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:

Using the menus in the instrument cluster
Fig. 13 Vehicles without multifunction steering wheel: press button ① in the windscreen wiper lever to confirm the menu point and rocker switch ② to change the menu Fig. 14 Vehicles with multifunction steering wheel: control buttons for menus in the instrument cluster First read and ob ...

Maintenance Test, Performing
WARNING Do not check or charge batteries that have a visual indicator that is bright yellow. Jump starting must not be used! There is a risk of explosion during testing, cha ...

Introduction
This chapter contains information on the following subjects: → Seat heating Additional information and warnings: Adjusting the seat position Seat belts Airbag system Child seats (accessories) Exterior mirrors Luggage compartment WARNING Incorrec ...