the formulae should be defined above and below the triple point of water (not the feezing point) in which case the discontinuity vanishes. It is essential to use the triple point of water otherwise function GetTDewPointFromVapPres, which inverts the present function, does not converge properly around the freezing point.
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 5 & 6
SetUnitSystem("IP") GetSatVapPres(80:100) SetUnitSystem("SI") GetSatVapPres(20:30)SetUnitSystem("IP") GetSatVapPres(80:100) SetUnitSystem("SI") GetSatVapPres(20:30)
Return sea level pressure given dry-bulb temperature, altitude above sea level and pressure.
GetSeaLevelPressure(StationPressure, Altitude, TDryBulb)GetSeaLevelPressure(StationPressure, Altitude, TDryBulb)
StationPressure |
A numeric vector of observed station pressure in Psi [IP] or Pa [SI] |
Altitude |
A numeric vector of altitude in ft [IP] or m [SI] |
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
A numeric vector of sea level barometric pressure in Psi [IP] or Pa [SI]
The standard procedure for the US is to use for TDryBulb the average of the current station temperature and the station temperature from 12 hours ago.
Hess SL, Introduction to theoretical meteorology, Holt Rinehart and Winston, NY 1959, ch. 6.5; Stull RB, Meteorology for scientists and engineers, 2nd edition, Brooks/Cole 2000, ch. 1.
SetUnitSystem("IP") GetSeaLevelPressure(14.68, 300:400, 62.94) SetUnitSystem("SI") GetSeaLevelPressure(101226.5, 105:205, 17.19)SetUnitSystem("IP") GetSeaLevelPressure(14.68, 300:400, 62.94) SetUnitSystem("SI") GetSeaLevelPressure(101226.5, 105:205, 17.19)
Return the specific humidity from humidity ratio (aka mixing ratio).
GetSpecificHumFromHumRatio(HumRatio)GetSpecificHumFromHumRatio(HumRatio)
HumRatio |
A numeric vector of humidity ratio in lb_H2O lb_Dry_Air-1 [IP] or kg_H2O kg_Dry_Air-1 [SI] |
A numeric vector of specific humidity in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 9b
SetUnitSystem("IP") GetSpecificHumFromHumRatio(seq(0.006, 0.016, 0.001)) SetUnitSystem("SI") GetSpecificHumFromHumRatio(seq(0.006, 0.016, 0.001))SetUnitSystem("IP") GetSpecificHumFromHumRatio(seq(0.006, 0.016, 0.001)) SetUnitSystem("SI") GetSpecificHumFromHumRatio(seq(0.006, 0.016, 0.001))
Return standard atmosphere barometric pressure, given the elevation (altitude).
GetStandardAtmPressure(Altitude)GetStandardAtmPressure(Altitude)
Altitude |
A numeric vector of altitude in ft [IP] or m [SI] |
A numeric vector of standard atmosphere barometric pressure in Psi [IP] or Pa [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 3
SetUnitSystem("IP") GetStandardAtmPressure(seq(-500, 1000, 100)) SetUnitSystem("SI") GetStandardAtmPressure(seq(-500, 1000, 100))SetUnitSystem("IP") GetStandardAtmPressure(seq(-500, 1000, 100)) SetUnitSystem("SI") GetStandardAtmPressure(seq(-500, 1000, 100))
Return standard atmosphere temperature, given the elevation (altitude).
GetStandardAtmTemperature(Altitude)GetStandardAtmTemperature(Altitude)
Altitude |
A numeric vector of altitude in ft [IP] or m [SI] |
A numeric vector of standard atmosphere dry-bulb temperature in degreeF [IP] or degreeC [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 4
SetUnitSystem("IP") GetStandardAtmTemperature(seq(-500, 1000, 100)) SetUnitSystem("SI") GetStandardAtmTemperature(seq(-500, 1000, 100))SetUnitSystem("IP") GetStandardAtmTemperature(seq(-500, 1000, 100)) SetUnitSystem("SI") GetStandardAtmTemperature(seq(-500, 1000, 100))
Return station pressure from sea level pressure.
