We were discussing various basic
concepts of thermodynamics such as “Thermodynamics point and path functions” in
our recent post. We have also discussed the "concept of entropy" and "Perpetual motion machines" in the field of thermal engineering.
Today we will see here the concept of
isolated system and non-isolated system used in thermodynamics with the help of
this post.
Let us first see here isolated system in thermodynamics
A system will be termed as an isolated
system in thermodynamics, if there will not be any transfer of mass or transfer
of energy i.e. heat energy or work energy across the system boundary.
In simple words we can say that, there
will not be any interaction between system and surrounding.
Therefore, for an isolated system,
change in system energy will be zero. Hence,
isolated system could be considered as fixed or constant energy system because
there will not be any transfer of energy or transfer of mass across the system
boundary and energy of system will be remaining constant.
Therefore, for an isolated system, we
will have following condition
dW
= 0 and dQ = 0
Let us recall the first law of thermodynamics and apply here for an isolated system and we will have following
equation i.e.
dE
=0
We can say from above equation, we can
say that system energy will be constant for an isolated system in
thermodynamics.
Non- isolated system in thermodynamics
There are two types of non-isolated
system in the field of thermal engineering and these are closed system and open
system.
Open system
In case of open system in
thermodynamics, mass transfer across the system boundary will take place and
energy may also transfer across the system boundary. You will see that maximum
engineering accessories or devices will follow the concept of open system.
Closed system
In case of closed system in
thermodynamics, there will not be any transfer of mass across the system
boundary. However energy may transfer across the system boundary. Therefore
close system in thermodynamics could be considered as fixed mass system also.
We will see the Carnot cycle and “What are the limitations of first law of thermodynamics” in our
upcoming posts.
Do you have suggestions? Please write in
comment box
Reference:
Engineering thermodynamics by P.K. Nag
Engineering thermodynamics by R. K. Rajput
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