Technical
from the single-component HFC refrigerant R134a, these are
mainly blends (different compositions) of the components
R32, R125, R134a, R143a, and R600(a).
The following description mainly concerns the
development and potential applications of these. The
halogen-free substitutes NH 3
, propane and propylene as well
as CO 2
should also be considered, however, specific criteria
must be applied for their use. In addition, R32 and HFO/HFC
blends can also be used as alternatives.
R407C AS SUBSTITUTE FOR R22
Mixtures of HFC refrigerants R32, R125 and R134a were
considered to be the preferred candidates for short-term
substitutes for R22 in the EU in view of the early ban of R22.
Performance values and efficiency are highly comparable
(Figure 19**). At first two blends of the same composition
have been introduced under the trade names AC9000*
(DuPont) and KLEA 66* (ICI). They are listed in the ASHRAE
nomenclature as R407C. In the meantime, there are also
further blend varieties (for example R407A/R407F/R407H)
with somewhat differing compositions, whose properties
have been optimised for particular applications. The
substitutes for R22 in air conditioning systems and heat
pumps under consideration contain higher proportions of
R32 and R134a. A good correspondence with the properties
of R22 in terms of pressure levels, mass flow, vapour density
and volumetric refrigerating capacity is thus achieved. In
addition, the global warming potential is relatively low (GWP
=1774), which is a good presupposition for favourable Total
Equivalent Warming Impact (TEWI) values.
Thus, R407C also complies with the requirement of the
new European Union (EU) F-Gas Regulation which from
2020 onwards will only allow refrigerants with GWP < 2500.
However, the quantity limitation through the ‘phase-down’
will also lead to significantly restricted availability.
The high temperature glide is a disadvantage for usual
applications which requires appropriate system design and
can have a negative influence on the efficiency of the heat
exchangers.
Due to the properties mentioned, R407C is preferably
an R22 substitute for air conditioning and heat pump
systems and (within certain limitations) also for medium
temperature refrigeration. In low temperature refrigeration,
because of the high proportion of R134a, a significant drop in
refrigerating capacity and coefficient of performance (COP)
is to be expected. There is also the danger of an increased
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RACA Journal I August 2020
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