(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A possible ideal-gas cycle operates as follows:

(i) from an initial state (p1,V1) the gas is cooled at constant pressure to (p1,V2);

(ii) the gas is heated at constant volume to (p2,V2);

(iii) the gas expands adiabatically back to (p1,V1).

Assuming constant heat capacities, show that the thermal eficiency is:

1-ɣ[((V1/V2) - 1) / ((p2/p1) -1)]

2. Relevant equations

I used first law of thermal dynamics, n = W/Qh, differential forms of Cv and Cp.

change in energy for the complete cycle = 0, therefor W = Qh + Ql.

3. The attempt at a solution

Using efficiency = W / heat absorbed.

I attempted to find the W and Q of the 3 processes separately.

I was using for Isobaric: dW = -Pdv but im pretty sure this is incorrect because no where does it state it is a reversible process. But the book for the class only shows reversible processes for examples and does not actually show a isobaric or isochoric process in any example.

I tried using the differential form of Cv and Cp and rearranging them to find dQ, but failed.

I have used 4 or 5 sheets of paper, trying every way i could think of to work this problem out. I know im missing something and if someone could just point me in the right direction I would gladly appreciate it and work out the problem on my own.

Thanks

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Efficiency of an ideal-gas cycle.

**Physics Forums | Science Articles, Homework Help, Discussion**