REFLECTOR: Oil Coolers

[Al Gietzen]

I don't understand the difference in pressure that one oil cooler would see 
versus two oil coolers in series???

Ronnie

I may not understand the question; but oil pumps are basically positive
displacement, so will pump a certain flow for a given rpm, regardless of the
pressure it's pushing against (ignoring the pressure relief bypass in the
engine).  So if one cooler has a 20 psi drop across it, then two in series
will have 40 psi drop (plus some fitting losses), so the first cooler in
series now sees 20 psi higher pressure.  With cold oil the pressure drops
could be high.

However; I think every engine, certainly the aircraft engines, has an
internal bypass relief valve downstream from the pump which will bypass the
coolers if the back pressure is too high.  Whether the cooler is subject to
damage depends on the design pressure of the cooler, and the adjustment of
the bypass pressure.

Al