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This ppt describes you about some basics of thermal engineering.
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Fundamentals of THERMODYNAMICS
Introduction• Thermodynamics is science of energy transfer and its effects on
properties.
• Main aim is to convert disorganized form of energy into organized form of energy in an efficient manner.
• Based on the macroscopic approach which does not require knowledge of behavior of individual particles and is called classical thermodynamics.
System, Surroundings, and Boundary• A thermodynamic system is defined as quantity of matter or a
region in space chosen for study.
• The region outside the system is called surroundings.
• The real or imaginary surface that separates the system from its surroundings is called boundary.
• Universe = System + Surroundings
Types of System• Closed System
• Open System
• Isolated System
Closed System• A closed system consists of fixed amount of mass and no
mass may cross the system boundary but energy in form of heat and work may cross the system boundary.
• The closed system boundary may move.
• Examples of closed systems are sealed tanks and piston cylinder devices without valves.
Open System or Control Volume• An open system has mass as well as energy crossing the
boundary, called a control surface.
• Examples of open systems are pumps, compressors, turbines, valves and heat exchangers.
Isolated system• An isolated system is one in which there is no interaction
between the system and surroundings.
• It is of fixed mass and energy, and there is no mass or energy transfer across the system boundary.
• Examples of isolated system are universe and hot coffee in a well insulated flask.
Closed, Open, and Isolated Systems
Types of System
Energy Transfer
Mass Transfer
Examples
Closed System Yes No Gas in a sealed container
Open System Yes Yes Turbines, pumps, valves etc.
Isolated System
No No Universe, Thermoflask
Properties of a System• Any measurable characteristic of a system in equilibrium is called a
property.
• The property is independent of the path used to arrive at the system condition.
• Properties are point functions.
• Properties are exact differentials.
• Properties may be intensive or extensive.
Extensive Properties• Extensive properties depends on size or mass of the system.
• Some extensive properties are:
a. Mass
b. Volume
c. Total Energy
d. Electric Charge
e. Magnetization
Intensive Properties• Intensive properties are independent of size or mass of the system.
• Some intensive properties are:
a. Pressure
b. Temperature
c. Density
d. Velocity
e. Viscosity
Important points w.r.t Properties• Extensive properties per unit mass are intensive properties. For
example, the specific volume v, is defined as
v = = = = Intensive
• Specific Properties are intensive properties.
Thermodynamics Equilibrium A system is said to be in thermodynamic equilibrium if it maintains
a. Thermal Equilibrium ( Equality of Temperature )
b. Mechanical Equilibrium ( Equality of Forces / Pressure )
c. Chemical Equilibrium ( Equality of Chemical Potential )
State, Path, and Process• Condition of a system as defined by properties of system is known
as state of a system.
• Series of state of system through which process occurs is known as path of a system.
• Any change of state of a system is known as process.
• Some of the processes are-
Process Property held constant
Isobaric Pressure
Isothermal Temperature
Isochoric Volume
Isentropic Entropy
Thermodynamic cycle• A system is said to have undergone a cycle if the initial and final
points are same.
• Minimum number of processes required for a cycle are 2.
• For a cycle change in property is equal to zero.
Pure Substance• A substance is said to be a pure substance if it is
a. Homogeneous in Chemical Composition.
b. Homogeneous in Chemical Aggregation.
• Examples of pure substance are atmospheric air, steam-water mixture and combustion products of a fuel.
• Phase ( solid, liquid, gas ) is not considered while determining pure substance.