Week 2 lecture 1 Flashcards
normal force exerted by a fluid per unit area
pressure
actual pressure at a given position
absolute pressure
difference between the absolute pressure and the local atmospheric pressure
gauge pressure
a region of space containing a quantity of matter whose behaviour is being investigated
system
the mass of region outside of the system
surroundings
the real or imaginary surface that separates the system from its surroundings. Prior to any thermodynamic analysis the boundary must be defined, because it is across this boundary that heat and work are to be transferred
boundary
- no mass transfer
- work & heat can cross the boundary
- called an isolated system if no energy transfer
closed system
- mass can transfer across the boundary
- work and heat can cross the boundary
- analysed as control volumes
open systems
variable parameter of a process system which has a fixed balue for a given tate of the system and is independent of the way in which that state is attained
thermodynamic function
depend on the mass of molecules in the system
extensive properties
independent of the molecular mass of the system
intensive properties
time independent description of the system
state
state of balance
equilibrium
properties which are both uniform when the system is at equilibrium
pressure and temperature
a process consists of an activity and a path
process
both the fluid and its surroundings can always be restored to their original state
reversible process
criteria of reversibility
- process must be frictionless
- difference in pressure between the fluid and its surroundings during the process must be infinitely small
- difference in temperature between the fluid and its surroundings during the process must be infinitely small
a change that the system cannot return to the initial state without there being a change in the surroundings
irreversible process
energy which is required for the phase of something to change but not change the temperature
phase change energy
fluid with some viscosity and compressibility
Real fluid
Vapourised by reduction in pressure at constant temperature
liquid
condensed by reduction in temperature at constant pressure
gas
a gas which can be condensed either by compression at constant temperature or by cooling at constant pressure
vapour
a liquid which has been cooled a few degrees below its freezing temperature
sub-cooled
a liquid which has been heated above its normal boiling point without boiling occuring
superheated
vapour in equilibrium with the fluid
saturated vapour
energy in transition other than heat
work
any form of energy transport across system boundaries not caused by a mass flow or temperature gradient
work
dW =
-P dV
energy in a system from the relative positions and interactions of its parts
internal energy
Enthalpy equation
H = U + PV
First law of thermodynamics
Energy cannot be created or destroyed
process with constant temperature
isothermal
process with constant pressure
isobaric
process with constant volume
isochoric/isometric
Isothermal system
What Q =
Q = W
ISOTHERMAL SYSTEM
Isochoric system
What Q=
mCvdT
Isobaric system
What Q=
mCpdT
Isobaric system
What W=
W= P dV
Process where no heat is transferred betwen system and surroundings
adiabatic process
Adiabatic process
R =
Cp - Cv
Adiabatic process
γ =
Cp/Cv
Any thermodynamic process that can be expressed by the reversible law pVn = constant
Polytropic Process
https://www.thermal-engineering.org/what-is-polytropic-process-definition/
