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Old Sep 4th 2019, 05:25 AM   #1
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Question Evaporating Water with a Boiler Type Vessel

I am attempting to evaporate water to the atmosphere with a boiler type vessel. Normal operating pressure of the vessel would be 5 psig. How much water could potentially be evaporated? Also, what issues come to mind with this concept?
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Old Sep 5th 2019, 04:06 AM   #2
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If you are evaporating to Atmosphere, there is no limit to the amount of water that could be evaporated.
However if you are limited to 5 psi over atmospheric, there will be a limit to how fast you can evaporate the water.

The actual limit will depend on lots of details you have not supplied;

The energy rate available from your source of heat
The amount of Water,
The size of your Boiler,
The size of the Vent from your Boiler to Atmosphere,
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Old Sep 6th 2019, 06:08 AM   #3
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You can estimate the rate of evaporation using the equation for latent heat transfer:

$\displaystyle \dot{m} = \frac{\dot{Q}}{h_{liq-vap}}$

where m is the evaporation rate (in kg/s), Q is the rated power output of your boiler (in W) and $\displaystyle h_{liq-vap}$ is the specific enthalpy of liquid-to-vapour phase change of water.

At room temperature and pressure, $\displaystyle h_{liq-vap} = 2265 $ kJ/kg, but it's actually a function of temperature and pressure, so it's probably a little bit lower than this. You should recalculate this constant at the boiling point of water at that pressure (which I think is about 108 deg. C at 134 kPa).
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