Mechanisms of production of cold

Production of cold is accomplished by two well known mechanism,such as:
1.By evaporation
2.By heat transfer
Whenever a liquid evaporates it absorbs heat from its surroundings.The cooling of water in earthen pots of drinking purposes is the most common example of cooling by evaporation.
It is a known fact that heat always travel from hot place to a cold place.Since the heat energy travels from a hot space to a cold space,during this process hot space cools down and cold space heats up,This cooling by heat transfer.

Modes of heat transfer.

Heat is defined as the tranmission of heat energy from one region to another due to the temperature difference between these two regions.
Methods of heat transfer.
1.Condensation
It is a process of heat transfer from one particle of the body to another in the direction of fall of temperature.The particles remain in fixed position relative to each other.
2.Convection
It is a process of heat transfer from one particle of the body to another by convection current.The particles of the body move relative to each other.
3.Radiation
It is a process of heat transfer from a hot body to a cold body,in astraight line,without affecting the intervening medium.

Dear Home Air Conditioner Owner.

Refrigeration is defined as'process of reducing and maintaining the temperature of a body below the general temperature of its surroundings'
Thermodynamic State of Pure Substances
Generally a pure substance exists in the following three forms:
1.solid phase
2.Liquid phase
3.Vapour(or)gaseous phase
Water is taken as pure sustances.when ice melts there is a transformation of phase from solid to liquid.This is called melting (or) fusion of ice.Transformation can take place in the opposite direction from liquid to solid