chapter 3 and 4 Flashcards
Phase
Matter which is homogeneous throughout in both its chemical and physical structure. ex- air = single phase
water with ice = 2 phase
Homogeneous
Matter is all the same state, solid, liquid, or gas
Pure Substance
A substance that is uniform and invariable in chemical composition. ex- helium, water and ice
liquid to gas
Vaporization
gas to liquid
Condensation
solid to liquid
Melting (fusion)
liquid to solid
freezing
solid to gas
sublimation
gas to solid
deposition
Phase Rule
f=c-p+2 f= degrees of freedom c=number of components p=number of phases at equilibrium for a system of any composition.
The ______ state of a closed system at equilibrium is its condition as described by the values of its intensive thermodynamic properties.
intensive
For a simple compressible system, specifying any _____ independent intensive thermodynamic properties will fix the other intensive thermodynamics properties of the system.
2
Examples of intensive properties
(Doesn’t depend on amount of matter or size)
Pressure, Temperature, Density, Specific Volume, Internal Energy, Enthalpy, Entropy.
saturation temperature
temp at which a phase change happens for a specific pressure
True or false. Within two-phase regions, pressure and temperature ARE independent.
False
Critical point
the point where saturated liquid and saturated vapor lines meet
isotherms
line of constant temperature
High left to low right on p-v
isobar
line of constant pressure
low left to high right t-v
true of false. while in dome if p-v or t-v diagram temp and pressure remain constant from specific volume changes
true
compressed liquid
a liquid with a temp lower than saturation temp for
quality (x) equation
percent of mixture that is vapor
x=mvapor/(mliquid+mvapor)
superheated vapor
when temp is higher than the sat temp for corresponding pressure
total volume saturated liquid formula
V=vf+x(vg-vf)
vf=liquid vg=vapor
specific enthalpy (h)
h=u+pv
enthalpy= internal energy + work due to expansion
linear interpolation
vactual= v@ref1 +[(v@ref2 - v@ref1)/(ref2-ref1)] (actual-ref1)
Extensive form of internal energy and enthalpy
U and H (uppercase is important)
Intensive form of internal energy and enthalpy
u and h (lowercase is important)
Constant volume process equation
u2-u1=cv(T2-T1)
Constant pressure process equation
h2-h1=cp(T2-T1)
specific heat ratio
k=cp/cv
True of False. For a liquid, there is little change in v,u,h,and s at different Temperatures and fixed Pressure.
False
there is little change at different Pressures and fixed temperature.
incompressible substance
any substance whose properties do not change with pressure, or have very minor changes.
generalized compressibility only applies to _____
gases
what does a horizontal line above a variable mean
molar unit.
unit times molar weight (g/mol)
what does it mean when z=1
ideal gas
P is much less than Pc
T is much greater than Tc
pressure and temp reduced equations
Pr=P/Pc Pc=critical pressure
Tr=T/Tc Tc=critical temp
ideal gas equation (3 forms)
pv=RT (lowercase v is important)
pV=mRT m=mass
pV=nRT (with line above R) n=number of moles
if a gas behaves as an ideal gas, then its specific internal energy and specific enthalpy, depends only on _____
temperature
polytropic process formula and process for N=1,0,and k
pv^N=constant or pV^N=constant
N=1 - isothermal pv=Constant
N=0 isobaric process p=Constant
N=k adiabatic process Q=0
Mass rate balance
the rate at which mass accumulates in the control volume is the difference between mass flow in and flow out
Energy rate balance
the rate at which energy accumulates. the difference between heat flow rate in and power out AND difference between mass carries energy into and out of control volume
1st law of thermodynamics for open system
rate of energy accumulation= Qdot - Wdot +mdot-i (ei) - mdot-e (ee)
Flow work
work done BY the flow (Wdot)
control volume work
work done BY the control volume (Wdot-cv) integral of pdv
ex - work done by turning a shaft or electricity
work done ON system by mass entering
negative
work done On environment as mass exits
positive
steady state Qdot=0 if
IMPORTANT
small surface area
system is insulated
small time interacting with system and environment
steady state Wdot=0 if
IMPORTANT
no change in system volume (fixed container)
no turbines/pumps or electrical devices
steady state gz=0 if
IMPORTANT
no significant change in elevation from inlet and outlet
vi^2-ve^2=0 if
IMPORTANT
inlet and outlet are the same size
Nozzle
passage where velocity increases in direction of flow
Ve greater than Vi
Pe less than Pi
Enters wide end exits narrow end
diffuser
passage where velocity decreases in direction of flow
Ve less than Vi
Pe greater than Pi
enters narrow end, exits wide end
Turbine
a device in which –power is developed– as a result of a gas or liquid passing through a set of blades attached to a shaft free to rotate.
compressors and pumps
devices in which –work is done on the substance– flowing through them to change the state of the substance, typically to –increase the pressure and/or elevation–
difference between compressor and pump
compressor- uses gas
pump - uses liquid
Heat exchanger
Direct contact
a mixing chamber in which hot and cold streams are –mixed directly–
ex- water faucet
heat exchanger
tube-within-a-tube counterflow
a gas or liquid steam is –separated– from another gas or liquid by a wall through which energy is conducted. heat transfer occurs from the hot stream to the cold stream as the streams flow in opposite directions.
ex- radiator
specific heat (c) definition
The heat required to raise the temperature of a unit mass of a substance by a certain amount. (usually 1 degree)
