First Law of Thermodynamics - Application to closed systems (cyclic process)

 First law of thermodynamics states, "when a system undergoes a cyclic process, then the net heat transfer is equal to the net work transfer".

FIRST LAW OF THERMODYNAMICS - APPLICATION TO CLOSED SYSTEMS (CYCLIC PROCESS)

First law of thermodynamics states, "when a system undergoes a cyclic process, then the net heat transfer is equal to the net work transfer".

Mathematically,

It may be stated, "the heat and work are mutually convertible".

According to the law of conservation energy, "energy may be neither created nor destroyed but it can be transferred from one form to another form". In general, for any thermodynamic systems, the first law of thermodynamics can be written in the form of following equation.

Heat transfer = Work done + Change in internal energy

Q = W + ΔU            ….. (1.32)

It shows the first law of thermodynamics is based on the law of conservation of energy. 

The most common practical application of the First Law is the heat engines. When first law is applied to steady flow process, its applications include the following:

(a) Nozzles and diffusers (e.g. jet propulsion)

(b) Turbines (e.g. power plant, turbofan/turbojet aircraft engine), compressors and pumps (power plant)

(c) Heat exchangers (e.g. boilers and condensers in power plants, evaporator and condenser in refrigeration, food and chemical processing)

(d) Throttling devices (e.g. refrigeration, steam quality measurement in power plants)