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1.Basic Concepts and Terminologies

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**1. **1.Basic Concepts and Terminologies

**2. **Basic Concepts and Terminologies
1.1 Introduction
1.2 Conservation Principle
1.3 Property, State and Phase
1.4 Process and Cycle
1.5 The 0th Law of Thermodynamics
1.6 Units and Dimensions

**3. **Basic Concepts and Terminologies 1.1 Introduction
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**4. **Basic Concepts and Terminologies
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**5. **Basic Concepts and Terminologies
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**6. **Basic Concepts and Terminologies
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**7. **Basic Concepts and Terminologies 1.2 Conservation Principle Any thermal-fluid phenomena can be described by a closed set of the conservation equations of mass, momentum and energy with relevant property and constitutive relationships.
Integral and Differential Approaches
There are two different approaches to mathematically describe any thermal-fluid phenomena involving mass, momentum and energy transfer.

**8. **Basic Concepts and Terminologies Integral Method
A system is defined in terms of definite mass or definite volume in space.
-control mass (closed system)
-control volume (open system)
Differential Method
The conservation principle is applied to an infinitesimal volume resulting in partial differential equations.

**9. **Basic Concepts and Terminologies -Control mass (closed system)
Surroundings
isolated system - no interaction with the surrounding
-Control volume (open system)
Surroundings

**10. **Basic Concepts and Terminologies Conservation Principle
for any conserved quantity, ?, per unit mass
The diffusive flux, J, is given as

**11. **Basic Concepts and Terminologies Mass Conservation for a Control Volume

**12. **Basic Concepts and Terminologies Mass Conservation in a Differential Form

**13. **Basic Concepts and Terminologies Momentum Conservation for a Control Volume

**14. **Basic Concepts and Terminologies Momentum Conservation in a Differential Form

**15. **Basic Concepts and Terminologies Energy Conservation for a Control Volume

**16. **Basic Concepts and Terminologies Energy Conservation in a Differential Form
Total energy balance
Thermal energy balance

**17. **Basic Concepts and Terminologies In either integral and differential descriptions there can be many different combinations of the conservation equations and complementary constitutive relationships.
The proper choice depends on the problem under consideration and the information required as a solution.
The essence of this course is to understand these basic approaches and how to apply them to real engineering problems involving various thermal-fluid phenomena.

**18. **Basic Concepts and Terminologies How is Energy stored in Gas?
Intermolecular potential energy; negligible at low
Molecular kinetic energy; translation
Intramolecular energy; rotation, vibration, electronic
Degree of freedom: f (Equipartition Principle)
f=3 for monatomic gas, such as He
f=6 for diatomic gas, such as O2
(3 for translation, 2 for rotation, 1 for vibration)
f=9 for H2O
(3 for translation, 3 for rotation, 3 for vibration)

**19. **Basic Concepts and Terminologies Example 1 (WSB p131)
Control volume: Turbine
Inlet state: Fixed
Exit state: Fixed
Process: SSSF
Model: Steam tables

**20. **Basic Concepts and Terminologies In classical thermodynamics we do not care about
how energy is stored in a system. It may be of interest
to understand thermodynamic properties, e.g. the
amount of energy required to raise the temperature by
a given amount.
However it helps conceptually to understand the
relationship between the classical or macroscopic
views and the statistical or microscopic views.

**21. **Basic Concepts and Terminologies 1.3 Property, State, Phase
We need to know various thermodynamic properties
for any quantitative description of matter.
Property: Any quantity of the system, which is independent of the path or history how the state is reached.
State: The state is defined in terms of a certain observable macroscopic properties such as temperature, volume, pressure, etc. Each property in a given state of the system should have only one definite value.
Phase: A homogeneous quantity of matter of the same type of molecules, e.g. solid or gas phase.

