Get Technical data Basic technical and physical properties -> 6.1 Basics of air conditioning technology Guide for Volkswagen Sharan VAN Second Generation (2010-2023)

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

Basic technical and physical proper‐

ties

⇒ “6.1 Basics of air conditioning technology”, page 16

⇒ “6.2 Physical properties”, page 19

⇒ “6.3 Produccharacteristics”, page 26

⇒ “6.4 Function and role of air conditioning system”, page 26

⇒ “6.5 Other reference material”, page 28

6.1

Basics of air conditioning technology

⇒ “6.1.1 Physical properties of air conditioning system”,

page 16

⇒ “6.1.2 Pressure and boiling poinof refrigerant”, page 17

⇒ “6.1.3 Vapour pressure table for refrigerant”, page 17

⇒ “6.2 Physical properties”, page 19

6.1.1

Physical properties of air conditioning

system

The 4 familiar states of water apply to air conditioning refrigerants

as well.

1 - Gas (invisible)

2 - Vapour

3 - Liquid

4 - Solid

When water is heated in a vessel (heaabsorption), water vapour

can be seen to rise. If the vapour is heated by further heaab‐

sorption, the visible vapour becomes invisible gas. The process

is reversible. If heais extracted from gaseous water -A-, i

changes firsto vapour -B-, then to water and finally to ice.

A - Heaabsorption

B - Headissipation

Heaalways flows from a warmer to a colder substance

Every substance consists of a mass of moving molecules. The

fasmoving 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

thaof the colder substance is accelerated. This continues until

the molecules in both materials are moving athe same speed.

They are then athe same temperature and no further heaex‐

change takes place.

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

6.1.2

Pressure and boiling poinof refrigeran

The boiling poingiven in tables for a liquid is always referenced

to atmospheric pressure (1 bar absolute pressure). If the pressure

over a fluid changes, its boiling poinchanges as well.

Note

Pressure is indicated in various units: 1 MPa (Mega-Pascal) is

equal to 10 bar or 145 psi; 1 bar absolute pressure is equal to

0 bar, which is abouthe same as ambienpressure (atmospheric

pressure).

Iis well known thae.g. the lower the pressure, the lower the

temperature awhich water boils.

The vapour pressure curves for water and for R1234yf refrigeran

show thaaconstanpressure and falling temperature the vapour

becomes liquid (in the condenser), and thawhen pressure drops,

for example, the refrigeranchanges from liquid into the vaporous

state (in the evaporator).

Vapour curve, water

A - Liquid

B - Gaseous

C - Vapour curve, water

1 - Pressure on the liquid in bar (absolute)

2 - Temperature in °C

Vapour pressure curve for refrigeranR1234yf

A - Liquid

B - Gaseous

D - Vapour pressure curve for refrigeranR1234yf

1 - Pressure on the liquid in bar (absolute)

2 - Temperature in °C

Note

The vapour pressure curves of both refrigerants, R1234yf and

R134a, are very similar across a broad temperature range. The

pressure difference between the two refrigerants in a temperature

range of 0 C to +50°C is only abou0.2 bar, for example, which

is why iis nopossible to differentiate between the two refriger‐

ants ⇒ “6.1.3 Vapour pressure table for refrigerant”, page 17

and ⇒ Air conditioning system with R134a refrigerant; Rep. gr.

87 ; General information abouthe air conditioning system and

refrigerancircui. Iis only possible to determine a difference

using relevansensors, which can analyse the chemical structure

of the refrigeran

⇒ “6.2.16 Analysis of refrigeranR1234yf”, page 24 .

6.1.3

Vapour pressure table for refrigeran

The vapour pressure table for every refrigeranis published in

literature for refrigeration system engineers. This table makes i

6. Basic technical and physical properties

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

possible to determine the vapour pressure acting on the column

of liquid in a vessel if the temperature of the vessel is known.

Since its own characteristic vapour pressure table is known for

each refrigerant, iis possible to establish the type of refrigeran

by measuring the pressure and temperature of refrigerants whose

vapour pressure changes over a certain temperature range (does

noapply when differentiating between R1234yf and R134a as

the vapour pressures are too close

⇒ “6.1.2 Pressure and boiling poinof refrigerant”, page 17 ).

