Thermodynamics Flashcards

1
Q

First law of thermodynamics energy balance

A

H1 + KE1 + PE1 = H2 + KE2 + PE2 + q + W

Total energy in = Total energy out

-q = heat loss
-W = Turbine work
-H = enthalpy

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2
Q

What is enthalpy?

A

-Total heat and heat content of a substance
-Sum of internal energy and flow work

-h = u + Pv

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3
Q

Ideal gas formula

A

PV = mRT

-P = absolute pressure
-V = volume
-m = mass
-R = gas constant
-T = absolute temperature

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4
Q

Any process involving ideal gas (PVT)

A

(P1V1/T1) = (P2V2/T2) = mR

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5
Q

Any process involving ideal gas (U)

A

U2 - U1 = mCv(T2-T1)

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6
Q

Any process involving ideal gas (H)

A

H2 - H1 = mCp(T2-T1)

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7
Q

Any process involving ideal gas (S)

A

S2 - S1 = mCpln(T2/T1) - mRln(P2/P1)

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8
Q

Reversible process

A

No friction loss

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9
Q

Adiabatic process

A

No heat loss, no heat gain, completely insulated system

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10
Q

Adiabatic throttling process

A

-Constant enthalpy or isenthalpic
-h2=h1 and t2=t1

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11
Q

Particular value n for isobaric process

A

n = 0

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12
Q

Particular value n for isothermal process

A

n = 1

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13
Q

Particular value n for isentropic (adiabatic) process

A

n = k

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14
Q

Particular value n for polytropic process

A

n > 1

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15
Q

Particular value n for isometric or isochoric process

A

n = ∞

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16
Q

Definition of subcooled liquid

A

Liquid whose temperature is lower than the sat. temperature at the given pressure

17
Q

Relationship between vf , vg, and vfg

A

vfg = vg - vf

  • where v = specific volume
  • applies to u, h, and s
18
Q

Quality or dryness factor x

A

x = mv/(mv+mL) = mv/mT
-mv=mass of vapor
-mL=mass of liquid
-mT=total mass of mixture

19
Q

Wetness given dryness factor

A

Wetness = 1-x

20
Q

Properties of a mixture (v,h,u,s)

A

v = vf + x vfg

21
Q

Formula for specific heat at constant pressure, cp

A

Rk/ (k-1)
-R = gas constant
-k = specific heat ratio

22
Q

Formula for specific heat at constant volume, cv

A

R/(k-1)

23
Q

Pressure and temperature relation for ideal gas (all processes)

A

T2/T1 = (P2/P1) ^ ( n-1 / n )
-n = particular value

24
Q

Temperature and volume relation for ideal gas (all processes)

A

T2/T1 = (V1/V2) ^ (n-1)

25
Q

Entropy change under constant pressure

A

mCpln(T2/T1)

26
Q

Entropy change under constant volume

A

mCvln(T2/T1)

27
Q

Entropy change under constant temperature

A

mRln(V2/V1)