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

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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:

Variable luggage compartment floor
Fig. 86 A: variable luggage compartment floor folded up and secured; B: expanding luggage compartment to front Fig. 87 C: extending the luggage compartment down; D: setting the maximum luggage space First read and observe the introductory information and safety warnings The luggage compar ...

Improvised Tools
Note This list outlines the testers, tools and materials required for expert refrigerant circuit repair work. Caution Non-approved tools or materials such as leak sealing additiv ...

Removing and fitting head restraints
First read and observe the introductory information and safety warnings Every seat is fitted with a head restraint. The centre rear head restraint is designed solely for use with the centre rear seat. This head restraint should therefore not be installed in any of the other positions. Remov ...