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:

Indicator lamps
First read and observe the introductory information and safety warnings Lit up Possible cause Solution Engine management system fault (Electronic Power Control). The engine should be checked by a qualified workshop as s ...

Opening and closing the bonnet
Fig. 134 A: release lever in the footwell on the driver side. B: release lever on the bonnet Fig. 135 C: holder for the bonnet stay in the lock carrier. D: bonnet secured with the bonnet stay First read and observe the introductory information and safety warningsOpening the bonnet Ensu ...

Acoustic and optical ParkPilot signals at the rear of the vehicle
Fig. 121 ParkPilot screen display (colour) Fig. 122 ParkPilot screen display (monochrome) First read and observe the introductory information and safety warnings Key for displays and Meaning Ⓐ Scanned area ...