Lecture 5 Flashcards
SFEE
steady flow energy equation
enthalpy
internal energy + work done
why are we able to simplify the SFEE to
Q - W = m (h2 -h1) (all with respect to time
as enthalpy is often by 1000 times the largest terms so can ignore kinectic and potential terms especially for gases
simplify the SFEE to bernoullis equation
internal energy does not change and heat is not added
use density rather than specific volume (v = 1/density)
treat density as constant
no work input
for closed systemm
Q -W =m(u2 -u1)
for steady flow thermal systems
SFEE with enthalpy terms
for steady flow fluid systems with work
SFEE densities and internal energy removed
steady flow fluid systems
bernoullis equation
what does a turbine do
extracts KE from flow and turns it into motion
draw a diagram of a turbine
take in high temperature and pressure fluid
out goes low temperature and pressure fluid
compressor takes
low temperature low pressure fluid and compresses it doing work on the fluid
in a powerstation what is the name of compresses that pressurise the water
feed pumps
work is needed to drive a compressor or tubine
work is needed to drive a compressor work is extracted from a turbine
SFEE simplification for turbines and compressors
adiabatic Q = 0
gases and steam kinetic and potential energy terms are negligible
SFEE eqation for turbine and compressor
-W = mass flow rate (h2 - h1)
or workrate = mass flow rate (h1-h2)
SFEE wind and water turbines
kinetic energy term and enthalpy term