**22. **Basic Concepts and Terminologies

**23. **Basic Concepts and Terminologies Relationship between State and Properties

**24. **Basic Concepts and Terminologies Extensive and Intensive Properties Extensive Property : proportional to mass
Intensive Property : independent of mass

**25. **Basic Concepts and Terminologies (Thermodynamic) Properties
Specific volume : volume per unit mass
Density : inverse of the specific volume
Pressure : the normal component of force per unit area. The pressure is the same in all directions in a fluid in equilibrium.
Temperature : measure of hotness or coldness.
Exact definition depends on the 0th law of thermodynamics and the temperature scale.
etc.

**26. **Basic Concepts and Terminologies Transport Properties
Diffusive transport by chaotic molecular motions
Mass: diffusion coefficient(D)
Momentum: viscosity(?)
Energy: thermal conductivity(?)
Dimensionless numbers:
Prandtl number= ?/?
Schmidt number= ?/D
Lewis number= ?/D

**27. **Basic Concepts and Terminologies 1.4 Process and Cycle
Process: A path of states through which the system
passes
Cycle: A process the initial and final states are identical
Property Final
B state
Initial Cycle
state
Property A

**28. **Basic Concepts and Terminologies Equilibrium: A state of balance, which goes through no change with time when it is isolated from the surrounding.
-Mechanical Equilibrium
-Thermal Equilibrium
-Phase Equilibrium
-Chemical Equilibrium
Nonequilibrium
Equilibrium

**29. **Basic Concepts and Terminologies Quasi-equilibrium process: A process in which the deviation from equilibrium is infinitesimal. All the states the system passes through may be considered as equilibrium states.
Property FS
B
FS
IS
IS
Property A

**30. **Basic Concepts and Terminologies Processes
Isothermal: temperature fixed
Isobaric: volume fixed
Isochoric: pressure fixed
Isentropic: entropy fixed
Isenthalpic: enthalpy fixed

**31. **Basic Concepts and Terminologies 1.5 The 0th Law of Thermodynamics
Temperature
When two systems are in thermal equilibrium with a third system, they also are in thermal equilibrium with each other.
This is the basis of any temperature measurement using a reference system, called a thermometer.

**32. **Basic Concepts and Terminologies Temperature Scale
Ice point: the temperature of a mixture of ice and water in
equilibrium with saturated air at 1atm
Steam point: the temperature of a mixture of steam and
water in equilibrium with saturated air at 1atm
Celsius(°C): ice point=0°C
steam point=100°C
Fahrenheit(F): ice point=32F
steam point=212F
At the 10th GPM(1954) the Celsius scale was redefined in
terms of the triple point of water(0.01°C) and the ideal
gas temperature scale.

**33. **Basic Concepts and Terminologies Absolute Temperature Scale
K(Kelvin) = °C + 273.15
R(Rankine) = F + 459.67
ITS-90: International Temperature Scale(1989)
Fixed and easily reproducible points that are
assigned definite numerical values of temperature
Specified formulas relating temperature to the
readings on certain temperature-measuring
instruments for interpolation between the defining
fixed points

**34. **Basic Concepts and Terminologies

**35. **Basic Concepts and Terminologies 1.6 Units and Dimensions
SI unit: second, meter, kilogram are the basic
units for time(t), length(L) and mass(M).
F=ma
Force: ML/t2 – Newton(N)
Energy: ML2/t2 – Joule(J)
Pressure: M/Lt2 – Pascal(Pa)
English Engineering System: sec, ft, lbm, lbf
Do you understand the difference?
Force, Weight, Mass ?
Energy, Power ?
Momentum, Pressure, Force ?

**36. **Basic Concepts and Terminologies Conversion of Units
1 lbm = 0.45359237 kg
1 ft = 0.3048 cm
1 ft = 12 in
or

**37. **Basic Concepts and Terminologies Specific Volume

**38. **Basic Concepts and Terminologies Pressure
1 Pa = 1 N/m2
1 bar = 0.1 MPa = 105 Pa
1 atm = 101325 Pa = 14.696 lbf/in2 (psi)
Absolute pressure and gauge pressure
gauge pressure
absolute pressure