Thermodynamics Flashcards
Quality
fraction of total mass that is vapor
x=m_g/(m_g+m_f)
Specific Enthalpy
h=u+pv
h=hf+xhfg
Molar Enthalpy
H=mh
Internal Energy
U=H-pV
u=uf+xufg
delta u = c_v*delta T
Units: kj/kg
Gibbs Function
g=h-Ts=u+pv-Ts
Heat Capacity (Specific Heat)
cv - Constant Volume
cp - Constant Pressure
Q=mc(T2-T1)
Q=heat energy
First law of thermodynamics
Q=delta U + W
conservation of energy for open systems
Universal Constant: R
8314 m^3*Pa/(kmol*k)
Ideal Gases undergoing Isentropic Processes
p_2/p_1=(v_1/v_2)^k
T_2/T_1=(v_1/v_2)^(k-1)
T_2/T_1=(p_2/p_1)^((k-1)/k)
k=c_p/c_v
Entropy
delta s = integral ds = integral dq/T
adiabatic process
A process in which no energy crosses the system boundary
throttling process
An adiabatic process in which there is no change in enthalpy, but for which there is a significant pressure drop
isochoric or isometric process
constant volume process
W=0
T/p=constant
polytropic process
A process which obeys the polytropic equation of state. (pv^n) Gases always constitute the system in polytropic processes.
pv^n=constant
W=(p2v2-p1v1)/(1-n) - closed system
W=n(p2v2-p1v1)/(1-n) - closed system
isentropic
pv^k=constant
W=(p2v2-p1v1)/(1-k)
=R(T2-T1)/(1-k)
=(RT/(k-1))*(1-(p2/p1)^(k-1)/k
isothermal
pv=constant
W=RTln(v2/v1)=RTln(p1/p2) - closed system
W=RTln(v2/v1)=RTln(p1/p2) - open system
Work
First assume some combination of Pdv