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## Homework Statement

Steam in a piston-cylinder assembly undergoes a polytropic process. Kinetic and potential energy effects are negligible. For the process, determine the work and heat transfer, each in Btu per lb of steam.

p

_{1}= 100 lbf/in

^{2}

p

_{2}= 40 lbf/in

^{2}

v

_{1}= 4.934 ft

^{3}/lb

v

_{2}= 11.04 ft

^{3}/lb

u

_{1}= 1136.2 Btu/lb

u

_{2}= 1124.2 Btu/lb

## Homework Equations

ΔE = Q - W

W = ∫

_{v1}

^{v2}pdV

## The Attempt at a Solution

Since the process is polytropic, PV

^{n}= constant = p

_{1}V

_{1}

^{n}= p

_{2}V

_{2}

^{n}

Thus, W = ∫

_{v1}

^{v2}(constant/V

^{n})dV = (p

_{2}V

_{2}- p

_{1}V

_{1})/(1-n)

I used the relation p

_{1}V

_{1}

^{n}= p

_{2}V

_{2}

^{n}to find n, which gives me n = 1.14

Then, my plan is to plug the numbers into my integrated work function, but I am extremely confused on the units of this and I'm not really sure if I'm even working in the right direction. Basically I've gotten stuck at this point. Any help would be much appreciated.