GetStationPressure(SeaLevelPressure, Altitude, TDryBulb)GetStationPressure(SeaLevelPressure, Altitude, TDryBulb)
SeaLevelPressure |
A numeric vector of sea level barometric pressure in Psi [IP] or Pa [SI] |
Altitude |
A numeric vector of altitude in ft [IP] or m [SI] |
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
A numeric vector of station pressure in Psi [IP] or Pa [SI]
This function is just the inverse of GetSeaLevelPressure.
See GetSeaLevelPressure.
SetUnitSystem("IP") GetStationPressure(14.68, 300:400, 62.94) SetUnitSystem("SI") GetStationPressure(101226.5, 105:205, 17.19)SetUnitSystem("IP") GetStationPressure(14.68, 300:400, 62.94) SetUnitSystem("SI") GetStationPressure(101226.5, 105:205, 17.19)
Utility function to convert temperature to degree Celsius (degreeC) given temperature in Kelvin (K).
GetTCelsiusFromTKelvin(TKelvin)GetTCelsiusFromTKelvin(TKelvin)
TKelvin |
A numeric vector of temperature in degree Kelvin (K) |
A numeric vector of temperature in Celsius (degreeC)
Exact conversion.
ASHRAE Handbook - Fundamentals (2017) ch. 1 section 3
GetTCelsiusFromTKelvin(300:400)GetTCelsiusFromTKelvin(300:400)
Return dew-point temperature given dry-bulb temperature, humidity ratio, and pressure.
GetTDewPointFromHumRatio(TDryBulb, HumRatio, Pressure)GetTDewPointFromHumRatio(TDryBulb, HumRatio, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
HumRatio |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI] |
Pressure |
A numeric vector of atmospheric Pressure in Psi [IP] or Pa [SI] |
A numeric vector of dew-point temperature in degreeF [IP] or degreeC [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1
SetUnitSystem("IP") GetTDewPointFromHumRatio(80:100, 0.01, 14.175) SetUnitSystem("SI") GetTDewPointFromHumRatio(20:30, 0.01, 95461.0)SetUnitSystem("IP") GetTDewPointFromHumRatio(80:100, 0.01, 14.175) SetUnitSystem("SI") GetTDewPointFromHumRatio(20:30, 0.01, 95461.0)
Return dew-point temperature given dry-bulb temperature and relative humidity.
GetTDewPointFromRelHum(TDryBulb, RelHum)GetTDewPointFromRelHum(TDryBulb, RelHum)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
RelHum |
A numeric vector of relative humidity in range [0, 1] |
A numeric vector of dew-point temperature in degreeF [IP] or degreeC [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1
SetUnitSystem("IP") GetTDewPointFromRelHum(80:100, 0.2) SetUnitSystem("SI") GetTDewPointFromRelHum(20:30, 0.4)SetUnitSystem("IP") GetTDewPointFromRelHum(80:100, 0.2) SetUnitSystem("SI") GetTDewPointFromRelHum(20:30, 0.4)
Return dew-point temperature given dry-bulb temperature, wet-bulb temperature, and pressure.
GetTDewPointFromTWetBulb(TDryBulb, TWetBulb, Pressure)GetTDewPointFromTWetBulb(TDryBulb, TWetBulb, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
TWetBulb |
A numeric vector of wet-bulb temperature in degreeF [IP] or degreeC [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of dew-point temperature in degreeF [IP] or degreeC [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1
SetUnitSystem("IP") GetTDewPointFromTWetBulb(80:100, 65.0, 14.696) SetUnitSystem("SI") GetTDewPointFromTWetBulb(25:40, 20, 101325.0)SetUnitSystem("IP") GetTDewPointFromTWetBulb(80:100, 65.0, 14.696) SetUnitSystem("SI") GetTDewPointFromTWetBulb(25:40, 20, 101325.0)
Return dew-point temperature given dry-bulb temperature and vapor pressure.
