I think while there
are lot of Nifty looking gadgets out there, you need to keep in mind that what
may work well for a piston engine in cooling oil may not for the rotary.
The basic reason is the rotary dumps approx 1/3 of its total waste heat load
(not counting exhaust heat) through the oil. In fact, you can calculate
the approx BTU you must get rid of through the
oil.
A 13B turning 6500
rpm with an 12.65 (best power) air fuel ratio will be flowing approx 16.1
gallons per hour. This equates to needing to get rid of approx
2650 BTU/MIN of waste heat through the oil cooler. Now using
the old heat transfer equation Q = BTU, M = mass flow and
Dt = temp difference,
cp (air = 0.25)
Q =
M*Dt*cp and
assuming you heat up the air so that it exits 100 deg F hotter than it went
into the cooler, then solving for the air mass M required = Q/
Dt*cp = 2650
/100*0.25 = 106 lbms/min or 106 pounds of air per
minute.
A cubic foot of air
at sea level = approx 0.0765 lb/cubic foot. So to get 106 lbms/min you
need to have 106/0.0765
= 1385 CFM of air
flow through the oil cooler. Now that is a sizeable amount of air
required just for the oil cooler at a modest power output of 160 HP.
My point, is that,
before you go spending your money and adding weight and complexity to your
installation, sit down and determine what each element will do for you and
whether it is really worth the money and weight.
My person opinion is
that it is hard to beat the efficiency of a well position oil cooler with
adequate airflow through it.
But, just my
opinion. Certainly there are cases where a small cooling assist
might make the difference and these things might make the difference. In
some cases, space precludes the idea solution and in that case oil/water heat
exchangers and other methods are called for.
But, if you are in
the planning stages, my suggestion is strive to get the right sized oil cooler
positioned with good air flow.
Ed
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of william singer
Sent: Friday, December 18, 2009 4:51
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Radiator/Oil
Cooler Combo
Modine makes such coolers.
My Ford Thunderbirds (89 to95) have them. wiliam
singer
----- Original Message -----
Sent: Friday,
December 18, 2009 10:26 AM
Subject:
[FlyRotary] Re: Radiator/Oil Cooler Combo
Our 1992 Honda
Accord EX Wagon has a oil to water heat exchanger that is sandwiched between
the oil filter and the engine block. It is about 2” thick, the same
diameter as the filter, and mounts with a longer hollow stud than would be
used to mount the filter directly to the block. I have no idea of its
capacity.
Steve
Boese
-----Original
Message-----
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Thomas Mann
Sent: Friday, December 18, 2009 9:03
AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Radiator/Oil
Cooler Combo
….does anyone
know of an oil filter mount that includes a heat
exchanger?
T
Mann
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