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:

Composite Wheels
Composite wheels consist of various parts. The primary components are rims and wheel discs. These components are fastened to each other with special screws and a special procedure. This ensures the wheel's function, proper seal, safety a ...

Water Content
Only very small amounts of water are soluble in liquid refrigerant. On the other hand, refrigerant vapor and water vapor mix in any ratio. Only a small drop of water may get into the refrigerant circuit. The dryer, dryer bag or dryer car ...

Evaporator Vent Temperature Sensor -G263- or Evaporator Temperature Sensor -G308
Function: The Evaporator Vent Temperature Sensor -G263- or Evaporator Temperature Sensor -G308- determines the temperature behind the evaporator. This value goes to the air conditioning control module and serves as a reference signal for ...