# Latent heat of vaporization Water thermodynamic

1. Oct 3, 2009

### firavia

Latent heat of vaporization "Water" thermodynamic

-first of all I want to know if the "latent heat of vaporiasation " of water is related to the initial pressure of water ?

-If LHV of water is variable with the variation of pressure , how can we calculate the heat needed to vaporise a certain mass of water inside a container , cause as we know while heating the container and water start to evaporate the pressure inside the container will increase gradually , so the heat needed to complete the vaporisation must be increased cause the LHV has changed with the change of pressure inside the container , please help

2. Oct 3, 2009

### turbo

Re: Latent heat of vaporization "Water" thermodynamic

You should look up "steam table" as a beginning. This stuff is quite well-understood, since it was the foundation for much of the industrial revolution.

3. Oct 3, 2009

### Q_Goest

Re: Latent heat of vaporization "Water" thermodynamic

Yes, Ufg (and Hfg) decrease with increasing P.

You can solve the problem simply applying the first law of thermo. Easiest way IMHO is to apply numerical methods using a computerized data base. This same type of problem comes up quite a bit in the industrical gas business for cryogenic liquids.

4. Oct 6, 2009

5. Oct 9, 2009

### ank_gl

Re: Latent heat of vaporization "Water" thermodynamic

What do you mean by "initial" pressure of water?

I am having trouble in visualizing the system you described. If its a closed system & is being heated, pressure in the container remains same while vaporization, and LHV is constant for a pressure.