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

...

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:

Notes on tow-starting
First read and observe the introductory information and safety warnings Vehicles should not be tow-started wherever possible. Use jump leads to start the engine instead . For technical reasons, the following vehicles cannot be tow-started: Vehicles with an automatic gearbox. If ...

Adjusting the head restraints
Fig. 39 Adjusting front head restraint Fig. 40 Adjusting rear head restraint First read and observe the introductory information and safety warnings Every seat is fitted with a head restraint. The centre rear head restraint is designed solely for use with the centre rear seat. This head r ...

Replacing Reservoir, No Contaminants, No Loss of Refrigerant
Discharge the refrigerant circuit. – Replace the restrictor depending on the vehicle. – Remove receiver or accumulator. – Remove dirt from receiver or res ...