Technical
be used to some extent because of the good solubility of the
hydrocarbon constituent. However, in systems with a high
oil circulation rate or a large volume of liquid in the receiver,
oil migration may result. In such cases, additional measures
are necessary.
Due to the high global warming potential (GWP ≥
2500), R417B and R422D will no longer be allowed for new
installations in the EU from 2020. The requirements and
restrictions are specified in the F-Gas Regulation 517/2014.
However, the ‘phase-down’ quantity limitation will also lead
to significantly restricted availability of R417A and R438A.
R427A AS A SUBSTITUTE FOR R22
This refrigerant blend was introduced some years ago under
the trade name Forane FX100 (Arkema) and is now listed in
the ASHRAE nomenclature as R427A.
The R22 substitute is offered for the conversion of
existing R22 systems for which a ‘zero ODP’ solution is
requested. It is an HFC mixture with base components R32/
R125/R143a/R134a. In spite of the blend composition based
on pure HFC refrigerants, the manufacturer states that a
simplified conversion procedure is possible. This is facilitated
by the R143a proportion.
Accordingly, when converting from R22 to R427A, all
it takes is a replacement of the original oil charge with
ester oil. Additional flushing sequences are not required,
as proportions of up to 15% of mineral oil and/or alkyl
benzene have no significant effect on oil circulation in the
system. However, it must be taken into account that the
highly polarised mixture of ester oil and HFC will lead to
increased dissolving of decomposition products and dirt in
the pipework. Therefore, generously dimensioned suction
clean-up filters must be provided.
Regarding refrigerating capacity, pressure levels, mass
flow and vapour density, R427A is relatively close to R22.
During retrofit, essential components such as expansion
valves can remain in the system. Due to the high proportion
of blend components with low adiabatic exponent, the
discharge gas temperature is considerably lower than with
R22, which has a positive effect at high compression ratios. It
must be taken into account that this is also a zeotropic blend
with a distinct temperature glide. Therefore, the criteria
described for R407C apply here as well.
The following report deals
with potential measures of a
short- to medium-term change
towards technologies with
reduced environmental impact
in medium and large size
commercial refrigeration and air
conditioning systems.
R427A meets the requirement of the EU F-Gas Regulation,
which will only allow refrigerants with GWP < 2500 from
2020. However, the quantity limitation due to the ‘phasedown’
will also lead to significantly restricted availability.
R32 AS SUBSTITUTE FOR R22
As described earlier, R32 belongs to the HFC refrigerants,
but initially it was mainly used as a component of refrigerant
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