met 211 introduction-to_thermdynamics_1-4_
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Chapter 2
Part 1 of 4
Thermodynamics is the Science of
energy transfer and effect of this
transfer on the substance properties.
Dr.Khaled S. Al-zahrani
Dr.Khaled S. Al-zahrani
Examples:
Heat energy Mechanical energy
Petrol Engine
Mechanical energy Electrical energy
Generator
Electrical energy Mechanical energy
Electric motor
Chemical energy Electrical energy
Full cell
Electrical energy Cooling effect
Refrigerator
Heat energy Electrical energy
Electrical power generator
The working Substance
The working substance: Absorbs heat or rejects heat.
Does work or work is done on it.
Compressed or expanded
Heated or cooled
So that the desired energy transfer is achieved.
Examples:
O Steam in steam turbine
O Fuel in car engine
O Air in air compressor
Dr.Khaled S. Al-zahrani
Dr.Khaled S. Al-zahrani
Pure Substance: Homogeneous composition
Constant chemical structure over phase change
Examples:
Water
Gold
Copper
Pure Substance
Constant chemical structure
over phase change
Examples:
Water
Gold
Copper
Mixture
Combination of two or more
substances
Examples:
Brass
Coffee
Soil
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System:
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Type of Systems: Closed
Open
Isolated
Adiabatic
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Closed System:
Non-Flow system, only ENERGY flow across the boundary.
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Open System:
Flow system, only ENERGY & MASS flow across the boundary.
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Isolated System:
Non-Flow or heat system, NO ENERGY or MASS flow across
the boundary.
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Adiabatic System:
No HEAT transfer across the system boundaries.
Dr.Khaled S. Al-zahrani
Thermodynamic Properties
Properties is a measurable characteristics of a system
Examples:
Pressure
Volume
Temperature
Density
Enthalpy
Entropy
Specific heat
Any Thermodynamic System can be described with help of its properties
Dr.Khaled S. Al-zahrani
System State
• The thermodynamic system is described in terms of certain values of
some properties.
• Any Two independent properties can completely fix the state of the
system
Thermodynamic Process
• A process is defined as the succession of specified changes in
the state of the system
• If the value of one of the properties is kept constant the process
is known by the properties which is kept constant.
Dr.Khaled S. Al-zahrani
Examples of thermodynamics process
Isobaric process P = C
Isochoric process V = C
Isothermal process T = PV = C
Isentropic process S = C
P
V
P = C
V =
C
T = PV = C
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Cyclic Process
If a system undergoes various processes in succession in
such way that at the end of the last process it returns to its
original state.
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0th 1st 2ed 3ed
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0th Zeroth Law
A B B C
A C
Thermal Equilibrium
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Joules experiment
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Conservation of energy
E Initial + E entering = E final + E leave
Forms of Energy:
1. Gravitational Energy PE= g×Z = 9.81×Z
2. Kinetic Energy KE = 𝑪𝟐
𝟐
3. Displacement Energy DE = Pv
4. Internal Energy U
5. Heat Energy H
6. Work Energy W
Dr.Khaled S. Al-zahrani
Displacement Energy
Work done = Force × Distance
Pressure× Area
= P × A × L
If v = A × L then
= P× v
Force = F
Distance = L
Pressure = P
Area = A
Specific volume = v
Dr.Khaled S. Al-zahrani
Heat Energy
• Received +ve
• Rejected -ve
Work Energy
• Done By the fluid +ve
• Done On the fluid -ve
Q
+ve
-ve
W +ve
-ve
Dr.Khaled S. Al-zahrani
Rudolf Clausius (1822 – 1888)
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0th 1st
Closed System Open System
2ed 3ed
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Closed System:
Forms of energies:
Internal Energy U motion of Atoms
Kinetic Energy KE Movement
Potential Energy PE Elevation
Total Initial Energy Ei E1= U1 + K𝑬𝟏 + PE1
Total Final Energy Ef E2= U2 + K𝑬𝟐 + PE2
Conservation of energy law
Ei + Ee = Ef + El
Q W
U1 + Q = U2+W
Q = (U2 –U1) + W
Q - W = (U) Non-Flow Energy Equation
Dr.Khaled S. Al-zahrani
Examples:
U = ?
Q = +2500 Kj
W= +1400 Kj
From the 1st Law:
U = Q – W
= 2500 -1400
= +1100 kJ
The total energy is increasing
Dr.Khaled S. Al-zahrani
Examples:
Q = ?
= -700 Kj
Dr.Khaled S. Al-zahrani
Examples:
Q = ?
= -700 Kj
Dr.Khaled S. Al-zahrani
Examples:
W = ?
= +250 Kj/Kg
Dr.Khaled S. Al-zahrani
Examples:
U = ?
= +45 Kj/Kg
Dr.Khaled S. Al-zahrani
Examples:
Q = ?
= -120Kj/Kg
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