work done by a steady flow process,
and work done in a non–flow process,
1. Constant Volume Process; W1-2 = V(P1 – P2
Steady flow equation
dq = du = dh + d (ke) + d (pv)
Now h = a + pr
Differentiating
dh = du + dtper
= du = pdv = vdp
From First Law of Thermodynamics for a closed system.
2. Constant Pressure process; W1-2 = V(P1 – P2) = 0
3. Constant temperature process;
4. Adiabatic Process; W1-2 = y(P1V1 – P2V2)/(y – 1)
5. Polytropic process; W1-2 = n(P1V1 – P2V2)/( n – 1)
Non – Flow Process
6. Throttling Process The expansion of a gas through an orifice or partly opened valve is called throttling.
The throttling process is a constant enthalpy process. If the readings of pressure and temperature of Joule Thompson porous plug experiment are ploted,
h1 = h2 = h3 = h4 = h
The slope of this constant enthalpy curve is called Joule Thompson coefficient.
For a perfect gas, p = 0.
