public double GetWetBulbFromDryBulbHumidityAndPressure(double dryBulbTemperature, double humidity, double totalPressure)
{
dryBulbTemperature = moistureProperties.GetModifiedTemperature(dryBulbTemperature);
//Note: the convergence speed of the iteration procedure used in this method is very good.
//It has a better convergence speed than Newton method.
double dampingFactor = 0.5;
if (dryBulbTemperature <= 273.15 && dryBulbTemperature > 263.15)
{
dampingFactor = 0.75;
}
else if (dryBulbTemperature <= 263.15 && dryBulbTemperature > 258.15)
{
dampingFactor = 0.85;
}
else if (dryBulbTemperature <= 258.15)
{
dampingFactor = 0.95;
}
int counter = 0;
double tempDiff;
double saturationHumidityAtWetBulb;
double evapHeat;
double pSaturationAtWetBulb;
double wetBulbTemperatureOld;
double cpGas = GetSpecificHeatOfDryGas();
double cpMoisture = moistureProperties.GetSpecificHeatOfVapor();
double psychrometricRatio = 1.0;
//intial estimate of the wet bulb temperature is 5 degrees lower than dry bulb temperature
double wetBulbTemperature = dryBulbTemperature - 5;
do
{
counter++;
psychrometricRatio = CalculatePsychrometricRatio(dryBulbTemperature, wetBulbTemperature, humidity, totalPressure);
evapHeat = moistureProperties.GetEvaporationHeat(wetBulbTemperature);
evapHeat *= psychrometricRatio;
saturationHumidityAtWetBulb = (cpGas + cpMoisture * humidity) / (evapHeat) * (dryBulbTemperature - wetBulbTemperature) + humidity;
pSaturationAtWetBulb = totalPressure * saturationHumidityAtWetBulb / (moistureGasMolarMassRatio + saturationHumidityAtWetBulb);
wetBulbTemperatureOld = wetBulbTemperature;
wetBulbTemperature = moistureProperties.GetSaturationTemperature(pSaturationAtWetBulb);
tempDiff = wetBulbTemperature - wetBulbTemperatureOld;
wetBulbTemperature = wetBulbTemperature - dampingFactor * tempDiff;
//cpGas = gasProperties.GetSpecificHeatOfDryGas((dryBulbTemperature + wetBulbTemperature) / 2.0);
//cpMoisture = moistureProperties.GetSpecificHeatOfVapor((dryBulbTemperature + wetBulbTemperature) / 2.0);
cpGas = gasProperties.GetMeanSpecificHeatOfDryGas(dryBulbTemperature, wetBulbTemperature);
cpMoisture = moistureProperties.GetMeanSpecificHeatOfVapor(dryBulbTemperature, wetBulbTemperature);
} while(counter < 500 && Math.Abs(tempDiff / wetBulbTemperature) > 1.0e-6);
if (counter == 500)
{
throw new CalculationFailedException("Calculation of wet-bulb temperature from dry-bulb temperature and humidity failed.");
}
return(wetBulbTemperature);
}
//this is a generic constructor for all possible drying gases
/*public HumidGasCalculator(double moistureMolarMass, double gasMolarMass, double specificHeatOfMoisture, double specificHeatOfDryGas) {
* this.moistureMolarMass = moistureMolarMass;
* this.gasMolarMass = gasMolarMass;
* this.specificHeatOfMoisture = moistureProperties.GetSpecificHeatOfVapor();
* this.specificHeatOfDryGas = gasProperties.GetSpecificHeatOfDryGas();
* moistureGasMolarMassRatio = moistureMolarMass/gasMolarMass;
* }*/
public double GetHumidityFromDryBulbWetBulbAndPressure(double dryBulbTemperature, double wetBulbTemperature, double totalPressure)
{
double pSaturation = moistureProperties.GetSaturationPressure(wetBulbTemperature);
double saturationHumidity = moistureGasMolarMassRatio * pSaturation / (totalPressure - pSaturation);
double evapHeat = moistureProperties.GetEvaporationHeat(wetBulbTemperature);
double cpGas = gasProperties.GetSpecificHeatOfDryGas((dryBulbTemperature + wetBulbTemperature) / 2.0);
double cpMoisture = moistureProperties.GetSpecificHeatOfVapor((dryBulbTemperature + wetBulbTemperature) / 2.0);
double humidity = (evapHeat * saturationHumidity - cpGas * (dryBulbTemperature - wetBulbTemperature)) /
(evapHeat + cpMoisture * (dryBulbTemperature - wetBulbTemperature));
return(humidity);
}
//this is a generic constructor for all possible drying gases
/*public HumidGasCalculator(double moistureMolarMass, double gasMolarMass, double specificHeatOfMoisture, double specificHeatOfDryGas) {
* this.moistureMolarMass = moistureMolarMass;
* this.gasMolarMass = gasMolarMass;
* this.specificHeatOfMoisture = moistureProperties.GetSpecificHeatOfVapor();
* this.specificHeatOfDryGas = gasProperties.GetSpecificHeatOfDryGas();
* moistureGasMolarMassRatio = moistureMolarMass/gasMolarMass;
* }*/
public double GetHumidityFromDryBulbWetBulbAndPressure(double dryBulbTemperature, double wetBulbTemperature, double totalPressure)
{
//double pSaturation = moistureProperties.GetSaturationPressure(wetBulbTemperature);
//double saturationHumidity = moistureGasMolarMassRatio * pSaturation / (totalPressure - pSaturation);
double saturationHumidity = GetHumidityFromDewPointAndPressure(wetBulbTemperature, totalPressure);
double evapHeat = moistureProperties.GetEvaporationHeat(wetBulbTemperature);
double humidity = 0.01;
double humidity_old;
double cpGas;
double cpMoisture;
double psychrometricRatio = 1.0;
double evapHeatSigma;
int counter = 0;
do
{
psychrometricRatio = CalculatePsychrometricRatio(dryBulbTemperature, wetBulbTemperature, humidity, totalPressure);
evapHeatSigma = evapHeat * psychrometricRatio;
cpGas = gasProperties.GetSpecificHeatOfDryGas((dryBulbTemperature + wetBulbTemperature) / 2.0);
cpMoisture = moistureProperties.GetSpecificHeatOfVapor((dryBulbTemperature + wetBulbTemperature) / 2.0);
humidity_old = humidity;
humidity = (evapHeatSigma * saturationHumidity - cpGas * (dryBulbTemperature - wetBulbTemperature)) /
(evapHeatSigma + cpMoisture * (dryBulbTemperature - wetBulbTemperature));
} while (Math.Abs(humidity - humidity_old) / humidity > 1.0e-6 && counter < 200);
if (counter == 200)
{
throw new CalculationFailedException("Calculation of humidity from dry-bulb and wet-bulb temperatures failed.");
}
return(humidity);
}
