Refrigeration & Equipment Engineering

Unit 1 - Fundamentals of Heat and Thermodynamics

1.8.Thermodynamics and Thermodynamics Laws
Thermodynamics is the science that deals with the relations between heat, work and properties of systems.General laws of energy transformation concerning all types of systems,mechanical,electrical and chemical may fall within the purview of this science.It is a science based on a number of empirical law formed by experimentation from which all predictions concerning the physical behaviour of the system may be deduced by logical reasoning.

Zeroth law of Thermodynamics
If two systems are both in thermal equilibrium with a third system, they are in thermal equilibrium with each other.

First law of Thermodynamics
Whenever a system undergoes a cyclic change the algebraic sum of work transfer is proportional to the algebraic sum of heat transfer or Heat and work are mutually convertible one into the other.

Second law of Thermodynamics
There is a definite limit to the amount of mechanical energy which can be obtained from a given quantity of heat energy.

Clausius statement of second law of Thermodynamics
It is impossible for a self acting machine working in a cyclic process, unaided by an external energy, to convey heat from a body at a lower temperature to a body at higher temperature.

Kelvin plank statement of second law of Thermodynamics
It is impossible to construct an engine, which while operating in a cycle produces no other effect except to extract heat from a single reservoir and do equivalent amount of work.