文档介绍：Source: POWER GENERATION HANDBOOK
CHAPTER 1
REVIEW OF THERMODYNAMIC
PRINCIPLES
The design, operation, and performance of electricity-generating power plants are based on
thermodynamic ,2
THE FIRST LAW OF THERMODYNAMICS
The first law of thermodynamics is the law of conservation of energy. It states that energy
can be neither created nor destroyed. The energy of a system undergoing change (process)
can vary by exchange with the surroundings. However, energy can be converted from one
form to another within that system.
A system is a specified region, not necessarily of constant volume or fixed boundaries,
where transfer and conversions of energy and mass are taking place. An open system is one
where energy and mass cross the boundaries of the system. A steady-state open system, also
called the steady-state, steady-flow (SSSF) system, is a system where mass and energy
flows across its boundaries do not vary with time, and the mass within the system remains
constant.
An SSSF system is shown in Fig. .
The first-law equation for that system is
ϩϩϩϩ⌬ϭϩϩϩϩ⌬
PE1 KE1 IE1 FE1 Q PE2 KE2 IE2 FE2 Wsf ()
ϭϭϭ
where PE potential energy [ mzg/gc, where m mass of quantity of fluid entering
and leaving the system, z ϭ elevation of station 1 or 2 above a datum,
ϭϭ
g gravitational acceleration, and gc gravitational conversion factor
ии 2 ии 2
( lbm ft/(lbf s ) or kg m/(N s )].
ϭϭ 2 ϭ
KE ic energy ( mVs /2gc), where Vs velocity of the mass.
IE ϭ internal energy (ϭ U) . The internal energy is a sole function of temperature
for perfect gases and a strong function of temperature and weak function of
pressure for nonperfect gases, vapors, and liquids. It is a measure of the
internal (molecular) activity and interaction of the fluid.
FE ϭ flow energy (ϭ PV ϭ Pmv) . The flow energy or flow work is the work
done by the flowing fluid to push a mass m into or out of the system.
⌬ϭϭϪϭϭ
heat added [