lec 02 15042013
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IntroductionThermodynamics is derived from two words:
‘Thermo’ which means ‘Heat energy’ and ‘Dynamics’ which means ‘conversion’ or ‘transformation’
Concisely, thermodynamics is a division of science that deals with conversion of energy from one form to another
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DefinitionsThermodynamics is the science of the
relationship between heat, work, and systems that analyze energy processes.
Conservation of energy principle. It simply states that during an interaction, energy can change from one form to another but the total amount of energy remains constant. That is, energy cannot be created or destroyed.
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DefinitionsTemperature is indicator of direction for heat
flow. It doesn't refer to the internal thermal energy of a system.
Temperature describes the tendency of an object to give up energy to it's surroundings.
Heat is defined as the form of energy that is transferred between two systems by virtue of a temperature difference.
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DefinitionsThe change in the energy content of a body or any
other system is equal to the difference between the energy input and the energy output, and the energy balance is expressed as Ein - Eout = E.
Macroscopic approach to the study of thermodynamics that does not require a knowledge of the behavior of individual particles is called classical thermodynamics.
Average behavior of large groups of individual particles, is called statistical thermodynamics.
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Applications Of ThermodynamicsI.C EnginesPower PlantsHeat TransferRefrigeration Energy Efficient Buildings
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Systems and Control VolumeA system is defined as a quantity of matter or a
region in space chosen for study.. The mass or region outside the system is called
the surroundings.The real or imaginary surface that separates the
system from its surroundings is called the boundary. The boundary of a system can be fixed or movable.
A boundary is a closed surface surrounding a system through which energy and mass may enter or leave the system.
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Systems and Control VolumeA closed system (also known as a control
mass) consists of a fixed amount of mass, and no mass can cross its boundary. But it permits transfer of energy in the form of heat or work across the boundary. If neither mass or energy allowed to cross the boundary, that system is called an isolated system.
An isolated system is one with rigid walls that has no communication (i.e., no heat, mass, or work transfer) with its surroundings.
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Systems and Control VolumeA Open system (also known as a control
volume) is one in which both mass and energy cross the boundary.
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PROPERTIES OF A SYSTEMAny characteristic of a system is called a
property.Intensive properties are those that are
independent of the mass of a system.Extensive properties are those whose values
depend on the size or extent of the system such as proportional to mass of system.
Extensive properties per unit mass are called specific properties.
A continuous, homogeneous matter with no holes, that is, a continuum.
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Density and specific gravityDensity is defined as mass per unit volume.The reciprocal of density is the specific
volume v, which is defined as volume per unit mass.
Specific gravity or relative density is ratio of the density of a substance to the density of some standard substance at a specified temperature.
The weight of a unit volume of a substance is called specific weight.
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State and EquilibriumEach unique condition of system is called
state.In an equilibrium state there are no
unbalanced potentials (or driving forces) within the system.
The system will be in thermal equilibrium if its temperature is same throughout the system.
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Figure1: A closed system reaching thermal equilibrium
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State and EquilibriumMechanical equilibrium is related to
pressure, and a system is in mechanical equilibrium if there is no change in pressure at any point of the system with time.
If a system involves two phases, it is in phase equilibrium when the mass of each phase reaches an equilibrium level and stays there.
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State and EquilibriumA system is in chemical equilibrium if its
chemicalcomposition does not change with time,
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