**Don't** use "suction ring!! This is a piece of **surgical** equipment!!!! See Google search results at:

http://www.google.com/search?q="suction ring"

I think this must be a "low pressure coil"

From LGDT:

plomberie
tuyauterie
Anglais:
coil (a)
Note(s): ((Dans la source citée, l'entrée se lit comme suit:)) coil (flexible metallic hose assembly). (a)
Français:
couronne n f (a)
normalisé par un organisme national ou international
Forme habituelle de conditionnement des tuyaux métalliques flexibles enroulés sur eux-mêmes. (a)
Note(s): ((Titre de la source citée:)) Tuyauterie - Tuyaux métalliques flexibles - Vocabulaire des termes généraux.
((Dans la source citée, l'entrée se lit comme suit:)) couronne (tuyauterie métallique flexible). (a)
RBT3285152

Domaine(s)
métallurgie
tube métallique
Anglais
coil (bc)
Français:
Note(s): Tubbing copper seamless ((...)) 66 ft coil. (c)
couronne n f (ab)
Note(s): ((Dans la source citée, l'entrée se lit comme suit:)) couronne ( de fil). (b)[Office de la langue française, 1990]

While "suction" does look like the most likely candidate, in terms of overallmeaning of "aspiration," a Google search for "suction coil" yields only some very exotic examples. From Termium, for "aspiration," relating to plumbing/heating:

English:Compressors
Refrigerating Machines and Appliances

low side s CORRECT

low pressure side s CORRECT
suction side s CORRECT
low pressure s TRANSL. SOURCE
DEF - that part of a refrigerating system operating at approximately the evaporator pressure. s
DEF - Low-pressure side of the system extending from the refrigerant control through the evaporator to the inlet valve of the compress

The other possibility would be "vacuum coil" -- Termium does have an entry for "aspiration" rendered as "vacuum." Here is what I find with Google:

[PDF] www.marlocoil.com/steamcoil_o&m.pdf
... 8 1.0 PRODUCT DESCRIPTION The Marlo steam heating coil is a steam to air ... 1/2" - 15 degree swing check valve vacuum Coil should be supported at a minimum ...

www.geiselheating.com/geiselonline.com/support/Carrier 38 T...
... wish blower to function only while the heating or cleaner user's manual for proper ... The to clean the exterior surface. Vacuum coil surface using an up and ...

for others in the area of heating/refrigeration, see: http://ww.google.com/search?q="vacuum coil" heating&hl=en&lr...
http://www.google.com/search?q="vacuum coil" refrigeration&h...