Enthalpy

Function

Calculate enthalpy “Out Enthalpy” and absolute humidity “Out Abs. Humidity” as a function of air temperature, relative air humidity, and air pressure. Use Enthalpy with the Economy function.

Formula

The absolute humidity is calculated according to the following formula:

“Out Abs. Humidity” = 622,0 * (“In Rel. Humidity”/100 * SPWV) / (“In Air Pressure” – “In Rel. Humidity”/100 * SPWV)


SPWV is the saturation pressure of water vapour (in mbar):
SPWV= 2,8868 * Exp(8,02 * Ln(1,098 + (“In Outside Air Temp.” / 100)))


The enthalpy is calculated with the formula:

“Out Enthalpy”: = 1,004 * “In Outside Air Temp.” + “Out Abs. Humidity”/ 1000 * (2501,6 + (1,86 * “In Outside Air Temp.”))


Fig. 169.   Wire-sheet Icon

Fig. 170.   Property Sheet

Fig. 171.   Slot Sheet


Inputs and Outputs

Table 115.   Inputs

Inputs

Type

Functional description

In Air Temp

numeric

outside air temperature in °C

In Rel. Humidity

numeric

relative humidity in percent (0 through 100 %)

In Air Pressure

numeric

air pressure (0,1 mbar …)

In Enabled

boolean

If the input “In Enabled” is set to false disabled in the slot sheet, the output “Out” will be disabled and is set to the value “0”.


Table 116.   Outputs

Outputs

Type

Functional description

Out Enthalpy

numeric

One analog output = dewpoint temperature

Out Absolute Humidity

numeric

absolute humidity (0 - 100 g/ kg)


Parameter List

No parameters