AND DEVICES CLASS NOTES
In thermodynamics, meaning of ‘thermo’ is heat energy.
Dynamics means the motion of molecules or atoms.
Thermodynamic fluids are heat with fluids in motion.
Fluids are liquids, vapors & gases. Pressure, temperature,
specific volume, density, internal energy & specific weight
are important thermodynamic properties of fluids.
Thermodynamic properties which cannot be directly
measured are internal energy, entropy, enthalpy,
Helmholtz free energy and Gibbs free energy.
They are concepts to make the subject easy.
Calculate these from experimentally measurable properties.
Thermodynamics devices involve mass transfer,
energy transfer and both mass & energy transfer
Their study involves chemical reactions &
phase transformations, power consumption and power production.
Their use exists in heat transfer, combustion, fluid mechanics.
It uses laws of thermodynamics, Newton’s laws of motion,
laws of conservation of mass and steady flow energy equation.
Heat transfer deals with transfer of heat from
by conduction, convection & radiation.
Temperature gradient causes heat transfer. It deals
with heating, cooling, phase transformations and heat treatments.
Combustion deals with conversion of chemical
energy of fuels to heat energy. Energy gives
motion and work.
Fluid mechanics studies forces and their
effect on fluids. Study of fluids at rest
lies under fluid statics. Fluid dynamics include
kinematics and fluid kinetics. Fluid
kinematics deals with motion
of fluids. Fluid kinetics deals with motion
of fluids under forces acting on it.
Thermodynamics mainly dears with heat
and work conversions with fluids flow in various
thermodynamic devices. It considers a thermodynamic
system with boundary and surroundings.
Boilers, pumps and water turbines use water
Nozzles, steam engines, steam turbines & refrigerators use vapors.
Compressors and air conditioners use air
Different refrigeration systems use different refrigerants like R-22, R-134 a and R-717.
Fuel and air
Petrol, diesel, gas engines and gas turbines use fuel & air.
Steam engines, steam turbines & refrigeration system use steam as the working substance.
7. Other fluids
Heat exchangers use other fluids.
Fig. Simple vapor compression refrigeration cycle
(Fluid = refrigerant , device= refrigeration system)
Pump increases pressure of liquids using electrical energy.
Nozzles increase velocity at the expense of pressure energy.
Combustion chamber exists in internal combustion engines and gas turbines. This converts chemical energy of the fuels into heat energy.
Piston cylinder arrangement used in internal & external combustion engines. It produces mechanical and electrical power.
Pistons used in pumps and compressors consume electrical power to increase pressure.
Pressure vessels convert heat energy into pressure energy as in boilers.
Furnace converts chemical energy into heat energy.
Turbines convert kinetic energy into mechanical and electrical energies.
Turbo-compressors convert mechanical energy into pressure energy.
Diffusers convert kinetic energy into pressure energy. Turbo-compressors, jet engines and steam jet refrigeration system use diffusers.
Fans and blowers convert electrical energy into kinetic energy.
Wind mill coverts kinetic energy into mechanical and electrical energy.
Photo voltaic cells convert solar energy into electrical energy.
Human body converts chemical energy of foods into many other forms of energy. These energies are sound energy, mechanical energy, light energy and kinetic energy.
Throttle valve is constriction in a pipe to decrease pressure
Heat exchanger helps heat transfer from a hot fluid to a cold fluid.
Boiler converts liquid into vapors using heat.
Condenser converts vapors into liquid by losing heat.
Heat pump pumps heat from cold to hot regions.