- #1

MacLaddy

Gold Member

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## Homework Statement

I have a problem that I've mostly solved using Ideal-gas specific heats for Oxygen. It has the form [itex]C_p = a + bT + cT^2 + dT^3[/itex]

I am supposed to give the answer in English units of [itex]\frac{Btu}{lbm}[/itex], but I am having some difficulties in my conversion.

## Homework Equations

[itex]C_p = a + bT + cT^2 + dT^3[/itex]

## The Attempt at a Solution

After integrating to solve above I have the answer of [itex]5442.3\frac{Btu}{lbmol*R}[/itex]. These units are given to me via my property tables booklet.

In trying to convert [itex]5442.3\frac{Btu}{lbmol*R}[/itex] to [itex]\frac{Btu}{lbm}[/itex] I am using the fact that Oxygen has a molar mass of [itex]31.999\frac{lbm}{lbmol}[/itex].

Using this conversion factor I get [itex]\frac{5442.3\frac{Btu}{lbmol*R}}{31.999\frac{lbm}{lbmol}}=170.1\frac{Btu}{lbm*R}[/itex]

I am getting the extra factor of Rankine in the denominator. My instructor has a solution video she's presented, and she doesn't even use the R in the original units from the property tables booklet, but it clearly shows it.

Any clarification would be appreciated.

Thanks,

Mac