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:

Fiber-Optic Cable, Assembling
Special tools and workshop equipment required Fiber-Optic Conductor Repair Set -VAS6223A- Hose Cutting Pliers -VAS6228- Vehicle Diagnostic Tester It is very diffi ...

Wheel bolts
Fig. 166 Changing a wheel: loosening the wheel bolts Fig. 167 Changing a wheel: anti-theft bolt and adapter First read and observe the introductory information and safety warnings Only the spanner delivered with the vehicle should be used to loosen the wheel bolts. Only loosen the whee ...

Welding and Soldering on Refrigeration Systems
Before performing welding or soldering work on vehicles near the air conditioning system components, extract the refrigerant and remove the residue by flushing with compressed air and nitrogen. The products of refrigerant decomposition d ...