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:

Coolant specification
First read and observe the introductory information and safety warningsThe cooling system is filled at the factory with a mixture of specially prepared water and at least 40% coolant additive G 13 (TL-VW 774 J). The coolant additive is dyed purple. This mixture of water and coolant additive ...

Cleaning and caring for natural leather covers
First read and observe the introductory information and safety warningsPlease contact a Volkswagen dealership or other qualified workshop if you have any questions on cleaning and caring for the leather equipment in your vehicle. Care and use Natural leather is sensitive as it does not have ...

Coolant Fan Control Module -J293
Note Available in different construction styles, some installed on coolant fan -arrows-. This control module switches on and off the A/C clutch and therefore the A/C compressor. It switche ...