Thermodynamics Flashcards
First law of thermodynamics energy balance
H1 + KE1 + PE1 = H2 + KE2 + PE2 + q + W
Total energy in = Total energy out
-q = heat loss
-W = Turbine work
-H = enthalpy
What is enthalpy?
-Total heat and heat content of a substance
-Sum of internal energy and flow work
-h = u + Pv
Ideal gas formula
PV = mRT
-P = absolute pressure
-V = volume
-m = mass
-R = gas constant
-T = absolute temperature
Any process involving ideal gas (PVT)
(P1V1/T1) = (P2V2/T2) = mR
Any process involving ideal gas (U)
U2 - U1 = mCv(T2-T1)
Any process involving ideal gas (H)
H2 - H1 = mCp(T2-T1)
Any process involving ideal gas (S)
S2 - S1 = mCpln(T2/T1) - mRln(P2/P1)
Reversible process
No friction loss
Adiabatic process
No heat loss, no heat gain, completely insulated system
Adiabatic throttling process
-Constant enthalpy or isenthalpic
-h2=h1 and t2=t1
Particular value n for isobaric process
n = 0
Particular value n for isothermal process
n = 1
Particular value n for isentropic (adiabatic) process
n = k
Particular value n for polytropic process
n > 1
Particular value n for isometric or isochoric process
n = ∞
Definition of subcooled liquid
Liquid whose temperature is lower than the sat. temperature at the given pressure
Relationship between vf , vg, and vfg
vfg = vg - vf
- where v = specific volume
- applies to u, h, and s
Quality or dryness factor x
x = mv/(mv+mL) = mv/mT
-mv=mass of vapor
-mL=mass of liquid
-mT=total mass of mixture
Wetness given dryness factor
Wetness = 1-x
Properties of a mixture (v,h,u,s)
v = vf + x vfg
Formula for specific heat at constant pressure, cp
Rk/ (k-1)
-R = gas constant
-k = specific heat ratio
Formula for specific heat at constant volume, cv
R/(k-1)
Pressure and temperature relation for ideal gas (all processes)
T2/T1 = (P2/P1) ^ ( n-1 / n )
-n = particular value
Temperature and volume relation for ideal gas (all processes)
T2/T1 = (V1/V2) ^ (n-1)
Entropy change under constant pressure
mCpln(T2/T1)
Entropy change under constant volume
mCvln(T2/T1)
Entropy change under constant temperature
mRln(V2/V1)
