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Basic Thermodynamics

Basic Thermodynamics






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    Basic Thermodynamics Basic Thermodynamics Presentation Transcript

    • Introduction
    • Basic Thermodynamics Concepts
      • Heat.
      • System.
      • State.
      • Path .
      • Process.
      • Cycle.
      • Property .
    • Contd..
      • Process - Any change that a system undergoes from one equilibrium state to another is called a process .
      • Path - The series of state through which a system passes during a process is called a path
      • Cycle - A process with identical end states is called a cycle .
    • A review of basic thermodynamics: A refresher The ball represents mass exchange The arrow represents energy exchange
    • Zeroth Law of thermodynamics
      • The Zeroth Law deals with thermal equilibrium and provides a means for measuring temperatures.
      • Difference between thermal equilibrium and Thermodynamic equilibrium.
    • Zeroth Law of thermodynamics
    • First Law of thermodynamics
      • The first law is the law of conservation of energy.
      • The algebric sum of the work transfers is proportional to the algebric sum of heat transfer.
    • Limitations of First Law
      • It does not place any distinction on the direction of the process under consideration.
      • It will not help to predict, whether the system would undergo a change or no. It simply states that in a certain process heat and work are mutually convertible.
    • Second Law of thermodynamics
      • The Second law of clausis states that
      • It is impossible to construct a device that operates in a cycle and produces no effect other than the removal of heat from a body at one temperature and the absorption of an equal quantity of heat by a body at a higher temperature.
    • Second Law of thermodynamics contd..
      • The Second law of Max Planck’s states that
      • It is impossible to construct an engine working on a cyclic process whose sole purpose is to convert all the heat supplied to it into equivalent amount of work.
    • Few Examples
      • Some common examples.
      • All processes in nature occur unaided or spontaneously in one direction. But to make the same process go in the opposite direction one needs to spend energy.
    • Third Law of Thermodynamics
      • It is impossible by any procedure no matter how idealized, to reduce any system to the absolute zero temperature in a finite number of operations .
    • Summation of three laws
      • You can’t get something for nothing
              • To get work output you must give some thermal energy
      • You can’t get something for very little
              • To get some work output there is a minimum amount of thermal energy that needs to be given
      • You can’t get every thing
              • However much work you are willing to give 0 K can’t be reached.
    • Definitions of Reversible Process
      • A process is reversible if after it, means can be found to restore the system and surroundings to their initial states.
      • Some reversible processes:
      • Constant volume and constant pressure heating and cooling -the heat given to change the state can be rejected back to regain the state
    • Reversible Process (contd…)
      • Isothermal and adiabatic processes -the work derived can be used to compress it back to the original state.
      • Elastic expansion/compression (springs, rubber bands)
    • Some Irreversible Process
    • Thermodynamic Processes
      • A process in which the volume remains constant
      • constant volume process. Also called isochoric process / isometric process
      • A process in which the pressure of the system remains constant.
      • constant pressure process. Also called isobaric process
      • A process in which the temperature of the system is constant.
      • constant temperature process. Also called isothermal process
      • A process in which the system is enclosed by adiabatic wall.
      • Adiabatic process
    • Rankine Vapor power cycle
    • T-s diagram Rankine power cycle
    • P-V diagram Rankine power cycle
    • Rankine Cycle contd…
      • Process 1-2: Water from the condenser at low pressure is pumped into the boiler at
      • high pressure. This process is reversible adiabatic.
      • Process 2-3: Water is converted into steam at constant pressure by the addition of heat
      • in the boiler.
      • Process 3-4: Reversible adiabatic expansion of steam in the steam turbine.
      • Process 4-1: Constant pressure heat rejection in the condenser to convert condensate
      • into water.
      • The steam leaving the boiler may be dry and saturated, wet or superheated. The
      • corresponding T-s diagrams are 1-2-3-4-1; 1-2-3’-4’-1 or 1-2-3”-4”-1.
    • Thermal efficiency of rankine cycle
      • Consider one kg of working fluid, and applying first law to flow system to various processes with the assumption of neglecting changes in potential and kinetic energy, we can write,
      • δ q - δ w = dh
      • For process 2-3, δw = 0 (heat addition Process), we can write,
      • ( δ q )boiler= (dh )boiler =(h3-h2)