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:

Switching the TCS on and off
Fig. 116 In the centre console: button for switching the TCS on and off manually First read and observe the introductory information and safety warnings The electronic stability control (ESC) only functions when the engine is running. It consists of ABS, EDL and TCS. When the engine is r ...

Tires, Bringing to Mounting Temperature
Caution There is a risk of damaging tires with strong heat. Never heat the tires with a heater or a hot air gun. Warm tires with warm water or warm ...

Replacing the battery
Fig. 21 Vehicle key: opening the battery case cover Fig. 22 Vehicle key: removing the battery First read and observe the introductory information and safety warnings Volkswagen recommends having the battery changed at a Volkswagen dealership or by a qualified workshop. The battery is l ...