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Steam tables / Saturated liquid enthalpy h_f

Enthalpy of saturated water against temperature

The heat in a kilogram of saturated water, measured from zero at the triple point, 0.01 °C. This is the enthalpy of condensate at any trap on the system. Computed from IAPWS-IF97.

hf is the sensible heat in a kilogram of saturated water, measured from the triple point where IAPWS-IF97 sets it to exactly zero. It is the enthalpy of the condensate leaving every trap on the system, so it is half of any flash calculation and the reason hot condensate is worth returning. It climbs the whole way: 419.1 kJ/kg at 100 °C, 1,344.8 kJ/kg at 300 °C, and it keeps climbing until it meets the vapour branch at the critical point.

Arrive here from a chart on the steam tables page and the temperature you dialled in comes with you, marked on the curve and bolded in the table that prints beside it. The sheet is then about one operating point rather than about water in general.

Table units — bar, °C, m³/kg, kJ/kg. Both columns of pressure, absolute and gauge, either way.
Saturated liquid enthalpy h_f kJ/kg
Enthalpy of saturated water in kilojoules per kilogram against temperature, climbing from zero at 0 °C to the critical point0200400600800100012001400160018002000020406080100120140160180200220240260280300320340360Saturation temperature (°C)Saturated liquid enthalpy h_f (kJ/kg)
The rest of the state at 100 °C (default)
Saturation pressure1.0142 bar a · 0.0 psig
Latent heat of vaporisation2,256.5 kJ/kg
Specific volume, saturated vapour1.672 m³/kg
Saturated vapour enthalpy h_g2,675.6 kJ/kg
Saturated liquid enthalpy h_f along the whole saturation line
Temperature°CTemperature°FPressurebar aPressurepsigSaturated liquid enthalpy h_fkJ/kgSaturated liquid enthalpy h_fBTU/lb
032.00.006112-14.6-0.0-0.0
2577.00.0317-14.2104.845.1
50122.00.1235-12.9209.390.0
75167.00.386-9.1314.0135.0
100212.01.0140.0419.1180.2
125257.02.32219.0525.1225.7
150302.04.76154.4632.3271.8
175347.08.924115741.2318.6
200392.015.55211852.4366.5
225437.025.49355966.8415.7
250482.039.765621,085.7466.8
275527.059.468481,210.7520.5
300572.085.881,2311,344.8578.1
325617.0120.51,7331,493.4642.0
350662.0165.32,3831,670.9718.3
373.946705.1220.63,1852,087.2897.4

Every row is a call into IAPWS-IF97 made when this page was built, not a transcription. Gauge pressure is absolute minus one standard atmosphere, 101.325 kPa, so it is negative everywhere below 99.97 °C, which is where water actually boils at one atmosphere, and a real barometer is never exactly that anyway.

Learning zone

Why it starts at zero, and why that is a convention

IAPWS-IF97 sets internal energy and entropy to exactly zero for saturated liquid at the TRIPLE POINT, 0.01 °C, and everything else is measured from there. The left edge of this chart is 0 °C, a hundredth of a degree BELOW that reference, which is why hf reads -0.0416 kJ/kg there rather than zero. There is nothing wrong with a negative enthalpy: no thermodynamic table reports an absolute energy, because no experiment measures one. Only differences are physical, and every calculation done with these numbers is a difference.

Where it gets used

Flash steam. Condensate leaving a trap at 419.1 kJ/kg cannot stay liquid when it is let down to a pressure whose hf is lower, so the surplus boils off part of the flow. The flash steam solver takes hf at both pressures and hfg at the lower one and does exactly that subtraction. The practical warning is never to mix tables: a steam table on a different reference gives the same differences and different absolute numbers, and a calculation that takes hf from one and hg from another is quietly wrong by the offset between them.

IAPWS R7-97(2012), regions 1 to 5 implemented in full · saturation line from 0 °C to 373.946 °C · computed at page build, never transcribed

The other curves on this line

← Steam tables: every curve, both full tables and the saturated and superheated panels

The saturation dome, the Mollier h–s chart and the T–s diagram