Thermodynamics 1

1
Thermodynamics 1
Department of Mechanical Engineering
Dr Zamri

• Dr Mohd. Zamri Yusoff
• Department of Mechanical Engineering
• College of Engineering
• UNITEN
• Phone Ext 7255 (or 8928 7255)
• email zamri_at_uniten.edu.my

2
Chapter 1
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Basic Thermodynamics Concepts

3
Chapter Summary
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Definitions of Thermodynamics
• Basic Applications of Thermodynamics
• System, Boundary and Surrounding
• Control Volume and Control Mass
• Properties, Intensive and Extensive Properties
• Equilibrium and Quasi-Equilibrium
• State, Path, Process and Cycle
• Simple Compressible Substance
• Pressure and Temperature

4
Definitions of Thermodynamics
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Thermodynamics is the science that primarily
  deals with energy
• Energy gt Ability to cause Change
• Science that deals with heat and work and
  properties of substance that bear a relation with
  heat and work

5
1st and 2nd Laws of Thermodynamics
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• The first law of thermodynamics is simply an
  expression of the conservation of energy
  principle, and it asserts that energy is a
  thermodynamic property.
• The second law of thermodynamics asserts that
  energy has quality as well as quantity, and
  actual processes occur in the direction of
  decreasing quality of energy.

6
Statistical and Classical Thermodynamics
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Statistical Thermodynamics - Microscopic
  Viewpoint - Deal with behavior of individual
  particles by using statistical and probability
  theory
• Classical Thermodynamics - Macroscopic Viewpoint
  - As there many particles it is adequate to take
  the average effect of many molecules - Substance
  is regarded as continuum - Lead to properties
  such as Pressure, Temperature, etc.
• Most of the time Engineers use Classical
  Thermodynamics

7
Applications of Thermodynamics
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
8
Applications of Thermodynamics
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
9
Applications of Thermodynamics
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
10
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
Applications of Thermodynamics
11
Applications of Thermodynamics
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
12
Applications of Thermodynamics
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
13
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
Applications of Thermodynamics
14
Dimensions and Units
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Physical quantities can be characterized by
  Dimensions
• Magnitude assigned to dimension is called Units
• English System Still in use in U.S.A.
• SI System Universally accepted worldwide
• 7 Fundamental Dimensions in SI Systsm Length
  (m), Mass (kg), Time (s), Temperature (K),
  Electric Current (A), Amount of Light (c), Amount
  of Matter (mol)
• Dimensional Homogeneity Every term in an
  equation must have the same unit for the equation
  to be physically correct

15
Thermodynamics Systems
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Thermodynamics system is defined as a quantity of
  matter or region in space chosen for study
• The mass or region outside the system is called
  the surroundings
• System boundary is the real and imaginary surface
  that separates the system from the surrounding.
  Boundary can be fixed or movable
• May be closed or open

16
Closed System/Control Mass
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• A system of fixed mass is called a closed system,
  or control mass
• The closed system boundary does not have to be
  fixed
• No mass can cross the closed system boundary
• Energy in the form of heat and work can cross the
  closed system boundary
• If even energy is not allowed to cross we have an
  isolated system

17
Closed System/Control Mass
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
Energy, not mass, crosses closed-system boundaries
Closed system with moving boundary
18
Open System / Control Volume
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• A system that involves mass transfer across its
  boundaries is called an open system, or control
  volume
• The boundaries of a control volume is called
  control boundaries and is fixed in shape and
  position
• Energy in the form of heat and work as well as
  mass can cross the control boundaries

19
Open System / Control Volume
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
Mass and Energy Cross Control Volume Boundaries
20
Form of Energy
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• The sum of all forms of energy of a system is
  called Total Energy, which is considered to
  consist of internal, kinetic, and potential
  energies. E U mV2/2 mgz
• Internal energy represents the molecular energy
  of a system and may exist in sensible, latent,
  chemical, and nuclear forms. Represented by
  symbol, U.
• Kinetic Energy is the energy that a system
  possesses as a results of its motion relative to
  some reference frame. KE mV2/2
• Potential Energy is the energy that a system
  possesses as a results of its elevation in a
  gravitational field. PE mgz

21
Systems Internal Energy
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
Systems Internal Energy Sum of Microscopic
Energies
22
Energy Interaction
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Form of Energy not stored in a system
• Occurred at System Boundary
• In the form of Heat Transfer or Work Transfer or
  Mass Transfer
• For control mass, if the driving force for the
  interaction is temperature then the interaction
  is heat transfer otherwise it is work transfer
• For control volume can also involve mass
  transfer

23
Properties of A System
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Properties are any measurable characteristics of
  a system. eg. Pressure, temperature, volume, mass
  and density.
  
