Thermodynamics has four laws: 0th, 1st, 2nd, and 3rd. Thermodynamics is the study of
how energy changes from one form to another. Energy exists in several forms:
potential, kinetic, chemical, thermal, electrical, nuclear and much much more! We
all love lord Kelvin, he cam up with plenty of equations and is a unit of measure for
temperature. We learned that the European and metric system is so much better
than the English system of measure. There are open and closed systems. Open
systems allow mass to enter and leave where as closed systems do not. Out bodies
are open systems. Properties are characteristics of a system. There are intensive,
extensive, and specific properties. Equilibrium is our friend. It is easy to study things
in equilibrium because ther
no ange.
0th Law of
Thermodynamics: If two sys
s a in th
al equilibrium with a third system,
they are also in thermal equilibriu
ith
h ot
. Six important steps to solve
thermodynamics problems go as follows, given, find, system identification,
assumptions, basic equations, solution. Mechanical work is the energy transfer
associated with force acting through a distance.
∫
Kinetic energy is the minimum mechanical work required to accelerate an object of
fixed mass from rest to a given velocity.
Potential energy is the
minimum mechanical work required to rais an object of fixed mass a given elevation
within the gravitational field.
Microscopic energy comes in
translational, rotational, and vibrational.
Having no heat transfer
creates an adiabatic process. Conservation of energy states that energy can neither
be created nor destroyed.
There are phases of matter.
Sub-cooled liquid, saturated liquid, saturated liquid-vapor mixture, saturated
vapor, and superheated vapor. The critical point is a when all the phases are present
at one time. Total enthalpy:
The property tables help you determine a
lot of things about the state of a liquid/vapor. Ideal gas is an “imaginary” substance
that has certain characteristics, negligible molecular volume, inter-molecular forces.
R is the universal constant.
Conservation of mass is a
conserved property and it cannot be created or destroyed during a process.
̇ Mass and energy balances for
The mass flow rate goes as follows ̇
a steady flow process
Steady flow devices are nozzles, diffusers,
turbines, and compressors. A throttling valve is a steady flow engineering device
used to produce a significant pressure drop along with a large drop in temperature.
A heat exchanger is a steady flow engineering device used to carry out heat between
two fluid streams without or with direct mixing called mixing chamber. Second law
of thermodynamics establishes direction and possibility for process, provides means
for measuring the quality of energy, and determines theoretical limits regarding the
performance of engineering devices. There are reversible and irreversible processes.