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:

High Pressure Sensor -G65
Note For switching pressures, removing and installing switches and switch arrangement and version, see vehicle-specific refrigerant circuit. Refer to → Rep. Gr.87. ...

Service and disposal of belt tensioners
First read and observe the introductory information and safety warnings Seat belts may become damaged during any work on the belt tensioners or while removing or refitting any vehicle parts in conjunction with any other repair work. This damage will not always be noticeable. The consequence m ...

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: ...