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 ...

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Long-Term Underbody Protection -D 314 D36 M2-, Gray
Definition: Long-Term Underbody Protection -D 314 D36 M2-, Gray Edition 02/2010 Product description of Long-Term Underbody Protection -D 314 D36 M2-, gray Long-Term Underbody ...

Technical requirements
First read and observe the introductory information and safety warnings If the vehicle is supplied with a factory-fitted towing bracket it will already have the necessary technical modifications and meet the statutory requirements for towing a trailer. Only use a towing bracket that is appr ...

Checklist
Carry out the steps in the specified order : With the engine at operating temperature, park the vehicle on a level surface to ensure that the engine oil reading is correct. Switch off the engine and wait a few minutes for the engine oil to flow back into the sump. Open the ...