Can anyone advise me of the required (optimum) thermal rejection rate
(BTUs)
for a Mazda 13B rotary oil cooler for an aircraft installation?
Regards
Craig Spence
Cobra Aviation - Australia
The oil is one third of the total cooling requirements. You can determine
that from this WOT heat balance chart for a 13B. For example; assume
the basic engine is 200 HP net representing 28% of the total heat in a
gallon
of gas. Total theoretical heat in the fuel would then .28 x Total Heat = 200
HP
Total Heat in the fuel is therefore 200 /.28 or 714 HP.
>From the chart the oil cooling is about 8% of that so .08 times 714 HP
is 57 HP. One HP is equal to 2545 BTU's per hour. Oil cooling is therefore
145,065 BTU's per hour.
BTW turbo compounding is a hot topic lately so 45% of the 714 HP
or 321 HP goes out the exhaust in the form of waste heat.
Paul Lamar
Craig Spence wrote:
Thank you Paul. I should rephrase my question to the following:
We are considering a 25,000 BTU oil cooler for a 13B for installation for
supplementary cooling. Would this be sufficient? Most oil coolers that our
cowling can accommodate are in the 15,000 to 45,000 BTU range. We are
maximizing water-cooling with two radiators.
After a long period of R&D, we have developed our own PSRU, inlet manifold,
exhaust system, engine base plate, redundant ECUs, engine mount and many
other modifications. We are very pleased with the performance.
Regards
Craig Spence
Craig Spence wrote:
25,000 or 45,000 BTU's per hour will not work. You need 145,000 BTU's per
hour if my arithmetic is correct. You need to redesign your cowl.
Another thing to consider is any oil cooler used with a Mazda engine should
be tested to well over 300 psi. The company that makes OEM Mazda oil coolers namely
Modine claim 300 psi. http://www.modine.com/english/index.php
What are the core sizes of the radiators you are using? A total of 600 to 750
cubic inches are required. Preferably no more than 2.5 inches thick.
Paul Lamar
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