Lecture 2 / ENERGY Flashcards
can exist as thermal, mechanical, kinetic, potential, electric, magnetic, chemical and nuclear. Their sum constitutes the total energy E of the system. e = u + ke + pe = u + V²/2 + gz (kJ/kg)
total energy
a system possesses as a whole with respect to some outside reference frame, such as kinetic and potential energies.
macroscopic forms of energy
related to the molecular structure of a system and the degree of the molecular activity, independent of the outside reference frames.
microscopic forms of energy
The sum of all the microscopic forms of energy, denoted by U.
internal energy
is the energy that a system possesses as a result of its motion relative to some reference frame. When all parts of a system move at the same velocity,
kinetic energy
is the energy that a system possesses as a result of its elevation in a gravitational field.
potential energy
____________ whose velocity and elevation of the **centre of gravity remain constant **during a process are often referred to as _____________
closed systems , Stationary systems
The amount of mass flowing through a cross section per unit time. ṁ = ρV̇
mass flow rate ṁ
The flow of thermal energy from higher temperature to lower temperature via conduction, convection and radiation.
heat transfer
is equal to force multiplied by displacement.
work
highest quality of energy, for example, can always be converted to an equal amount of thermal energy ( also called heat )
ELECTRICITY
can exist in numerous forms such as thermal, mechanical, kinetic, potential, electric, magnetic, chemical, and nuclear, and their sum constitutes the total energy E of a system
ENERGY
typically involve fluid flow for long periods of time, and it is convenient to express the energy flow associated with a fluid stream in the rate form
CONTROL VOLUMES
the form of energy that can be converted to mechanical work completely and directly by an ideal mechanical device such as an ideal turbine
MECHANICAL ENERGY
energies are the familiar forms of mechanical energy.
KINETIC AND POTENTIAL
Is defined as the form of energy that is transferred between two systems ( or a system and its surroundings ) by virtue of temperature difference.
Heat
A process during which there is** no heat transfer** is called an ____________
Adiabatic process
Is a energy interaction between a system and its surroundings
Work
conservation of the quality of energy, not the quantity
Energy Conservation
The magnetic, electric, and surface tension effects are significant in some specialized cases only and are usually ignored
total energy of a system
Motion of a particle system
Sensible energy
Phase change
Latent
__________can cross the boundary of a
closed system in two distinct forms:_____________
Energy ; heat and work
is energy in transition. It is
recognized only as it crosses the
boundary of a system
heat
have inexact differentials designated
by the symbol δ. differential amount of heat or work
is represented by δQ or δW, respectively, instead
of dQ or dW
Path functions
The net change (increase or decrease) in the total energy of the system during a process is equal to the difference between the total energy entering and the total energy leaving the system during that process
ENERGY BALANCE
An energy interaction that is
not caused by a temperature difference between
a system and its surroundings is work
Work Transfer, W
the system serves as an additional mechanism of
energy transfer. When mass enters a system,
the energy of the system increases because
mass carries energy with it
Mass flow
Thermodynamics provides no
information about the absolute
value of the total energy. It deals
only with the __________________, which is what matters in
engineering problems
change of the total
energy
