Volkswagen Golf Service & Repair Manual: Pressure and boiling point

Volkswagen Golf Service & Repair Manual / Air conditioning system with refrigerant R134a / General notes on air conditioning systems / Basics of air conditioning / Pressure and boiling point

The boiling points given in the table below are always based on an atmospheric pressure of 1 bar. If the pressure on a liquid is changed, its boiling point changes also.

It is well known that, for example, the lower the pressure, the lower the temperature at which water boils.

The vapour pressure curves for water and for refrigerant R134a show that at constant pressure and falling temperature the vapour becomes liquid (in the condenser), and that when pressure drops, the refrigerant changes from liquid into the vapour state (evaporator).

Vapour pressure curve for water

A -

Liquid

B -

Gaseous

C -	Vapour pressure curve for water

1 -	Pressure on the liquid in bar (absolute)

2 -	Temperature in °C

Pressure and boiling point

Vapour pressure curve for refrigerant R134a

A -

Liquid

B -

Gaseous

D -	Vapour pressure curve for refrigerant R134a

1 -	Pressure on the liquid in bar (absolute)

2 -	Temperature in °C

Pressure and boiling point

Heat always flows from warmer to colder material

Every material consists of a mass of moving molecules. The fast moving molecules of a warmer material loose part of their energy to slower molecules possessing less heat. This slows down the molec ...

Vapour pressure table for refrigerant R134a

The vapour pressure table for each refrigerant is published in the literature for refrigeration engineers. This table shows the vapour pressure exerted on the liquid ...

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