Thermodynamics

Thermodynamics is very interesting subject in mechanical engineering. Check out ebooks, Notes and MCQs for thermodynamics below

  • A thermodynamic system is a region of space masked off by a boundary. A closed system is a fixed quantity of matter, where the boundary does not allow mass to be transferred in or out of the system, however work and heat can be. An open system allows mass to flow in and out, as well as incur heat and mass transfers.
  • Temperature, measured in Kelvins, 273 + Celsius. A thermistor can be used to determine temperature by measuring the electrical resistance flowing through – the higher the temperature, the higher the conductivity.
  • Pressure, force/area, measured in Pascals, Newton Metres, and Bar – where 1 bar = 10^5 Pa. By increasing the area, there is less pressure – snowshoes.
  • Atmospheric Pressure, force x weight of air above surface/unit area
  • Intensive properties do not depend on the mass of the substance within the system. Eg, Pressure, temperature, density.
  • Extensive properties depend upon mass. Eg, volume, internal energy, entropy, enthalpy.
  • Specific properties are reduced to unit mass of a substance to acquire the meaning of intensive properties, such as specific volume.
  • Equilibrium, when all parts of the system are at the same conditions.
  • Non-Equilibrium, when parts of the system are at different conditions. Irregularities and disturbances occur and propagate throughout the entire volume at finite velocity, leading to non-uniformity throughout the system.
  • Isothermal, constant temperature.
  • Isometric/Isochoric, constant volume.
  • Isobaric, constant pressure.
  • Adiabatic, Heat does not cross the system boundary.
  • A reversible process passes through a continuous series of states of equilibrium, where both working fluid and the surroundings are restored to their original state – an example of this would be an engine piston.
  • An irreversible process is a succession of non-equilibrium states, an example would be a burst membrane. Most real life processes are irreversible, however many can be approximated as reversible.
  • Work = Force x Distance
  • Equilibrium = Density X Area = Force + Pressure(atmosphere) x (A – Ao), where Ao is the piston rod area

On PV Diagrams:

  • A reversible expansion during which PV = Constant

images

  • Expansion larger volume than initial
  • Compression Smaller volume from initial
  • Reversible = Continuous Line
  • Irreversible = Dotted Line

Books for thermodynamics : –

Basic and Applied Thermodynamics by P.K.Nag pdf

 

Objective Questions for Thermodynamics

Thermodynamics MCQ with Answers – 2

Thermodynamic Mechanical Interview Questions And Answers