GetTDewPointFromVapPres(TDryBulb, VapPres)GetTDewPointFromVapPres(TDryBulb, VapPres)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
VapPres |
A numeric vector of partial pressure of water vapor in moist air in Psi [IP] or Pa [SI] |
A numeric vector of dew-point temperature in degreeF [IP] or degreeC [SI]
The dew point temperature is solved by inverting the equation giving water vapor pressure at saturation from temperature rather than using the regressions provided by ASHRAE (eqn. 37 and 38), which are much less accurate and have a narrower range of validity.
The Newton-Raphson (NR) method is used on the logarithm of water vapour pressure as a function of temperature, which is a very smooth function.
Convergence is usually achieved in 3 to 5 iterations.
TDryBulb is not really needed here, just used for convenience.
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn. 5 and 6
SetUnitSystem("IP") GetTDewPointFromVapPres(70:80, seq(0.0149, 0.0249, 0.001)) SetUnitSystem("SI") GetTDewPointFromVapPres(70:80, 12581:12591)SetUnitSystem("IP") GetTDewPointFromVapPres(70:80, seq(0.0149, 0.0249, 0.001)) SetUnitSystem("SI") GetTDewPointFromVapPres(70:80, 12581:12591)
Return dry bulb temperature from enthalpy and humidity ratio.
GetTDryBulbFromEnthalpyAndHumRatio(MoistAirEnthalpy, HumRatio)GetTDryBulbFromEnthalpyAndHumRatio(MoistAirEnthalpy, HumRatio)
MoistAirEnthalpy |
A numeric vector of moist air enthalpy in Btu lb-1 [IP] or J kg-1 |
HumRatio |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI] |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI]
Based on the GetMoistAirEnthalpy function, rearranged for temperature.
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 30
SetUnitSystem("IP") GetTDryBulbFromEnthalpyAndHumRatio(42.6168, seq(0.01, 0.02, 0.001)) SetUnitSystem("SI") GetTDryBulbFromEnthalpyAndHumRatio(81316.0, seq(0.01, 0.02, 0.001))SetUnitSystem("IP") GetTDryBulbFromEnthalpyAndHumRatio(42.6168, seq(0.01, 0.02, 0.001)) SetUnitSystem("SI") GetTDryBulbFromEnthalpyAndHumRatio(81316.0, seq(0.01, 0.02, 0.001))
Return dry-bulb temperature given moist air specific volume, humidity ratio, and pressure.
GetTDryBulbFromMoistAirVolumeAndHumRatio(MoistAirVolume, HumRatio, Pressure)GetTDryBulbFromMoistAirVolumeAndHumRatio(MoistAirVolume, HumRatio, Pressure)
MoistAirVolume |
A numeric vector of specific volume of moist air in ft3 lb-1 of dry air [IP] or in m3 kg-1 of dry air [SI] |
HumRatio |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of tDryBulb : Dry-bulb temperature in degreeF [IP] or degreeC [SI]
In IP units, R_DA_IP / 144 equals 0.370486 which is the coefficient appearing in eqn 26.
The factor 144 is for the conversion of Psi = lb in-2 to lb ft-2.
Based on the 'GetMoistAirVolume' function, rearranged for dry-bulb temperature.
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 26
SetUnitSystem("IP") GetTDryBulbFromMoistAirVolumeAndHumRatio(14.72, seq(0.02, 0.03, 0.001), 14.175) SetUnitSystem("SI") GetTDryBulbFromMoistAirVolumeAndHumRatio(0.94, seq(0.02, 0.03, 0.001), 95461)SetUnitSystem("IP") GetTDryBulbFromMoistAirVolumeAndHumRatio(14.72, seq(0.02, 0.03, 0.001), 14.175) SetUnitSystem("SI") GetTDryBulbFromMoistAirVolumeAndHumRatio(0.94, seq(0.02, 0.03, 0.001), 95461)
Utility function to convert temperature to degree Fahrenheit (degreeF) given temperature in degree Rankine (degreeR).
