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:

Mechanical controls on the front seats
Fig. 37 Front left seat controls with convenient entry function. Fig. 38 Front right seat controls without convenient entry function. First read and observe the introductory information and safety warnings Front left seat controls with convenient entry function The layout of the controls ...

Cleaning wheels
First read and observe the introductory information and safety warningsCleaning steel wheels An industrial cleaner is needed to remove accumulated brake dust. Steel wheels should therefore be cleaned regularly with a separate sponge. Any damage to the paint on steel wheels should be touched u ...

Belt height adjuster
Fig. 54 Next to the front seats: belt height adjuster First read and observe the introductory information and safety warnings The seat belt height adjusters for the front seats can be used to adjust the position of the seat belt on the shoulder so that it can be fastened properly: Pus ...