# Thermodynamic cycle

1. Oct 10, 2005

### kdinser

Sorry about the double post, I had technical difficulties that I was working on and the title of my orginal post got screwed up.

I'm having problems getting started on this one.

A gas undergoes a thermodynamic cycle consisting of 3 processes

process 1-2 compression with pressure(p)*volume(V) = constant, from
$$p_{1} = 1 bar$$
$$V_{1} = 1.6m^3$$
to
$$p_{2} = ?$$
$$V_{1} = .2m^3$$

$$U_{2}-U_{1}=0$$

process 2-3
Constant pressure to $$V_{3}=V_{1}$$

process 3-1
Constant Volume, $$U_{1}-U_{3} = -3549kJ$$

There are no significant changes in kinetic or potential energy.
Determine the heat transfer and work for process 2-3 in kJ.

I don't have any problems finding$$p_{2}$$ or the work needed to compress the gas, but I'm not really sure where to go from there.

$$p_2=\frac{p_1V_1}{V_2}$$

$$W=\int p dV$$

When I work these out, I end up with 333kJ for W and 8 bar for p2.

If someone could give me a quick push in the right direction, that would be great.

2. Oct 10, 2005

### Andrew Mason

The work done between 2-3 is just $P_2\Delta V = P_2(V_3-V_2) = P_2(7*V_2)$

The change in internal energy is $U_3-U_2 = U_3-U_1$, since $U_2=U_1$

Use $\Delta Q = \Delta U + W$ to find the energy (heat) flow into the system.

AM

Last edited: Oct 11, 2005