9 replies to this topic

[cheminst]

Can anyone please explain how to calculate the enthalpy change when water is evaporating below the boiling point? e.g. 50 Celsius at 1 atm.

 

Any reference book or webpage link?

[PingPong]

Use a Steam Table.

[cheminst]

Use a Steam Table.

Actually in a steam table there are only data for saturated steam and superheated steam. The data I want are the enthalpy change of vaporization of water at 1 atm below boiling point (100 Celsius) e.g 30, 40, 50, 60 Celsius.  This is neither saturated steam nor superheated steam.

[PingPong]

At low pressure all gases behave like (nearly) ideal gases and therefor impact of pressure on enthalpy is negligible.

[PhilippM]

 

This is neither saturated steam nor superheated steam.

 

 

What else is the steam supposed to be?

[cheminst]

At low pressure all gases behave like (nearly) ideal gases and therefor impact of pressure on enthalpy is negligible.

Thanks for the clarification.

[cheminst]

 

 

This is neither saturated steam nor superheated steam.

 

 

What else is the steam supposed to be?

 

Actually I meant the steam for which only the data are given in steam tables

[PingPong]

At 50 ^oC water has a vapor pressure of 0.123 bar, so saturated steam at 50 ^oC has a partial pressure of 0.123 bar.

 

In air (or whatever gas) at 1 atm the steam partial pressure at 50 ^oC is only 0.123 bar and the air partial pressure is 0.89 bar.

 

The enthalpy of pure steam at 50 ^oC and 0.123 bar total pressure will be practically the same as the enthalpy of steam at 50 ^oC in air at a total pressure of 1 atm.

[breizh]

https://www4.eere.en..._tool/propSteam

 

Let you try he calculator above , just pay attention to the inputs  (F,PSI g) .

good luck

Breizh

[cheminst]

Found the data

 

https://www4.eere.en..._tool/propSteam

 

Let you try he calculator above , just pay attention to the inputs  (F,PSI g) .

good luck

Breizh

Thanks for the link. I found NIST data through this link.

https://webbook.nist...Pa*s&STUnit=N/m