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:

Positive and earth jump lead connection points
Fig. 190 In the engine compartment: jump lead connection point, positive ⊕ First read and observe the introductory information and safety warnings The positive jump lead connection point is in the engine compartment. In order to establish a suitable earth connection, screw towing eye into ...

Displays
Fig. 12 A: bonnet open, B: tailgate open, C: front left door open, D: right rear door open (only in four-door vehicles) First read and observe the introductory information and safety warnings Depending on the vehicle equipment level, a variety of information can be displayed in the instr ...

Driving through water on roads
First read and observe the introductory information and safety warnings Please follow these rules to help prevent damage to your vehicle when driving through water, for example if the road is flooded: Check the depth of the water before driving through it. The water level must be no hig ...