Thermodynamic system and control volume :

A Thermodynamic system is defined as a “quantity of matter or a region in space upon which attention is concentrated in the analysis of a problem“.

The system is separated from the surroundings by the system boundary. The boundary may be either fixed or moving. A system and its surroundings together comprise a universe. Everything external to the system is called the surroundings or the environment.

Thermodynamic Equilibrium: A system is said to exist in a state of thermodynamic equilibrium when no change in any macroscopic property is registered if the system is isolated from its surroundings.

A system will be in a state of thermodynamic equilibrium if the conditions for the following three types of equilibrium are satisfied:

a) Mechanical equilibrium

b)Chemical equilibrium

c) Thermal equilibrium

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  • Isolated system: Internal Energry of system remain constant if no work. [...Fixed mass, Fixed energy]
  • Displacement work:
    • (dw=pdv) whereas dQ=dU+dw
    • here dQ is energy
  • First law of Thermodynamics:
    • For a closed system undergoing a cycle. ⌠dq=⌠dw
    • For a closed system undergoing a change of state. Q=Δu+w
    • Cv=(∂u∕∂T)r=(∂Q∕∂T) & Cp=(∂h∕∂T)p=(∂Q∕∂T)p where as [CP-CV=R]
    • For polytropic process the specific heat is Cn=Cv(r-n/1-n)
  • First law appiled to Flow Process:
    • steady flow process :
    • mi=m0 where as ==> A1C1/V1=A2C2/V2
    • Variable flow process :
    • mi-mo=mv
    • workdone in flow process = –12vdp [...Q=Δh-12vdp]
  • Second law of thermodynamics:
    • Efficiency of heat engine . n=Q1-Q2/Q1=Wnet/Q1 <100%

For more detailed information about thermodynamics formulas and definitions and examples..Thermodynamics – Simple English Wikipedia, the free encyclopedia

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