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:

Wheel cover
Fig. 163 Removing press-on wheel covers Fig. 164 Removing bolted-on wheel covers First read and observe the introductory information and safety warnings Removing and fitting press-on wheel covers Take the box spanner and wire hook from the toolkit . Insert the wire hook into o ...

Ashtray in the drink holder
First read and observe the introductory information and safety warnings Fig. 104 Removable ashtray To use, place the removable ashtray in one of the drink holders in the front centre console or in the rear centre console . Opening and closing the ashtray To open, lift the ashtray cove ...

Service interval display
First read and observe the introductory information and safety warnings The service display is shown on the instrument cluster or . Service schedules at Volkswagen are divided into two categories, oil change service and inspections. The service interval display provides information on the n ...