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:

Unlocking the tailgate manually
Fig. 158 In the luggage compartment: manual release for the tailgate First read and observe the introductory information and safety warnings If necessary, fold the backrest of the rear bench seat forwards . Remove items of luggage so that you can reach the tailgate from the insid ...

Synchronising the vehicle key
First read and observe the introductory information and safety warnings It may no longer be possible to lock or unlock the vehicle with the remote control if the button is pressed repeatedly outside of the effective range of the vehicle key. If this is the case, the vehicle key ...

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 ...