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:

Warning lamp
Fig. 44 Warning lamp in the instrument cluster First read and observe the introductory information and safety warnings Lights up or flashes Possible cause Solution The driver seat belt and, if the front passenger seat is occupied, the fr ...

Frequently asked questions
If you suspect that there is a fault in the vehicle or if your vehicle has been damaged, read and observe the following information before contacting a Volkswagen dealership or qualified workshop. You may also find useful information in the index under the headings Things to note or Checklist. ...

Service position for the front windscreen wipers
Fig. 74 Wiper blades in service position First read and observe the introductory information and safety warnings The windscreen wiper arms can be lifted off the windscreen when in the service position . Carry out the following steps to move the windscreen wipers to the service position: ...