Service guide | Application, Installation and Maintenance Manual MCHE
5
AX292455807588en-000101 | 01.2019 |
Consider the following during bending:
•
MCHEs are constructed of soft aluminum
and are susceptible to deformation during
handling . Prior to bending operation, make
sure the MCHE is flat, square and undam-
aged . Consider a sizing operation to ensure
this .
•
Make sure the coils are loaded into the
bender in a way that keeps them flat square
and undamaged .
•
Keep the flat tubes perpendicular to the
spindle while bending the coil .
•
Clamp the coil during the bending process,
being careful not to crush it .
•
Slower bending speeds will often yield
better results .
•
Vertical spindle bending machines are often
set up so that the microchannel coil ends up
sliding along the table with all its weight
supported by the header ends and/or the
bottom dead tube .
During the bending operation, do not let
one end of the coil become cantilevered off
the edge the table, because this can cause
the coil to droop with the tubes being
non-perpendicular to the spindle, resulting
in corkscrewing or reduced bend quality
and/or consistency . Note that with some
benders, a portion of the supporting table
will drop down during bending, creating
opportunities for cantilever loads and
improper bending .
•
Bending multi-bend coils on a horizontal
spindle bender can cause cantilevered
loads resulting from the dead weight of the
unsupported bent legs . As an example, a
coil with three (3) bends, depending on
fixturing, may result in the load of the first
75% of the coil being transferred into the
remaining coil leg, possibly causing poor
bend quality and/or permanent deforma
tion . Bending challenges are greater with
MCHE’s than similar fin and tube coils,
requiring proper fixturing .
3. Installation
3.1 Pass arrangement
Carefully identify the locations of the inlet and
outlet tubes . Microchannel condensers is often
designed with multiple passages (parallel flow)
that have fewer tubes in each successive pass
(Fig . 2)
Danfoss MCHEs include a small notch in both
headers to indicate that this is the bottom of the
heat exchanger . Additionally, a product label is
placed on the outermost tube (unless specified
elsewhere by the customer), indicating the top of
the heat exchanger .
Incorrectly connecting the inlet and outlet tubes
of a MCHE will likely result in excessive refrige-
rant side pressure drop and poor heat transfer .
Fig . 2 MCHE passes distribution
3.2 Fan location and size
Air distribution may have an influence on the
performance of the MCHE . For good air distribu-
tion choosing a fan with proper fan diameter and
keeping a constant distance between the coil
and the fan is desirable . We recommend
selecting a fan diameter that is as close as
possible to the smallest of MCHE height and
length . The distance between MCHE and fan is
)
recommended to be at least 15 times the width/
depth of MCHE coil when possible (Fig .3) .
MCHE
Fan Installation Face
H
L
Disstance
Fig . 3 Fan location and size
Outlet
Few tubes
Inlet
Many tubes
2
3
4