GetTFahrenheitFromTRankine(TRankine)GetTFahrenheitFromTRankine(TRankine)
TRankine |
A numeric vector of temperature in degree Rankine (degreeR) |
A numeric vector of temperature in degree Fahrenheit (degreeF)
Exact conversion.
ASHRAE Handbook - Fundamentals (2017) ch. 1 section 3
GetTFahrenheitFromTRankine(500:600)GetTFahrenheitFromTRankine(500:600)
Utility function to convert temperature to Kelvin (K) given temperature in degree Celsius (degreeC).
GetTKelvinFromTCelsius(TCelsius)GetTKelvinFromTCelsius(TCelsius)
TCelsius |
A numeric vector of temperature in degree Celsius (degreeC) |
A numeric vector of temperature in Kelvin (K)
Exact conversion.
ASHRAE Handbook - Fundamentals (2017) ch. 1 section 3
GetTKelvinFromTCelsius(20:30)GetTKelvinFromTCelsius(20:30)
Utility function to convert temperature to degree Rankine (degreeR) given temperature in degree Fahrenheit (degreeF).
GetTRankineFromTFahrenheit(TFahrenheit)GetTRankineFromTFahrenheit(TFahrenheit)
TFahrenheit |
A numeric vector of temperature in degree Fahrenheit (degreeF) |
A numeric vector of temperature in degree Rankine (degreeR)
Exact conversion.
ASHRAE Handbook - Fundamentals (2017) ch. 1 section 3
GetTRankineFromTFahrenheit(1:100)GetTRankineFromTFahrenheit(1:100)
Return wet-bulb temperature given dry-bulb temperature, humidity ratio, and pressure.
GetTWetBulbFromHumRatio(TDryBulb, HumRatio, Pressure)GetTWetBulbFromHumRatio(TDryBulb, HumRatio, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
HumRatio |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI] |
Pressure |
A numeric vector of atmospheric Pressure in Psi [IP] or Pa [SI] |
A numeric vector of wet-bulb temperature in degreeF [IP] or degreeC [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 33 and 35 solved for Tstar
SetUnitSystem("IP") GetTWetBulbFromHumRatio(80:100, 0.01, 14.175) SetUnitSystem("SI") GetTWetBulbFromHumRatio(20:30, 0.01, 95461)SetUnitSystem("IP") GetTWetBulbFromHumRatio(80:100, 0.01, 14.175) SetUnitSystem("SI") GetTWetBulbFromHumRatio(20:30, 0.01, 95461)
Return wet-bulb temperature given dry-bulb temperature, relative humidity, and pressure.
GetTWetBulbFromRelHum(TDryBulb, RelHum, Pressure)GetTWetBulbFromRelHum(TDryBulb, RelHum, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
RelHum |
A numeric vector of relative humidity in range [0, 1] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of wet-bulb temperature in degreeF [IP] or degreeC [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1
SetUnitSystem("IP") GetTWetBulbFromRelHum(80:100, 0.2, 14.696) SetUnitSystem("SI") GetTWetBulbFromRelHum(25:40, 0.2, 101325.0)SetUnitSystem("IP") GetTWetBulbFromRelHum(80:100, 0.2, 14.696) SetUnitSystem("SI") GetTWetBulbFromRelHum(25:40, 0.2, 101325.0)
Return wet-bulb temperature given dry-bulb temperature, dew-point temperature, and pressure.
GetTWetBulbFromTDewPoint(TDryBulb, TDewPoint, Pressure)GetTWetBulbFromTDewPoint(TDryBulb, TDewPoint, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
TDewPoint |
A numeric vector of dew-point temperature in degreeF [IP] or degreeC [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of wet-bulb temperature in degreeF [IP] or degreeC [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1
SetUnitSystem("IP") GetTWetBulbFromTDewPoint(80:100, 40.0, 14.696) SetUnitSystem("SI") GetTWetBulbFromTDewPoint(25:40, 20.0, 101325.0)SetUnitSystem("IP") GetTWetBulbFromTDewPoint(80:100, 40.0, 14.696) SetUnitSystem("SI") GetTWetBulbFromTDewPoint(25:40, 20.0, 101325.0)
Return system of units in use.
