Steam tables / Specific volume, saturated vapour
Specific volume of saturated steam against temperature
The room a kilogram of dry saturated steam takes up, 206.14 m³ at 0 °C down to 0.0031039 m³ at the critical point. Logarithmic axis. Computed from IAPWS-IF97.
Specific volume is how much room a kilogram of dry saturated steam takes up, and it collapses by four orders of magnitude across this chart. At 0 °C a kilogram fills 206.14 m³, which is a cube 5.9 metres on a side. At 100 °C it is 1.6719 m³, at 300 °C 0.021663 m³. That collapse is why a high pressure main carries the same duty in a fraction of the pipe, and why a vacuum steam system needs pipe the size of ductwork.
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.
| Saturation pressure | 1.0142 bar a · 0.0 psig |
| Latent heat of vaporisation | 2,256.5 kJ/kg |
| Saturated liquid enthalpy h_f | 419.1 kJ/kg |
| Saturated vapour enthalpy h_g | 2,675.6 kJ/kg |
| Temperature°C | Temperature°F | Pressurebar a | Pressurepsig | Specific volume, saturated vapourm³/kg | Specific volume, saturated vapourft³/lb |
|---|---|---|---|---|---|
| 0 | 32.0 | 0.006112 | -14.6 | 206.1 | 3,302 |
| 25 | 77.0 | 0.0317 | -14.2 | 43.34 | 694.3 |
| 50 | 122.0 | 0.1235 | -12.9 | 12.03 | 192.7 |
| 75 | 167.0 | 0.386 | -9.1 | 4.129 | 66.14 |
| 100 | 212.0 | 1.014 | 0.0 | 1.672 | 26.78 |
| 125 | 257.0 | 2.322 | 19.0 | 0.7701 | 12.34 |
| 150 | 302.0 | 4.761 | 54.4 | 0.3925 | 6.287 |
| 175 | 347.0 | 8.924 | 115 | 0.2166 | 3.47 |
| 200 | 392.0 | 15.55 | 211 | 0.1272 | 2.038 |
| 225 | 437.0 | 25.49 | 355 | 0.07841 | 1.256 |
| 250 | 482.0 | 39.76 | 562 | 0.05009 | 0.8023 |
| 275 | 527.0 | 59.46 | 848 | 0.03277 | 0.5249 |
| 300 | 572.0 | 85.88 | 1,231 | 0.02166 | 0.347 |
| 325 | 617.0 | 120.5 | 1,733 | 0.01419 | 0.2273 |
| 350 | 662.0 | 165.3 | 2,383 | 0.008801 | 0.141 |
| 373.946 | 705.1 | 220.6 | 3,185 | 0.003104 | 0.04972 |
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 the axis is logarithmic
The span is 206.14 m³/kg down to 0.0031039 m³/kg, which is five orders of magnitude. On a linear axis the entire useful range of a heating system would be one flat line along the bottom and the vacuum end would be the only thing visible. A log axis gives every decade the same amount of paper, which is the right choice for a quantity nobody thinks about additively.
What it sizes
Velocity in a steam main is mass flow times specific volume divided by area, so this curve is the pipe sizing chart with one step removed. Drop a header from 100 psig to 14.1 psig and the same kilograms per hour need about 3.7 times the pipe area to hold the same velocity. It is also the reason a vacuum steam system looks wrong to anybody who has only sized high pressure mains: at 40 °C a kilogram of steam fills 19.517 m³, and the pipe has to be big enough to let it move.
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
- Saturation pressure of water against temperature
- Latent heat of vaporisation of water against temperature
- Enthalpy of saturated water against temperature
- Enthalpy of dry saturated steam against temperature
← 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