2. Thermodynamics-Definition
Thermodynamics is the branch of science which deals with the
study of energy, its transformation or conversion from one
form to another and its movement from one location to
another.
therme – means heat
dynamis – means force (strength)
4. Applications of Thermodynamics
▪Alternative energy systems
▪Solar-activated heating,
cooling, and power
generation
▪Geothermal systems
▪Ocean thermal, wave, and
tidal power generation
▪Wind power
▪Fuel cells
▪Thermoelectric and
thermionic devices
▪Magnetohydrodynamic
(MHD) converters
▪Biomedical applications
▪Life-support systems
▪Artificial organs
▪Power and Combustion systems
▪Automobile engines
▪Turbines
▪Compressors, pumps
▪Fossil- and nuclear-fueled power
stations
▪Propulsion systems for aircraft and
rockets
▪HVAC-Heating, ventilating, and air-
conditioning systems
▪Cryogenic systems, gas separation,
and liquefaction
▪Vapor compression and absorption
refrigeration
▪Heat pumps
▪Cooling of electronic equipment
6. Thermodynamics-Terminologies
System
-subject of the analysis
• Ex.free body or as complex,entire
chemical refinery,matter
contained within a closed, rigid-
walled tank, pipeline through
which natural gas flows.
Surroundings
-everything external to the system
Boundary
-separation between system and
surroundings
System Surroundings
Boundary
7. Thermodynamics-Terminologies
Closed System(Control Mass)
- it is defined when a particular
quantity of matter is under study.
- A closed system always contains the
same matter
- There can be no transfer of mass
across its boundary.
A special type of closed system that
does not interact in any way with its
surroundings is called an isolated
system.
10. Thermodynamics-Terminologies
Extensive Properties
-A property is called extensive if its value for an
overall system is the sum of its values for the
parts into which the system is divided.
-Extensive properties depend on the size or
extent of a system.
-Vary at most with time.
Ex.mass, volume, energy
11. Thermodynamics-Terminologies
Intensive Properties
-Their values are independent of the size or
extent of a system and may vary from place to
place within the system at any moment.
-May be functions of both position and time
Ex.Specific volume , pressure,and temperature
12. Thermodynamics- Terminologies
Volume(V)
-it refers to the volume of the working fluid in the
system
Internal Energy(U)
It is the energy stored within the body. It is the sum
of all the kinetic energies of all of its constituents
particles plus the sum of all the potential energies
of interaction among these particles
13. Thermodynamics- Terminologies
Enthalpy(H)
-It is the heat energy transferred to a substance at
a constant pressure process
H=U + PV
where H = Enthalpy
U= Internal Energy
P=Absolute Pressure
V= Volume
15. Thermodynamics-Terminologies
State
-refers to the condition of a system as described
by its properties.
-Since there are normally relations among the
properties of a system, the state often can be
specified by providing the values of a subset
of the properties.
Ex. Initial and Final states
16. Thermodynamics-Terminologies
Process
-It is a transformation from one state to another
i.e.,when any of the properties of a system
change, the state changes and the system is said
to have undergone a process.
-However,if a system exhibits the same values of its
properties at two different times, it is in the
same state at these times. A system is said to be
at steady state if none of its properties
changes with time.
Ex. Isobaric, Isothermal , Isochoric, Isentropic
processes
21. Thermodynamics-Terminologies
Pure substance
-uniform and invariable in chemical composition.
-can exist in more than one phase, but its chemical
composition must be the same in each phase.
For example, if liquid water and water vapor form
a system with two phases, the system can be
regarded as a pure substance because each
phase has the same composition.
A uniform mixture of gases can be regarded as a
pure substance provided it remains a gas and
does not react chemically.
22. Thermodynamics-Terminologies
• refers to a quantity of matter that is homogeneous throughout in both
• chemical composition and physical structure.
• Homogeneity in physical structure means that the matter is all solid, or
• all liquid, or all vapor (or equivalently all gas).
Phase
-
-
-A system can contain one or more phases.
Ex. a system of liquid water and water vapor (steam) contains
two phases.
-When more than one phase is present, the phases are separated by phase
boundaries.
oxygen + nitrogen = a single gas phase.
alcohol + water = a single liquid phase.
But liquids such as oil and water, which are not miscible, form
two liquid phases.
23. Phases of Water
Compressed Liquid - its pressure is greater than the
saturation pressure for the given temperature
Sub-cooled liquid – its temperature is less than the
saturation temperature for the given pressure
Saturated liquid – its temperature is equal to its
saturation temp., 100% liquid, 0% vapor
Saturated Mixture – temperature is equal to its saturation
temp., Y% liquid, X% vapor
Quality, X (dryness factor) – ratio of the
mass of vapor to the total mass of liquid and
vapor in the system
Saturated vapor – its temperature is equal to its
saturation temp., 0% liquid, 100% vapor
Superheated vapor – its temperature is greater that the
saturation temperature
Thermodynamics-Terminologies
25. Thermodynamics-Terminologies
Thermodynamic Cycle
-it is a sequence of processes that
begins and ends at the same
state.
-At the conclusion of a cycle all
properties have the same values
they had at the beginning.
-Consequently, over the cycle the
system experiences no net
change of state.
-Cycles that are repeated
periodically play prominent roles
in many areas of application.
Ex. Steam circulating through an
electrical power plant executes
a cycle.
26. Thermodynamic-Computations
Problems
1. An apple “weighs” 60 g and has a volume of 75
cm3 in a refrigerator at 8oC. What is the apple’s
density in kg/m3 and lbm/ft3? List 3 intensive
and 2 extensive properties of the apple.
2. One kilopond (1 kp) is the weight of 1 kg in the
standard gravitational field. How many Newtons
(N) is that? Pound force(lbf)?
3. At sea level, the weight of 1 kg mass in SI units is
9.81 N. What is the weight of 1 lbm mass in
English units?
27. Thermodynamic-Computations
Problems
4. A man goes to a traditional market to buy a steak for
dinner. He finds a 12-oz steak (1 lbm =16 oz) for
$3.15. He then goes to the adjacent international
market and finds a 320-g steak of identical quality
for $2.80. Which steak is the better buy?
5. The reactive force developed by a jet engine to push
an airplane forward is called thrust, and the thrust
developed by the engine of a Boeing 777 is about
85,000 lbf. Express this thrust in N and kgf.
