Volkswagen Polo Service & Repair Manual: Physical Principles

Volkswagen Polo Service & Repair Manual / Refrrigerant R134a Servicing / A/C System, General Information / A/C Technology Basic Principles / Physical Principles

The four known states of water also apply to air conditioning system refrigerants.

1 -	gaseous (invisible)

2 -

vapor

3 -

fluid

4 -

solid

Physical Principles

When water is heated in a vessel (heat absorption), water vapor can be seen to rise. If the vapor is further heated through heat absorption, the visible vapor turns into invisible gas. The process is reversible. The warmth is extracted from gaseous water, vapor forms first, then water and then ice.

A -	Heat absorption

B -	Heat emission

Physical Principles

Heat Transfer

Every substance consists of a mass of moving molecules. The fast moving molecules of a warmer substance give off some of their energy to the cooler and thus slower molecules. As a result, the molecular motion of the warmer substance slows down and that of the colder substance is accelerated. This process continues until the molecules of both substances are moving at the same speed. They are then at the same temperature and no further heat exchange takes place.

A/C Technology Basic Principles

...

Pressure and Boiling Point

The boiling point given in tables for a liquid is always referenced to an atmospheric pressure of 1 bar (14.5 psi). If the pressure acting on a fluid changes, its boi ...

Other materials:

Pressure Gauge, Tests and Measurements
Indicators on pressure gauge 1 - Temperature scale for refrigerant R134a CF3–CH2F or CH2F–CF3. 2 - Pressure scale The pressure gauge may have one or more temperature s ...

Cleaning wheels
First read and observe the introductory information and safety warningsCleaning steel wheels An industrial cleaner is needed to remove accumulated brake dust. Steel wheels should therefore be cleaned regularly with a separate sponge. Any damage to the paint on steel wheels should be touched u ...

Engine oil specification
First read and observe the introductory information and safety warningsThe engine oil used must correspond exactly to specifications. The correct engine oil is important for the function and service life of the engine. A special high quality multigrade oil has been filled at the factory and t ...