Note

♦ The means of differentiation are only given for pure refriger‐

ants whose vapour pressures differ sufficiently. If differen

refrigerants are mixed for form a new refrigeran(e.g. 3 differ‐

enrefrigerants to form R407C refrigerant), a vapour pressure

will be created in accordance with the vapour pressures of the

individual refrigerants and their percentage in the mixture.

♦ Absolute pressure means tha“0 bar” corresponds to an ab‐

solute vacuum. The normal ambienpressure corresponds to

“1 bar” absolute pressure. On mospressure gauges, a read‐

ing of “0 bar” corresponds to an absolute pressure of one bar

(which is confirmed by the existence of a “-1 bar” marking be‐

neath the “0” scale marking).

♦ Pressure is indicated in various units: 1 MPa (Mega-Pascal)

is equal to 10 bar or 145 psi; 1 bar absolute pressure is equal

to 0 bar, which is abouthe same as ambienpressure (at‐

mospheric pressure).

♦ The vapour pressures of the two refrigerants, R1234yf and

R134a, are very similar across a broad temperature range,

which is why no difference can be established between them

⇒ Air conditioning system with R134a refrigerant, General in‐

formation abouthe air conditioning system . Iis only possible

to determine a difference using relevansensors, which can

analyse the chemical structure of the refrigeran

⇒ “6.2.16 Analysis of refrigeranR1234yf”, page 24 .

Temperature in °C

Pressure in bar (positive pres‐

sure) R1234yf

-40

-30

-25

-20

-15

-10

-5

-0.40

-0.01

0.12

0.50

0.83

1.21

1.65

2.15

2.72

3.36

4.09

4.90

5.81

6.82

7.93

9.17

10.52

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Air conditioning systems with refrigeranR1234yf - General information - Edition 07.2017

Temperature in °C

Pressure in bar (positive pres‐

sure) R1234yf

12.01

13.64

15.41

17.35

19.46

21.75

24.24

26.94

29.09

6.2

Physical properties

⇒ “6.2.1 R1234yf refrigerant”, page 19

⇒ “6.2.2 Potential risks with R1234yf refrigerant”, page 20

⇒ “6.2.3 Physical and chemical properties of R1234yf refrigerant”,

page 20

⇒ “6.2.4 Critical point”, page 20

⇒ “6.2.5 Environmental aspects of refrigeranR1234yf”,

page 21

⇒ “6.2.6 Trade names and designations of R1234yf refrigerant”,

page 21

⇒ “6.2.7 Colour and odour of R1234yf refrigerant”, page 22

⇒ “6.2.8 Vapour pressure of R1234yf refrigerant”, page 22

⇒ “6.2.9 Physical properties of R1234yf refrigerant”, page 22

⇒ “6.2.10 How R1234yf refrigeranreacts to metals and plastics”,

page 22

⇒ “6.2.11 Critical temperature / critical pressure of R1234yf re‐

frigerant”, page 23

⇒ “6.2.12 Water contenof R1234yf refrigerant”, page 23

⇒ “6.2.13 Flammability / decomposition of R1234yf refrigerant”,

page 23

⇒ “6.2.14 Charge factor of refrigeranR1234yf”, page 23

⇒ “6.2.15 Evidence of leaks in a refrigerancircuiwith R1234yf

refrigerant”, page 24

⇒ “6.2.16 Analysis of refrigeranR1234yf”, page 24

⇒ “6.2.17 Returning contaminated R1234yf refrigeranfor analy‐

sis, processing or disposal”, page 25

6.2.1

R1234yf refrigeran

♦ Air conditioners in vehicles employ the evaporation and con‐

densation process. A substance (the refrigerant) is moved

aboua circuiwithin an enclosed system.

♦ The substance is one thahas a low boiling point, in this in‐

stance R1234yf refrigerant.

♦ The R1234yf refrigeranis marketed under various names

(e.g. HFO 1234yf, Opteon 1234yf etc.).

6. Basic technical and physical properties

Technical data Basic technical and physical properties -> 6.1 Basics of air conditioning technology for Your Volkswagen Sharan VAN Second Generation (2010-2023)

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