Steam Tables

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Steam tables

Steam tables indicate properties of steam at various pressures and temperatures (depending upon how the table is designed). The properties listed are usually:

  • Pressure.
  • Temperature.
  • Specific volume of dry saturated steam (Vg).
  • Enthalpy of water at saturation temperature (hf).
  • Enthalpy of vaporisation (hfg).
  • Enthalpy of dry saturated steam (hg).

A simplified steam table is shown below.

Gauge Pressure
(psig)

Temperature
(oF)

vg

Specific Volume
(cu ft/lb)

Enthalpy

hf

Saturated Water
(Btu/lb)

hfg

Latent Heat of Vaporisation
(Btu/lb)

hg

Dry Saturated Steam
(Btu/lb)

0

212

26.7

180

970

1150

10

239

16.6

208

953

1160

20

259

11.8

227

938

1166

30

274

9.46

243

929

1174

40

287

7.82

256

919

1176

50

298

6.68

267

912

1179

60

307

5.84

277

906

1183

70

316

5.18

286

898

1184

80

324

4.67

294

894

1185

90

332

4.25

302

886

1189

100

339

3.89

309

879

1189

Example Steam Table

The table columns can be read as:

  • Pressure – the gauge pressure at which the steam table values occur i.e. the pressure at which the experiment to measure the other corresponding values was made.
  • Temperature – the temperature at which the water’s saturation point is reached i.e. the boiling point.
  • Specific volume of dry saturated steam (Vg) – the volume occupied by 1 lb (imperial) or 1 kg (metric) of dry saturated steam.
  • Enthalpy of water at saturation temperature (hf) – the amount of sensible heat required to raise 1 lb or 1 kg of water from its freezing point to its saturation temperature (boiling point).  
  • Latent heat of vaporisation (hfg) – the amount of latent heat required to turn 1 lb or 1 kg of water at saturation temperature into 1 lb or 1 kg of dry saturated steam. 
  • Enthalpy of dry saturated steam (hg) – the total amount of heat required to turn 1 lb or 1 kg of water at its freezing point into 1 kg of dry saturated steam.

Or, to take a simplistic view:

  • Pressure – pressure at which the experiment was conducted. 
  • Temperature – boiling point at the given pressure.
  • Specific volume of dry saturated steam (Vg) – volume of dry saturated steam at the given pressure.
  • Enthalpy of water at saturation temperature (hf) – energy required to heat the water from its freezing point to its boiling point.  
  • Latent heat of vaporisation (hfg) – energy required to evaporate the saturated water into dry steam. 
  • Enthalpy of dry saturated steam (hg) – energy required to heat-up and evaporate the water into dry steam.

Example

Sensible heat is applied to water to raise its temperature from its freezing point to its boiling point, this is the value hf. Latent heat is then added to change the state of the saturated water into dry saturated steam, this is the value hfg.

Adding the values of hf and hfg, gives the total amount of heat required to take a given mass of water from its freezing point to its boiling point, then to convert that saturated water into dry saturated steam. The equation for this entire process is:

 

hg = hf + hfg

 

 

Additional Resources

https://en.wikipedia.org/?title=Steam_table&redirect=no

https://www.tlv.com/global/US/steam-theory/how-to-read-a-steam-table.html