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CH-107

Lecture

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CHEMICAL
ENGINEERING
THERMODYNAMICS-I

Dr
...
M Smith, 7th Edition
...

• “Thermodynamics, an Engineering
Approch” by Yunus A Cengel
...


CHEMICAL ENGINEERING THERMODYNAMICS-I

2

Faculty of Chemical Engineering, NEDUET

Lecture Outlines
Fundamentals of Thermodynamics
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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Fundamentals

What is Thermodynamics?
 The science of energy, that
concerned with the ways in
which energy is stored within a
body
...

Thermodynamics applies to a wide variety of
topics in science and engineering,
especially physical chemistry, chemical
engineering and mechanical engineering, but also
in fields as complex as meteorology
...

 Energy transformations – mostly
involve heat and work movements
...


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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Fundamentals

Brief History
• 1st and 2nd law of thermodynamics emerged simultaneously in the
1850s
...

• It started at the time of industrial revolution at the beginning of
generating power by burning fossil fuels
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• Historically, thermodynamics developed out of a desire to increase
the efficiency of early steam engines
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 Only a few variables are used to describe the state of matter
such as temperature, pressure and volume
...

 Studies the average behavior of large groups of Molecules

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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Fundamentals

Types Of Thermodynamics
 Statistical thermodynamics formulate the microscopic state
 Defines the properties of a system based on the behavior of
molecules/atoms
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 A large no of variables are needed to describe the state of
matter
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 Power Production
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 In an equilibrium state there are no unbalanced potentials, or driving
forces, between macroscopically distinct parts of the system
...


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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Fundamentals

State Of Equilibrium
We only Apply Thermodynamics at equilibrium
 Mechanical Equilibrium
Mechanical
 no unbalanced forces
Equilibrium
 Chemical Equilibrium
 no chemical potential differences
 Thermal Equilibrium
 no temperature differences
 Phase Equilibrium
 No phase change

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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Fundamentals

Principles of Thermodynamics?
• It consist of four laws
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• Each law will give us a concept and define a property
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• This law is also called a common sense law
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“The zeroth law was not initially recognized as a separate law of
thermodynamics, as its basis in thermodynamical equilibrium was
implied in the other laws
...
As it was impractical to
renumber the other laws, it was named the zeroth law
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• This law is also called a quantitative law
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• Concept of Perpetual motion is the motion of bodies that continues
forever
...

CHEMICAL ENGINEERING THERMODYNAMICS-I

14

Faculty of Chemical Engineering, NEDUET

Fundamentals

Principles of Thermodynamics?
• Thus, machines that extract energy from finite sources will not
operate indefinitely, because they are driven by the energy stored in
the source, which will eventually be exhausted
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• A perpetual motion machine of the second kind is a machine which
spontaneously converts thermal energy into mechanical work
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• A perpetual motion machine of the third kind is usually defined as
one that completely eliminates friction and other dissipative forces,
to maintain motion forever
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• This law is also called a qualitative law
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• It give us one hope, If you want to converts energy completely in to
work and to get 100% efficiency than you need to go down to O
Kelvin other wise you gone waste some of that energy
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• The third law of thermodyanmcis provides a datum for the
measurement of entropy and introduce the concept of absolute zero
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• Third law say in simple words that “It is impossible to achieve zero
Kelvin”
...
16 degree C
...


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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Basic Concept

System, surroundings and boundary
 System: A quantity of matter or a
region in space chosen for study
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 It may change in shape and size
 Some time a system is also referred as
control volume cv
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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Basic Concept

System, surroundings and boundary
 Surroundings: The mass or region
outside the system
...

 The combination of matter and space
external to the system
...

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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Basic Concept

Type of system
(Open system)



Open system – both mass and
energy can cross the selected
boundary






Examples
an open cup of coffee
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Pump, turbine, compressor etc
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Pressure cooker
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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Basic Concept

Type of system
(isolated system)



Isolated system – neither
mass nor energy can cross
the selected boundary

 Example
 coffee in a closed, well-insulated
thermos bottle
...


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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Basic Concept

Properties of a system
 A property is any characteristic (which can be quantitatively
evaluated) that can be used to describe the state of a system e
...


Essential features of a property
...

 The value of the property should not depend upon the past history of
the system
...


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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Basic Concept

Properties of a system
Properties of a system is a measurable characteristic of a system that is
in equilibrium
...

 Intensive – Are independent of the amount of mass: e
...
g: mass, volume, total
energy, enthalpy
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 The property of the one mole of a material is referred as specific property
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 a set of properties that describes the conditions of a system
...
Mass m, Temperature T, volume V

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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Basic Concept

State, Equilibrium and Process
 Steady State – it is the property of a system at any specified
location are independent of time, than the system is said to
be in a steady state
...


Process

Property held
constant

isobaric

pressure

isothermal

temperature

isochoric

volume

isentropic

entropy
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CHEMICAL ENGINEERING THERMODYNAMICS-I

Faculty of Chemical Engineering, NEDUET

Basic Concept

State, Equilibrium and Process
Quasi Equilibrium Process – A quasiequilibrium process can be viewed
as a sufficiently slow process that allows
the system to adjust itself internally
so that properties in one part of the system
do not change any faster than
those at other
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Isobaric process: A process during which the pressure P remains
constant
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...
For such a process ∆Q= 0

CHEMICAL ENGINEERING THERMODYNAMICS-I

32

Faculty of Chemical Engineering, NEDUET

Basic Concept

Types of Thermodynamics Processes
 Cyclic process - when a system in a given initial
state goes through various processes and finally
return to its initial state, the system has undergone
a cyclic process or cycle
...
In
doing so, it leaves no change in the system or
boundary

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