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Finding Water content in air in kg/kg given relative humidity & temp

Not being from a sciencey background I'm having a problem finding the amount of water vapour in air (in kg/kg) at a certain relative humidity and temperature. The composition of dry air is pretty much standard but I need an expression for the composition at a certain relative humidity. What I'm planning to do once I can determine the components for a certain RH and temp is determine how RH affects combustion efficiency (I can do this for dry air and excess air but need help with RH)

I can get the vapour density of the water from RH = (vapour density)/(saturation vapour density) but where to from here, if this is the right starting point at all? I think I should be looking at the partial pressures of the components of air but I'm not too sure. Any pointers would be much appreciated.

Reply to
Titan
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Search for mass of water in air per RH

This is the first pointer I came to.

Scroll down for a graph of mass of water per air volume versus temperature for saturated air. You can work out the mass of air from its volume, and you can scale the mass of water linearly from the RH at a given temperature. Remember that air grows less dense with increasing humidity though.

Brian Whatcott Altus OK

Reply to
Brian Whatcott

You are right about the pressures, b/c in this case you are looking at combustion (large change in pressures). Normally you would use a psych chart:

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You can still do this but, you need to use the correct chart given your pressure.

Reply to
istone76

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