Hot Water

[Awlthumbs]

Can someone please help me. I would like to find out the formula to work out the energy required to convert 1 litre of water to steam for the following:
(a) At atmoshphere
(b) Under pressure eg 300kPa

[Robert Stephen MortonParticipant]

Johnws. The S.I unit for heat is the Joule (J) it takes 4,186 J of energy to raise the temp of 1 litre (= 1 kg) of water through 1degree C this is called the specific heat capacity of water.
Heat energy =mass specific heat capacity temp rise
H.e (kg) = mass (kg)x 4.186 (t2 -t1)deg c

Johnws, you need to know the initial temp to calculate.

the temp dif in a pressure situation is aprox 1deg f / 550ft

[Robert Stephen MortonParticipant]

Johnws. The S.I unit for heat is the Joule (J) it takes 4,186 J of energy to raise the temp of 1 litre (= 1 kg) of water through 1degree C this is called the specific heat capacity of water.
Heat energy =mass specific heat capacity temp rise
H.e (kg) = mass (kg)x 4.186 (t2 -t1)deg c

Johnws, you need to know the initial temp to calculate.

the temp dif in a pressure situation is aprox 1deg f / 550ft

[johnwsParticipant]

Thanks Robert for the reply, but this answers part of the question as this formula only takes the temperature to boiling point. Given that once the temperature is raised to 100 deg C (at atmospheric pressure) any additional energy will not raise the temperature further but will only convert the water to steam. Therefore how much extra energy is now required to convert this water to steam.

Look forward to your reply

[GuestParticipant]

The theoretical value for the latent heat of vaprization of water is 2.26 106 J/kg.
http://wug.physics.uiuc.edu/courses/phys113/summer01/Discussions/html/wk6/sol6_2.htm

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