Prevention Of Galvanic Corrosion - Danfoss MCHE Installation And Maintenance Manual

Service guide | Application, Installation and Maintenance Manual MCHE
Plastic heat shrink tubing prevents galvanic
corrosion in the MCHE's copper to aluminum
joint by keeping moisture from entering the area.
A minimum of 70mm length from the Cu/Al joint
to the connection point is required to protect the
Cu-Al brazing joint and plastic shrink tube from
excessive heat during the brazing process. When
brazing copper piping to the MCHE, it is recom-
mended to use dry nitrogen purging along with
a heat sink and/or wrapping the copper stub
tube with a wet cloth to protect the Cu/Al joint
and heat shrink tubing from excessive heat. This
L≥70 mm
also applies to microchannel heat exchangers
with aluminum inlet/outlet tubes. Depending on
the location of the connections relative to the
heat exchanger, a heat shield may be required to
protect the MCHE's tubes and fins from the
brazing torch. The recommended pipe length
"L" after the brazing joint should be greater than Fig. 7 Recommended length of inlet/outlet
or equal to 70mm as shown in the picture below connections
(Fig.7).
3.4 Elimination of gaps
To maximize heat transfer performance, gaps
should be eliminated on both sides of the face of
the MCHE. Gaps should also be eliminated on
the top, bottom and sides of the MCHE so that all
fan induced air is directed over the coil surface.
This can be accomplished with sealing strips as
shown in Fig. 8.
Fig. 8 Typical installation

3.5 Prevention of galvanic corrosion

Aluminum is a chemically reactive metal and will
corrode when combined with most metals that
are used today in industrial manufacturing. To
avoid any galvanic corrosion, it is necessary to
separate Al and other metals. The best way to
prevent galvanic corrosion is to use plastic/
rubber/foam as a means to isolate the aluminum
coil from dissimilar metals (Fig 8)
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