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:

Vehicle lifting points
Fig. 150 Lifting points at front for the lifting platform or vehicle jack Fig. 151 Lifting points at rear for the lifting platform or vehicle jack First read and observe the introductory information and safety warningsThe vehicle may only be lifted at the points shown in the illustration ...

Changing bulbs in the front headlights (Xenon)
Fig. 181 Rear view of right-hand Xenon headlight: ① cornering light and ② turn signal First read and observe the introductory information and safety warnings The headlight needs to be removed in order to change a bulb. The actions should only be carried ...

Windshield and Rear Window Washer System
The following hose connection types are used for connecting hoses to pumps and spray nozzles or as separating points – To loosen the connection, pulling both halves of the coupling apart. ...