fundamentals of thermodynamics
DESCRIPTION
This ppt describes you about some basics of thermal engineering.TRANSCRIPT
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Fundamentals of THERMODYNAMICS
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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.
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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
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Types of System• Closed System
• Open System
• Isolated System
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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.
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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.
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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.
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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
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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.
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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
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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
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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.
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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 )
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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
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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.
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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.