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:

After changing a wheel
First read and observe the introductory information and safety warnings Clean the tools as necessary and place them back in the toolbox in the luggage compartment . Stow the spare wheel, temporary spare wheel or the removed wheel safely in the luggage compartment. The tight ...

Changing bulbs in the side turn signals
Fig. 188 Removing the side turn signal bulb Fig. 189 Side turn signal: changing the bulb First read and observe the introductory information and safety warnings Depending on the vehicle, the side turn signal may be located in the front wing or in the exterior mirror . Please contact a ...

Checking with Expansion Valve and Receiver/Dryer, with Internally Regulated A/C Compressor
Note Connecting service station. Refer to → Chapter „Connecting Service Station“. Observe test requirements. Refer to → Chapter „Pressures, Checking“. – ...