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Thermodynamics II

Thermodynamics II . Lecture 1 Review. Outline. Instructors; Dr. Saleh Abo- Elfadl Dr. Othman Hassan (othman.hassan@eng.au.edu.eg) Mid-terms; Midterm1 ….. End of October (tentative) 25/50

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Thermodynamics II

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  1. Thermodynamics II Lecture 1 Review

  2. Outline • Instructors; Dr. Saleh Abo-Elfadl • Dr. Othman Hassan (othman.hassan@eng.au.edu.eg) • Mid-terms; Midterm1 ….. End of October (tentative) 25/50 • Midterm2 ….. End of November (tentative)25/50 • Bonus… 5/50 attendance of tutorials • Final ……. 100

  3. Definition of Thermodynamics Thermodynamics is the science of : Energy and Power

  4. Dimensions and Units • Any Physical Quantity can be characterized by a Dimension • The magnitudes assigned to the dimensions are called units

  5. Dimensions and Units • Primary or Fundamental Dimensions (Mass, Length, Time, Temperature) • Derived or Secondary Dimensions (Velocity, Energy, Volume…)

  6. Closed and Open Systems • Difference between closed system (control mass) and open system (control volume) • Closed System Open System

  7. 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, …)

  8. 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

  9. 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

  10. 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

  11. 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

  12. SI Temperature Scale • Relation between Celsius and Kelvin (absolute) temperatures • T (Kelvin) = T (Celsius + 273.15)

  13. Pressure • Pressure is a normal force exerted by a fluid per unit area • Its units is Pascal (Pa) • 1Pa = 1 N/m2

  14. Absolute and Gauge Pressures

  15. Variation of Pressure with Depth

  16. Forms Of Energy • Kinetic Energy (KE) • Potential Energy (PE) • Internal Energy (U) • Together they form the total Energy (E)

  17. 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

  18. 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

  19. 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”

  20. Energy Balance of a System • Total Energy coming in to the system – Total energy leaving the system = Change in total energy of the system

  21. Mechanisms of Energy Transfer • Heat Transfer Q • Work Transfer W • Mass Flow m

  22. Example

  23. Solution

  24. 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

  25. Phase Change Process of Pure Substance • Compressed Saturated Saturated Liquid-Vapor Mix. Liquid liquid

  26. Phase Change Process of Pure Substance • Saturated Superheated Vapor Vapor

  27. Phase Change Process of Pure Substance

  28. Property Diagrams;1- T-v diagram

  29. 2- P-v Diagram

  30. 3- P-T Diagram

  31. Property Tables

  32. Enthalpy • Enthalpy is the combination of both the internal energy and the flow energy

  33. Saturated Liquid-Vapor Mix. • Quality (x) is defied as;

  34. Properties of Mixture State

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