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Date: Sat, 4 Feb 2006 19:48:20 -0700
From: Bob White <rlwhite@comcast.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] NPG Coolant Temperature vs 50/50
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Hi Ed,

You need to look at a 13% increase in delta T.  If Delta T is in the
range of 20 to 50 deg., the increase is only 2.6 to 6.5 deg.  I don't
remember report of lesser temperature, but the increase wouldn't be
that great. 

Bob W.


On Sat, 4 Feb 2006 20:56:49 -0500
"Ed Anderson" <eanderson@carolina.rr.com> wrote:

> Hi Al,
> 
> Appreciate your (anybody else welcome also) views on one other thing that is still bothering me about the use of NPG.  
> 
> Given that NPG+ has a specific heat of 0.66 at 212F or  20% less than  the 0.82 for the 50/50 mixture and given that NPG+ is  approx 7% more dense than the 50/50 - then that for the same flowrate for both it would seem that NPG still has a 13% lesser overall capacity for heat transfer  (at the same temps 212F and flow rates).
> 
> Also assume that the engine is produce the same heat load (Q),lets take alook at what temperature we might see with NPG+ compared to the 50/50 solution.  We have from the oldie but goody Q = c*M*DeltaT the ability to solve for the temperature increase, DeltaT.
> 
> Delta T = Q/cM, now if the combined effects of c and m  provide 13% less heat transfer capability than the 50/50 mixture that would indicated that to carry away the same Q at the same flow rate, the delta T of NPG+ would need to increase by 13%.  So if I were getting 180F with the 50/50 for the same Q load (and flow rate) then with NPG+,  I would expect 180 *1.13 = 203F.  Yet, if I understood correct we have reports  that lesser temperatures results noted by users of NPG - this leaves me a bit puzzled.
> 
> If my assumption is correct thus far, then I am at a loss to understand the reports of lesser cooling temps when using NPG+, it would seem just the opposite would happen, that is - the coolant  temperature would increase. 
> 
> Now,  If the coolant temp with NPG+ actually does  remain  the same (or decreased) for the same Q and flow rate,  then it could indicate the engine heat load is not being carried away as well as with the 50/50.  IF the reports of lesser cooling temps occurs when switching to NPG+  are correct, then it would appear to me that the engine must then be operating under a higher heat load (i.e heat not being transfer to the radiators as effectively) .  This doesn't even take into consideration the possibly lesser flow rate of NPG+ for the same pump speed as the 50/50 due to its higher 3 times higher viscosity (at 212F). 
> 
>  Yes, I have no problem understanding that boil-over has been eliminated - but, is NPG actually cooling as well as coolant temps may lead one to believe? I mean with NPG, I could have a excessive block temperature and still not have boil-over - but my rotary engine would likely have suffered damage.
> 
>  What am I missing? Inquiring minds (even old ones) want to know {:>)
> 
> Ed A
>    


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