Calc Resultant Temp/Pres from 2 air streams

[totalfit]

Ho do I calculate the resultant temperature and pressure given two air streams at two different pressures/temps?
ie Stream 1(Temp = 1180degF, +2"of H20, 300000lbs.hr)Stream 2(Temp = 284degF, +3"of H20, 191000 lbs.hr)
Area ratios accurate?

 

[hacksaw]

you have to look at the heat capacities. common calculation.

 

[pmureiko]

The mean specific heat for the hot air is about 0.25 Btu/lb-oF and the cold air is about 0.245 Btu/lb-oF.

The pressures are very close to atmospheric and will have negligible affect on the result.

 

[EGT01]

Depends on how accurate you want to be.

For more accuracy, perform a heat balance calculation for mixing the 2 streams. The resulting equation is
dQ1 = dQ2
dQ1 = m1 * Cp1(mean) * (1180 - x)
dQ2 = m2 * Cp2(mean) * (x - 284)
Then solve for "x".

The problem is knowing Cp(mean) which requires some iteration. Guess "x", determine Cp(mean) for each stream, solve for "x" and compare to your guess.

As a starting point, you could just assume
(300000/491000)*1180 + (191000/491000)*284 = 831.5F

I think you will find your final answer won't be far from this.

As for the resultant pressure, based on giving mass flow rates, I assume you are mixing in a pipeline. The resultant pressure will be a function of the piping system hydraulics with pressure after mixing less than +2"H2O, otherwise you can't mix.