Why Are Carnot Cycle Calculations So Confusing?

[Ulyaoth]

Nevermind for now, just redid the whole thing and saw I made a stupid little mistake in computing the first volumes that messed everything else up.

A Carnot engineer operating with a perfect gas between 800C and 25C has an operating pressure range between 20kPa and 6000kPa. Determine the work of the cycle, heat added, heat rejected, and efficiency is the gas has physical properties equivelant to those of air.

The textbook says that Wk12=Q12, and that the equation for such should be mRT1 ln(V2/V1) but first of all, using the various ways it gives for coming up with Volume come up with different numbers, any of these numbers used for finding the work come up completely off from the answer the book gives of 271kJ/kg.

I just have no idea what to do because my textbook is absolutely useless once again.

So far I've come up with V1 being 4276m^3
V2=353.5m^3
V3=51.325m^3
and V4=172.4m^3
All using V=mRT/p, or V(tl/th)^1/k-1

But none of these numbers are working right and if I get the pressures and then get the volumes with that then it comes out different, besides shouldn't v4 be only lower than 1?

 

[Valkarie]

Anyways, if someone could just point out what I'm doing wrong or explain what I need to do that would be great.