49
AH/AY-X08CR
AH/AY-X10CR
AH/AY-X13CR
1. Outline
1. 1 Refrigerant R410A
(1) Adoption of R410A in Air Conditioners
In 1974, it was pointed out that ozone layer in the upper stratosphere (about 20 ~ 40 km above ground) might
have been damaged by the ozone depleting substances such as CFC (chlorofluorocarbon) and HCFC
(hydrochlorofluorocarbon). Since that time, many countries across the world have endeavored to take
countermeasures against the ozone depletion.
As a refrigerant belonging to the HCFCs, the conventional refrigerant (R22) used in air conditioners also tends
to deplete the ozone layer. Therefore, complying with the provisions of the international regulations (i. e.
Montreal Protocol concerning the Ozone Depleting Substances) and national laws & regulations concerned, it
is necessary to replace R22-with other types of refrigerant which do not deplete the ozone layer.
A refrigerant composed of hydrogen (H), fluorine (F) and carbon (C), is called an HFC and does not deplete the
ozone layer. One HFC's is R410A whose pressure is about 1.6 times higher than R22 and whose energy
efficiency is almost comparable to that of R22 at the same refrigerant temperature.
(2) Chemical Characteristics of R410A
a) Chemical Stability
Like R22, R410A is a chemically stable, less toxic and not-flammable refrigerant. However, as in the case
of R22, the specific gravity of its vapour is larger than that of air and should it leak in an airtight room it may
stay at a low level and cause an oxygen starvation accident. It may also, should it come in direct contact
with file, cause a poisonous gas to occur, so be sure to handle it only in a well ventilated area.
Table 1. Comparison of Thermophysical Properties of R410 and R22
Composition (wt%)
R410A
R22
R32/R125 (50/50)
R22 (100)
72.6
86.5
- 51.4
- 40.8
1.56
0.94
64.0
44.4
Nonflammable
Nonflammable
0
0.055
1730
1700
Molecular weight
Boiling point (˚C)
Vapor pressure (25˚C, MPa)
Saturated vapor density (25˚C, kg/m
2
)
Inflammability
Ozone depletion potential (ODP)
Global warming potential (GWP)
Source: List of Thermophysical Properties complied by the Japan Sociery of Refrigeration
and Air Conditioning, NIST REFPROP V5.10, etc.
b) Composition Changes (Pseudo-azeotropic Characteristics)
R410A is a pseudo-azeotropic mixed refrigerant composed of two constituents-R32 and
R125. "Quasi-azeotropic" condition refers to a state in which the dew-point curve and boiling-point curve-
gas-liquid equilibrium curves (pressure constant) -almost lie on top of each other, and a multi-constituent
refrigerant having this chemical characteristic incurs less composition changes even when evaporation (or
condensation) as a phase change occurs. Consequently, even when refrigerant leaks from the gas phase
somewhere in the piping installation, the composition of circulated refrigerant incurs less changes.
Therefore, R410A can be treated in almost a same manner as a mono-constituent refrigerant like R22 is
treated. When actually charging R410A, however, do so from the liquid phase side by taking into account
the phenomenon that, when put in a cylinder, the composition changes a little between gas and liquid
phases.
C) Pressure Characteristics
As shown in Table 2, since R410A's
vapor-pressure is about 1.6 times
higher than that of R22 at the same
temperature, perform installation/
service with special toolsand
materials which are exclusive for
R410A and can withstand high
pressure.
Table 2. Comparison of Saturated Vapor Pressure of R410 and R22
Source: List of Thermophysical Properties complied by the
Japan Sociery of Refrigeration and Air Conditioning,
NIST REFPROP V5.10, etc.
Temperature (˚C)
Refrigerant
R410A
R22
0.30
0.14
0.70
0.40
1.35
0.81
2.32
1.43
3.73
2.33
4.15
2.60
- 20
0
20
40
60
65
