[TPHI_HX] Temperature and relative humidity to enthalpy and absolute humidity

Function block HX_TPHI uses the input values for temperature, relative humidity, and air pressure to calculate specific enthalpy and absolute humidity.

TPHI_HX uses input values for temperature, relative air humidity, and air pressure to calculate the specific enthalpy, absolute humidity, dew point temperature and enthalpy at dew point. The unit system is provided as an integer.

Functioning

TPHI_HX requires temperature [T], relative air humidity [HuRel], and air pressure [AP] at the inputs. Air pressure can be set up as a fixed value if unavailable as a measured value. Air pressure declines with an increase in altitude above sea level. As a result, consider the dependence of air pressure on the altitude above sea level.

Altitude above sea level [m]	Air pressure [bar]
0	1.013
300	0.978
600	0.943
900	0.910
1200	0.877
1500	0.846
1800	0.815
2100	0.785

When [EnTWet] is set to 1, TPHI_HX calculates the web bulb temperature and provides the results at output [TWet].

When [EnTWet] is set to 0, output [TWet] is set to value 0.0.

Specific enthalpy

The specific enthalpy [E] is calculated from the input values temperature [T], relative air humidity [HuRel], and air pressure [AP]. The enthalpy calculation can be used to calculate the energy level. For example, to determine whether it makes sense for the energy recovery unit to heat or cool based on the calculated energy for extract air and outside air.

Dew point temperature

The dew point temperature [TDwp] is calculated from the input values temperature [T], relative air humidity [HuRel], and air pressure [AP]. The calculation of the dew point temperature can be used to prevent condensation.

Dew point enthalpy

The dew point enthalpy [TDwp] is calculated from the input values temperature [T], relative air humidity [HuRel], and air pressure [AP]. The calculation of the dew point enthalpy can be used to determine the air state at which humidification would have no effect.

Wet bulb temperature.

The wet-bulb temperature is calculated from the input values temperature [T], relative air humidity [HuRel], and air pressure [AP]. The wet-bulb temperature [TWet] can be used to calculate the lowest temperature that can be achieved using water evaporative cooling.

Pins

Input	Description	Data type	Default value Value range
T	Temperature	Real	20.0 [°C] 68.0 [°F] -50.0…150.0 [°C] -58.0…302.0 [°F]
HuRel	Relative humidity	Real	50.0 [%] 0.0…100.0 [%]
AP	Air pressure	Real	0.960 [bar] 28.35 [inHg] 0.000...4.000 [bar] 0.00...118.12 [inHg]
EnTWet	Enable wet-bulb temperature	Boolean	0
EnTWet	0 - No 1 - Yes

Output	Description	Data type	Default value Value range
E	Specific enthalpy	Real	40.0 [kJ/kg] 24.9 [Btu/lb] 0.0…100.0 [kJ/kg] 7.7…50.7 [Btu/lb]
HuAbs	Absolute humidity, humidity ratio	Real	7.8 [g/kg] 0.008 [lb/lbda] 0.0…20.0 [g/kg] 0.000…0.020 [lb/lbda]
TDwp	Dew point temperature	Real	9.5 [°C] 49.1 [°F] -50.0…150.0 [°C] -58.0…302.0 [°F]
EDwp	Enthalpy at dew point	Real	29.0 [kJ/kg] 20.2 [Btu/lb] -50.0…150.0 [kJ/kg] -13.8…72.2 [Btu/lb]
ADen	Air density	Real	1.2 [kg/m³] 0.07 [lb/ft3] 0.0…5.0 [kg/m³] 0.00…0.31 [lb/ft3]
TWet	Wet-bulb temperature	Real	13.8 [°C] 56.8 [°F] -50.0…150.0 [°C] -58.0…302.0 [°F]
SysUnits	System of units Indicates the system of units used by the block.	Integer	1: International system of units (SI) (fallback) 1...5
SysUnits	1: International system of units (SI) (fallback) 2: International system of units (SI) 3: US system of units 4: Imperial system of units 5: Canadian system of units
ErrCode	Error code indication	Integer	0: No error
ErrCode	= 0 - No error > 0 - Error codes