vapour to condensation

paul_pearson

I have read the rules and this IS not homework.....i work in a factory

Hi

I have Vapour at 52 degrees from a tank (-87.7kPa) going to a Condensor (heat exchange) under vacuum pressure (-87.7kPa).....The Condensor uses water on 1 side to condense vapour on the other side....
1. What temperature does the water need to be to condense the Vapour
2. The vapour produced is 2500kg/hr
3. If evaporating 2500kg/hr of water how much vapour would that produce....would it be 2500kg of Vapour but in a much larger area?

Thank you

Paul

SteamKing

1. Its not temperature that controls condensation, but the removal by the condenser of the latent heat of vaporization of the vapor.

etudiant

Condensing vapor, as SteamKing says, requires removing the latent heat of vaporization. That is 2260 kJ/kg, about 580 kcal/kg, so the cooling water has to absorb 2500*580kcal/hr. Assuming the cooling water temperature is raised by 10 degrees C in the heat exchanger and knowing that it takes 1 kcal to raise 1 kg of water 1 degree C, the flow through the heat exchanger is 2500x58kg/hr, almost 150,000kg/hr, about 150 cubic meters/hr, clearly an industrial scale installation.
The water will need to be colder than 58 degrees C for the heat exchanger to work well, but most natural sources are below 25 degrees C, which should give adequate cooling. Higher water temperatures will lower the condensation rate possible in the heat exchanger, reaching 0 at 58 degrees C.
Evaporating water does not change the weight, just the volume. Pure steam is about 1600 times the volume of water at 1 atmosphere.