Thermodynamics II
Lecture 1
Review
Outline
• Instructors; Dr. Saleh Abo-Elfadl
•
Dr. Othman Hassan
([email protected])
• Mid-terms; Midterm1 ….. End of October (tentative) 25/50
•
Midterm2 ….. End of November (tentative) 25/50
• Bonus… 5/50 attendance of tutorials
• Final ……. 100
•
Definition of Thermodynamics
Thermodynamics is the science
of :
Energy and Power
Dimensions and Units
• Any Physical Quantity can be characterized by a Dimension
• The magnitudes assigned to the dimensions are called units
Dimensions and Units
• Primary or Fundamental Dimensions (Mass, Length, Time,
Temperature)
• Derived or Secondary Dimensions (Velocity, Energy, Volume…)
Closed and Open Systems
• Difference between closed system (control mass) and open
system (control volume)
• Closed System
Open System
Properties of a System
• Any Characteristic of a system is called a property (Pressure,
Temperature, Volume, Mass)
• Intensive properties are independent on the mass or size of
the system (Pressure, temperature, …)
• Extensive properties (Specific Properties) are dependent on
the mass or size of the system (Mass, Volume, …)
State and Equilibrium
• State, a condition at which all properties of a system can be
measured
• At Equilibrium states there is no unbalanced potentials
• Thermal Equilibrium (Temperature)
• Mechanical Equilibrium (Pressure)
• Phase Equilibrium (Phase)
• Chemical Equilibrium (Chemical)
• To Fully define the state of a system at least two independent
properties must be defined
Process and Cycle
• Any change in the system state from an equilibrium state to
another is a process
• The series of states through which the system passes during a
process is named a path
Process and Cycle
• Isothermal process (Constant temperature)
• Isobaric (Constant Pressure)
• Isochoric (Constant Volume)
• The system is said to undergone a cycle when it returns to its
initial state at the end of the process
The Zeroth law of Thermodynamics
If two bodies are in thermal equilibrium with a third body, they
are also in thermal equilibrium with each other.
In other words (if body A is in thermal equilibrium with body B
and Body B is in thermal equilibrium with Body C then; Body A is
in thermal equilibrium with Body C)
This law serves as a basis for the validity of temperature
measurements
SI Temperature Scale
• Relation between Celsius and Kelvin (absolute) temperatures
• T (Kelvin) = T (Celsius + 273.15)
Pressure
• Pressure is a normal force exerted by a fluid per unit area
• Its units is Pascal (Pa)
•
•
1Pa = 1 N/m2
Absolute and Gauge Pressures
•
Variation of Pressure with Depth
Forms Of Energy
• Kinetic Energy (KE)
• Potential Energy (PE)
• Internal Energy (U)
• Together they form the total Energy (E)
Heat
• Heat is the form of energy that is transferred between two
systems
• Conduction, Convection, and Radiation are the heat transfer
mechanisms
• Conduction occurs inside solids and fluids
• Convection occurs between a solid and a fluid
• Radiation occurs between solid bodies regardless if there is a
medium between them or not
Work
• Work is the energy transfer associated with a force acting
through a distance
• The rate of work per unit time is named power
• There is mechanical, electrical and magnetic works
First Law of Thermodynamics
• It is known also as the energy conservation principle
• It states that “Energy can be neither created nor destroyed
during a process; it can only change forms”
Energy Balance of a System
• Total Energy coming in to the system – Total energy leaving
the system = Change in total energy of the system
•
Mechanisms of Energy Transfer
• Heat Transfer Q
• Work Transfer W
• Mass Flow m
Example
Solution
•
Properties of Pure Substance
• Pure substance is a substance that has a fixed chemical
composition throughout.
• A mixture of two or more phases of a pure substance is still a
pure substance as long as the chemical composition of all
phases is the same.
• Ex. A mixture of ice and liquid water
Phase Change Process of Pure Substance
• Compressed
Liquid
Saturated
liquid
Saturated Liquid-Vapor Mix.
Phase Change Process of Pure Substance
•
Saturated
Vapor
Superheated
Vapor
Phase Change Process of Pure Substance
Property Diagrams;1- T-v diagram
2- P-v Diagram
3- P-T Diagram
Property Tables
Enthalpy
• Enthalpy is the combination of both the internal energy and
the flow energy
Saturated Liquid-Vapor Mix.
• Quality (x) is defied as;
Properties of Mixture State
•