Gibbs Equations

Tds = du + Pdv

Tds = dh - vdP

ΔS = 

Q/T

isentropic process

constant entropy; ΔS = 0; internally reversible and adiabatic

isentropic process of ideal gas assumptions: 

1. ideal gas

2. isentropic process

3. constant specific heat

reversible work equation

vdP or v(P₂-P₁)

isentropic efficiency, turbines

w_a/w_s = (h₁ - h_2s)/(h₁ - h_2a)

w_s/w_a = (h_2s - h₁)/(h_2a - h₁)

isentropic efficiency, pump

w_s/w_a= v(P₂ − P₁)/(h_2a − h)

compression ration, r = 

v_max/v_min = v₁ / v₂

1) No friction at surfaces in the working fluid

2) All expansion and compression processes occur in a quasi-equilibrium manner

3) All piping is insulated, so heat is only lost at heat exchangers

1. The working fluid is air which works in a continuous loop and always acts as an ideal gas

2. All process are internally reversible

3. The combustion process is replaced by a heat-addition process from an external source.

4. The exhaust process is replaced by a heat rejection process that restores the working fluid to its original state.

5. It is also commonly assumed that the specific heats of the air are constant at the 25ºC value (Cold-air standard assumption.)

= w_net/q_in

= 1 − q_out/q_in

= w_net/q_in

= 1 − q_out/q_in