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:

Insulating glass windscreen
Fig. 71 Metal-coated windscreen for infrared reflection with communication window (blue area) First read and observe the introductory information and safety warnings Insulating glass windscreens have a coating which reflects infrared radiation. There is a non-coated area above the interior ...

Introduction
This chapter contains information on the following subjects: → Making you and your vehicle safe → First aid kit and warning triangle Additional information and warnings: Braking, stopping and parking Manual opening and closing Vehicle toolkit Changing a ...

Closing the tailgate
Fig. 31 Open tailgate: handle recesses for closing the tailgate First read and observe the introductory information and safety warnings Closing the tailgate Grip one of the recesses in the interior trim of the tailgate . Pull the tailgate down with some force until it engages in th ...