Volkswagen Polo Service & Repair Manual: Pressure and Boiling Point

Volkswagen Polo Service & Repair Manual / Refrrigerant R134a Servicing / A/C System, General Information / 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 boiling point also changes.

For example, water boils at a lower temperature the lower the pressure.

The vapor pressure curves for water and refrigerant R134a show that, at constant pressure, reducing the temperature changes vapor to liquid (in the condenser) or that reducing the pressure causes the refrigerant to change from liquid to vapor (evaporator).

Vapor pressure curve of water

A -

fluid

B -

Gaseous

C -	Vapor pressure curve of water

1 -	Pressure acting on liquid in bar (psi)

2 -	Temperature in °C (°F)

Pressure and Boiling Point

Vapor pressure curve of refrigerant R134a

A -

Fluid

B -

Gaseous

D -	Vapor pressure curve of refrigerant R134a

1 -	Pressure acting on liquid in bar (psi)

2 -	Temperature in °C (°F)

Pressure and Boiling Point

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