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:

Manual gearbox: selecting a gear
Fig. 110 Gear shift pattern of a 5 or 6-speed manual gearbox First read and observe the introductory information and safety warnings The positions of the individual driving gears are shown on the gearshift lever . Fully depress and hold the clutch pedal. Move the gear lever t ...

Masking or switching over headlights for driving abroad (travel mode)
First read and observe the introductory information and safety warnings If you have to drive a right-hand drive vehicle in a left-hand drive country, or vice versa, the asymmetric dipped beam headlights may dazzle oncoming traffic. Therefore, the headlights must be masked or switched over if ...

Severely Discharged Batteries
WARNING Risk of injury. Follow all Warnings and Safety Precautions. Refer to → Chapter „Warnings and Safety Precautions“. For a battery to be indicated as � ...