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 ...

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Checklist
To ensure your own safety and that of your passengers, observe the following actions in the specified order : Stop the vehicle at a safe distance away from moving traffic and on a suitable surface . Switch on the hazard warning lights using the button . Apply the handbrake ...

A/C System Operation
The temperature in the passenger compartment depends on the amount of heat radiated through the windows and conducted by the metal parts of the body. In hot weather it is possible to achieve a more comfortable temperature for the passengers by pumping of ...

Anti-theft alarm
First read and observe the introductory information and safety warnings Depending on the vehicle equipment level, the vehicle may have an anti-theft alarm and a SAFELOCK mechanism . The anti-theft alarm makes it more difficult to break into the vehicle or steal it. The anti-theft alarm is ...