• Extensive properties are the mass-dependent
  properties of a system. i.e. the properties that
  will vary proportionally with mass of the system.
  E.g. volume
• Intensive properties are the properties that are
  not dependent on mass. Eg. Temperature, density.
  If any Extensive Property is divided by the mass
  we would also obtain an intensive property.

24
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
Intensive and Extensive Properties
25
State of a System
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Definition - A set of properties that completely
  describe the conditions or characteristics of a
  system
• At a given state, all the properties of a system
  have fixed values
• State of a system will change when the properties
  of a system change

26
Thermodynamic Equilibrium
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Thermodynamics deals with Equilibrium States
• A system is said to be in thermodynamic
  equilibrium if it maintains thermal, mechanical,
  phase, and chemical equilibrium.
• Thermal Equilibrium gt Temperature is the same
  throughout the system
• Mechanical Equilibrium gt Pressure is the same
  throughout the system
• Phase Equilibrium gt No phase change process in
  the system
• Chemical Equilibrium gt No chemical reactions

27
Process, Path and Cycle
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Process - Any change that a system undergoes from
  one equilibrium state to another is called a
  process.
• Path - The series of state through which a system
  passes during a process is called a path
• Cycle - A process with identical end states is
  called a cycle.

28
State, Path, Process and Cycle
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
Compressed Process P-V Diagram Each Point Along
the Path is in Quasi-Equilibrium State If the
Process returns to its initial State then we have
a Cycle If the Outgoing and Returning Paths are
Different Net work is Produced (ve or -ve)
29
Quasi-Equilibrium Process
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Definition - A process whereby the system remains
  infinitesimally close to an equilibrium states at
  all times
• During a quasi-static or quasi-equilibrium
  process, the system remains practically in
  equilibrium at all times
• 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 parts

30
Quasi-Equilibrium Work Producing Device
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
Quasi-Equilibrium Process is Idealized
Process Many Real Process Closely Approximate
Quasi-Equilibrium Process
Quasi-Equilibrium Process Delivers the Most Work
31
Simple Compressible System
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Definition - A system is called A Simple
  Compressible System in the absence of electrical,
  magnetic, gravitational, motion and surface
  tension effects i.e. in the absence of external
  forces
• State Postulate / Principle - The state of A
  Simple Compressible System is completely
  specified by two independent intensive
  properties. E.g. Temperature and Pressure for
  single phase system.

32
Pressure
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Pressure is defined as force per unit area
• Its unit is the pascal.
• The absolute, gage, and vacuum pressures are
  related by

33
Absolute, Vacuum and Gauge Pressure
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
34
Pressure Measurements
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Small to moderate pressure differences are
  measured by a manometer, and a differential fluid
  column of height h corresponds to a pressure
  difference of
• The atmospheric pressure is measured by a
  barometer and is determined from

35
Pressure Measuring Devices
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
Simple Manometer
Bourdon Type Pressure Measuring Devices
36
Temperature and Zeroth Law of Thermodynamics
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Temperature is a measure of hotness or
  coldness
• The zeroth law of thermodynamics states that two
  bodies are in thermal equilibrium if both have
  the same temperature reading even if they are not
  in contact.
• Basis for validity of Temperature Measurement
• More fundamental than 1st and 2nd Laws of
  Thermodynamics

37
Temperature Scale
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts

• Temperature scales used in the SI system are
  Celsius and Kelvin. The absolute Temperature
  Scale in SI is Kelvin and is related to Celsius
  by
• Temperature scale used in the English system are
  Fahrenheit and Rankine . The absolute temperature
  scale is Rankine and related to Fahrenheit by

And
And ?T(R) ?T(oF)
38
Department of Mechanical Engineering
Dr Zamri

Chap. 1 Basic Thermo. Concepts
Temperature Scale Comparison
?1 K ? 1oC ? 1.8 R ? 1.8oF