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:

Cleaning and changing windscreen wiper blades
Fig. 142 Variants A and B: Changing the windscreen wiper blades. Variants B and C: Changing the rear window wiper blade First read and observe the introductory information and safety warningsThe factory-fitted windscreen/window wiper blades are coated with graphite. The graphite coating ens ...

Autogas
Fig. 133 In the upper section of the centre console: switch for Autogas First read and observe the introductory information and safety warnings When the vehicle is restarted, the last manually selected operating mode will be adopted automatically. If, for example, autogas mode was activa ...

Start/stop system
Fig. 119 In the upper part of the centre console: button for the start/stop system First read and observe the introductory information and safety warnings If the start/stop system is activated, the engine will be switched off automatically when the vehicle is stationary. When required, t ...