What is thermal
engineering?
Thermal engineering is the science that deals with the
energy transfer to practical applications such as energy transfer power
generation, refrigeration, gas compression and its effect on the properties of
working substance.
What is
Thermodynamics?
The study of heat transfer
What is System?
A system is some
portion of the universe selected for study.
Strictly speaking a system may, or may not, contain matter or
energy. For atmospheric applications,
systems will always contain both matter and energy. The remainder of the universe is defined as
the "surroundings" of the system.
Selection of the system is primarily a matter of convenience. Systems may be classified as isolated, closed
or open.
Isolated system:
A system which cannot
exchange either matter or energy with its surroundings. The universe is defined by the First Law as
an isolated system.
Closed system:
A system which can
exchange energy, but not matter, with its surroundings.
Open system:
A system which can exchange both matter and energy with its
surroundings.
The systems in Atmospheric Thermodynamics will be “globs” of
air undergoing transformations in the atmosphere. Thus, these are really open systems, but for
the sake of simplicity, they will often be treated as closed systems.
What is State of a
system?
The state of a
system is defined by a set of system properties. A certain minimum number of such properties
are required to specify the state.
Thus in an ideal gas, any three of the four properties (pressure,
volume, number of moles, and temperature) define the state of the system. The equation of state defines the relation
among these properties.
What is an isentropic
process?
Isentropic process is also called as reversible adiabatic
process. Any reversible adiabatic process is isentropic because Entropy change
(Delta S) = integral of (Q-rev)/T. Here Q-rev is the heat transferred in an
equivalent reversible process. Since Q-rev is 0 for reversible adiabatic
process, it is isentropic.
On the other hand, every isentropic process need not
necessarily be reversible adiabatic. To find entropy change in any process, all
you need to do is to chalk out an equivalent REVERSIBLE path for the process,
and then calculate the heat change (dQ/T) for that path. If integral of that
(dQ/T) is 0, then and only then, the process is isentropic.
What is the
throttling process?
When a gas or vapour expands and flows through an aperture
of small size, the process is called as
What is Heat engine?
Device which changes internal energy into mechanical work.