[john251200 (OP)]

Hey all.
The combustion of one m3 of methane releases approx 1.61 kg of water vapour as far as i have found. In condensing heat exchangers, depending on the temperature of the heat exchanger coils, some of this water vapour will condense before leaving the boiler giving off latent heat as "free" useful heat to the coils.

I'd like to plot a graph with the temperature of the coil or flue gas vs how much water vapour will have condensed, ie in 5 degree c increments from 25 to 100 flue gas temp vs volume/mass of condensed water in the boiler for each m3 of methane burned.

How would I go about calculating the approximate condensed water volume at each flue gas temperature?

Thanks for any input

[Bored chemist]

You can calculate how much stays in the flue gas from data like this
https://www.engineeringtoolbox.com/maximum-moisture-content-air-d_1403.html

Whatever water is present in excess of that will condense.
The fact that it's flue gas (not air) won't matter
You might need to make some allowance for the humidity of the incoming air.

[john251200 (OP)]

Thanks,
So the mass of water that air can carry is the same as flue gas?

[Bored chemist]

At a given temperature, and on a mass of water per volume of gas basis, yes.