[HX_TPHI] Enthalpy and absolute humidity to temperature and relative humidity

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

HX_TPHI uses the values for specific enthalpy, absolute humidity, and air pressure to calculate temperature and relative air humidity, condensed water amount in saturated air, and the effective enthalpy. The applied unit system is provided as integers.

Functioning

HX_TPHI requires the specific enthalpy [E], absolute humidity [HuAbs], and air pressure [AP] on 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 relationship of air pressure to 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

HX_TPHI can be used if a setpoint calculation is needed. For example, if TPHI_HX calculates the specific enthalpy [E] from the actual state of the air before an air humidifier, the desired absolute humidity [HuAbs] can be combined with the specific enthalpy [E] (from TPHI_HX) and the air pressure [AP] at the inputs for HX_TPHI to receive the setpoints for temperature [T] and relative humidity [HuRel].

Pins

Input	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…50.0 [g/kg] 0.000…0.050 [lb/lbda]
AP	Air pressure	Real	0.960 [bar] 28.35 [inHg] 0.000...4.000 [bar] 0.00...118.12 [inHg]

Input

Description

Data type

Default value
Value range

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…50.0 [g/kg]
0.000…0.050 [lb/lbda]

Air pressure

Real

0.960 [bar]
28.35 [inHg]

0.000...4.000 [bar]
0.00...118.12 [inHg]

Output	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 [%]
HuCod	Condensed water portion in saturated air Vapor condensed to water in air saturated with water vapor.	Real	2.0 [g/kg] 0.002 [lb/lbda] 0.0…20.0 [g/kg] 0.000…0.020 [lb/lbda]
EEf	Enthalpy effective (without condensate)	Real	40.0 [kJ/kg] 24.9 [Btu/lb] -20.0…100.0 [kJ/kg] -0.9…50.7 [lb/ft3]
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