GetUnitSystem()GetUnitSystem()
A string indicating system of units in use ("SI" or "IP")
Return Vapor pressure deficit given dry-bulb temperature, humidity ratio, and pressure.
GetVaporPressureDeficit(TDryBulb, HumRatio, Pressure)GetVaporPressureDeficit(TDryBulb, HumRatio, Pressure)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
HumRatio |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of vapor pressure deficit in Psi [IP] or Pa [SI]
Oke (1987) eqn 2.13a
SetUnitSystem("IP") GetVaporPressureDeficit(80:100, 0.01, 14.175) SetUnitSystem("SI") GetVaporPressureDeficit(20:30, 0.01, 95461.0)SetUnitSystem("IP") GetVaporPressureDeficit(80:100, 0.01, 14.175) SetUnitSystem("SI") GetVaporPressureDeficit(20:30, 0.01, 95461.0)
Return vapor pressure given humidity ratio and pressure.
GetVapPresFromHumRatio(HumRatio, Pressure)GetVapPresFromHumRatio(HumRatio, Pressure)
HumRatio |
A numeric vector of humidity ratio in lb_H2O lb_Air-1 [IP] or kg_H2O kg_Air-1 [SI] |
Pressure |
A numeric vector of atmospheric pressure in Psi [IP] or Pa [SI] |
A numeric vector of partial pressure of water vapor in moist air in Psi [IP] or Pa [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 20 solved for pw
SetUnitSystem("IP") GetVapPresFromHumRatio(seq(0.02, 0.03, 0.001), 14.175) SetUnitSystem("SI") GetVapPresFromHumRatio(seq(0.02, 0.03, 0.001), 95461)SetUnitSystem("IP") GetVapPresFromHumRatio(seq(0.02, 0.03, 0.001), 14.175) SetUnitSystem("SI") GetVapPresFromHumRatio(seq(0.02, 0.03, 0.001), 95461)
Return partial pressure of water vapor as a function of relative humidity and temperature.
GetVapPresFromRelHum(TDryBulb, RelHum)GetVapPresFromRelHum(TDryBulb, RelHum)
TDryBulb |
A numeric vector of dry-bulb temperature in degreeF [IP] or degreeC [SI] |
RelHum |
A numeric vector of relative humidity in range [0, 1] |
A numeric vector of partial pressure of water vapor in moist air in Psi [IP] or Pa [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 12, 22
SetUnitSystem("IP") GetVapPresFromRelHum(77, seq(0.1, 0.8, 0.1)) SetUnitSystem("SI") GetVapPresFromRelHum(20, seq(0.1, 0.8, 0.1))SetUnitSystem("IP") GetVapPresFromRelHum(77, seq(0.1, 0.8, 0.1)) SetUnitSystem("SI") GetVapPresFromRelHum(20, seq(0.1, 0.8, 0.1))
Return vapor pressure given dew point temperature.
GetVapPresFromTDewPoint(TDewPoint)GetVapPresFromTDewPoint(TDewPoint)
TDewPoint |
A numeric vector of dew-point temperature in degreeF [IP] or degreeC [SI] |
A numeric vector of partial pressure of water vapor in moist air in Psi [IP] or Pa [SI]
ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 36
SetUnitSystem("IP") GetVapPresFromTDewPoint(12:20) SetUnitSystem("SI") GetVapPresFromTDewPoint(12:20)SetUnitSystem("IP") GetVapPresFromTDewPoint(12:20) SetUnitSystem("SI") GetVapPresFromTDewPoint(12:20)
Check whether the system in use is IP or SI.
isIP()isIP()
TRUE if unit system is IP
Set the system of units to use (SI or IP).
SetUnitSystem(units)SetUnitSystem(units)
units |
A string indicating the system of units chosen. Should be either
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