chap 2 part 1 Flashcards
Wec, Expansion Contraction Work
work done due to the movement of system boundaries relative to one another, SIZE OF THE SYSTEM MUST CHANGE
When is work positive?
when work is done ON the system (Wec is negative because volume decreases and work is being done BY the system)
Ws, Shaft Work
work being added or removed WITHOUT a change in volume of the system, (turbine, pump, mixing)
Wflow, Flow work
work done when mass crosses system boundaries
Friction
decreases work available from a process
lost work
disorder generated, potentially useful work becomes useless thermal energy.
can be minimized but not eliminated
reversible process
approximation of a real process to which a correction factor is applied to estimate the results of an actual process - a reversible process has no dissipative losses and may return to its prior state by reversing its motion.
Velocity Gradient
dissipation of directional motion (kinetic energy) into random motion (internal energy) due to viscosity
Pressure gradient
lead to velocity gradients in a viscous fluid
Reversible
a process without dissipative losses
Is heat a property of the system?
NO it is a form of interaction at the boundary that transfers internal energy
diathermal wall
idealized system boundary that has no resistance to heat transfer but is impervious to mass
isothermal
constant temperature
isobaric
condition of constant pressure
isochoric
condition of constant volume
adiabatic
path without heat transfer
State property
a path independent property
closed system
no mass flow in or out of system (HEAT AND WORK ARE ONLY 2 WAYS a closed system can interact with surroudings) -> THINK U, INTERNAL ENERGY
Is Q positive or negative when the system gains heat?
POSITIVE
when writing balances what do the left and right sides of the balance represent?
left side: changes INSIDE system
right side: changes due to interactions AT system boundaries
Heat Capacity
how a substance responds to a certain amount of heat being added/taken away
throttles
device used to reduce pressure of a flowing fluid without extracting any shaft work with negligible fluid acceleration
CHANGE IN ENTHALPY = 0 ( ISENTHALPIC)
nozzles
convert pressure drop into kinetic energy
CHANGE IN ENTHALPY = 1/2 (CHANGE IN VELOCITY) ^2
