# Work & Final Temperature in Piston Cylinder (Check my work)

by texas_better
Tags: check, cylinder, final, piston, temperature, work
 P: 1 If someone or a few people, just look this over and tell me if I'm right or if I did something wrong I'd be so grateful. I think it's all there but I'm not sure, there might be something off. 1. The problem statement, all variables and given/known data Air (which behaves like an ideal gas) undergoes adiabatic expansion in piston cylinder. T1 = 2000 K p1 = 4 MPa Undergoes adiabatic expansion to a volume that is v2 = 10v1. (v = specific vol) Find T2 (temperature of gas after expansion) and calculate adiabatic work, W, done. 2. Relevant equations 3. The attempt at a solution I found W = 863 kJ and I know this correct. The way I did it was by solving for v, specific volume, in pv = RT, and then putting V, volume, in terms of v and m, mass, like $V = vm$. I then used the polytropic process and the V1's cancel when you sub V2=10V1. I end up w/ 863m (kJ). Then used Q - W = E2-E1. Q is 0 (adiabatic) Then, -W = E2-E1 -W = U2-U1 only internal energy -W = m(u2-u1) where u = specific enthalpy -W = mcv(u2-u1) where cv=0.718 kJ/kg*k for air -W = mcv(T2-T1) In the final step I substituted W = 863m (kJ), the cv value, T1 = 2000 K, and solved for T2 to get 797k. Is this legit? Thanks for any help.

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