Message

-----Original = Message-----
From: Rotary motors in = aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Russell Duffy
Sent: Thursday, January 06, 2005 2:21 = PM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: = fluidyne oil cooler

You should be able to get flow rate; pressure drop; heat rejection rating = from Fluidyne. Based on my calcs, it would be good to about a steady = 120 hp in a rotary, if you get good air flow through it.

How can you = calculate this without the info you mentioned? How much air flow is "good". What is the temp? I appreciate the = thought, but I don't really believe all the calculations in the world will give a real = answer when you consider all the variables. It might be interesting, and = will certainly be in the ballpark, but you won't really know how it works = until you try it.

I knew when I wrote it you = didn’t want to hear what I had to sayJ. And I didn’t say I was right, just based on my = calcs and comparisons, that was my judgement. I did the analysis for my installation, and just scaled your fluidyne cooler off of that. Of = course the answer you get depends on your objectives and assumptions. = I’d like to be able to run a continuous 75-80% power on a 90F day at climb = speed.

Yeah; a complete analysis is = complex, and beyond the tools that I have at my disposal. But back when I = was heading up an engineering analysis group, it was amazing what we = did. A few tens of thousands of dollars solved problems that hundreds of thousands = of build ‘em and bust ‘em dollars would never solve. I’m = just fortunate to still have some of the simpler analytic tools at my = disposal, so questions like “how much flow is good?” aren’t too tough and = gets you in the ballpark pretty quick. Take the amount of heat you have to = dump, the specific heat of the fluid, and an approximate temperature change, = and you can calculate the flow rate right now. Actually getting that flow = rate through the heat exchanger may be the tough part.

Fluidyne has tested their oil = cooler cores and have heat rejection heat rejection rates, pressure drops, as a function of flow rates, etc; it’s just tough to get them to give = you the data. I discussed it with one of their engineers years ago when I = was doing my design.

And you’re right; = ultimately you have to install it and test it. The simple analysis just increases = the odds of getting close on the first try.