Thermo, set 3
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enthalpy
 a convenient grouping of the internal energy, pressure, and volume
 H = U + PV or h = u + pv [kJ/kg]
 Heat flow for process at constant pressure
 Q = change in enthalpy

saturation pressure
pressure at which the liquid and vapor phases are in equilibrium at given temp

saturation temperature
the temperature at which the liquid and vapor phases are in equilibrium at given pressure

enthalpy of vaporization
(latent heat of vaporization), h_fg  the amount of energy needed to vaporize a unit of mass of saturated liquid at a given temp /pressure

moisture
1  x, where x is quality x, or mg/mg+mf

Lever Rule
 x = (yyf)/yfg
 where y may be replaced with v, u, h, or s, and x is the mass of saturated vapor divided by total mass

superheated
given tempreature is greater than the saturation temp for given pressure

compresed liquid
when the pressure is greater than the saturation presure at a given temp

How to choose the right table
Compare the known state properties to the properties in the saturation region

compressed liquid region
v < vf

saturation region
vf < v < vg

superheated region
vg < v

equations of state
relationship between the state variables, temperature, pressure, and specific volume

ideal gas law
 Pv = RT
 Used when 1) pressure is small compared to critical pressure, 2) Temp is twice critical temp and pressure is less than 10 times critical pressure

Gas constant R
 R = Ru/M
 Ru is universal gas constant

mass
m = NM, the number of moles times the molar mass

Combined gas law
 Ideal gas for a fixed mass  m1 = m2, or
 PV/RT (1) = PV/RT (2)

1st Law of Thermo
 Expression of the conservation of energy, energy can cross boundary of closed system as work or heat
 dU = d q  pdV
 If energy transfer is due to temp. diff, it's heat, otherwise it's work.

State function
of energy  value depends on final and initial states, not on internal energy used

Chemical potential
proportionality constant m; change in internal energy is proportional to the number of particles dn added to the styem

Combined 1st and 2nd laws
dU = TdS – PdV + mdn

Kelvin Statement
It is not possible for the absorption of heat from a reservoir to complete convert to work

Entropy
 measure of dispersal of energy (molecular disorder)
 Nonconserved property; as entropy increases, it increases entropy of universe
 Increases as DOF increases

Isentropic
 Entropy does not change (either by heat transfer or irreversibilities)
 Or, reversible adiabatic process

Reversible Process
ability to run a process back and forth infinitely without losses (i.e. perfect pendulum, mass on string, etc.)

Irreversible Process
 i.e. dropping clay, hammering a nail, breaking glass
 Sources; friction, pressure, voltage, temp, and concentration drops

adiabatic
 no heat is gained or lost in a system
 q=0

Engineering devices
work best when isentropic and irreversibilities are eliminated

Disorder
naturally increases, and natural processor proceed spontaneously to order

2nd Law of Thermo
 entropy of isolated system, i.e universe, increases in any spontaneous change
 deltaS_{tot}>0
 Entropy of universe continuously changing
 irreversible process of transferring heat from hot to cold body

spontaneous
 process that occurs without ongoing outside intervention
 i.e. ice melting at room temperature, expansion of gas in space

Molecular motion
 Translational  entire molecule moves
 Vibrational  within a molecule
 Rotational  'spinning'
 motions 'shut down' as temp decreases > reach perfect order

Change in Standard Molar Entropy
deltaS^{o} =ΣnS^{o} (products) ΣmS^{o} (reactants)

0th Law of Thermo
 Existence of equilibrium states
 All parts of closed equilibrium system are in a state of internal/heat equilibrium

3rd Law of Thermo
NernstPlank heat theorem  entropy of system goes to zero if temp goes to zero