Received-SPF: pass
 receiver=logan.com; client-ip=24.25.9.102; envelope-from=eanderson@carolina.rr.com
Message-ID: <000a01c629fc$74d82ea0$2402a8c0@edward2>
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-970506@logan.com>
Subject: Re: [FlyRotary] Re: NPG Coolant Temperature vs 50/50
Date: Sat, 4 Feb 2006 21:32:48 -0500
MIME-Version: 1.0
Content-Type: text/plain;
	format=flowed;
	charset="iso-8859-1";
	reply-type=response
Content-Transfer-Encoding: 7bit

 Hi Chad,

Good suggestion.  I have no idea whether Subarus may have a cavitation 
problem at higher rpms.  I think the rotary takes over 7500 rpm to get into 
that problem region. I've never had that problem {:>).  However, if a 
cavitation problem existed which reduced the flow rate of the 50/50 mixture 
and then they filled up with the higher viscosity NPG, then that  would tend 
to eliminate/reduce the cavitation due to its higher viscosity as you 
suggested.
Then we would end up with a higher effective flow rate for the NPG and that 
would indeed lower the delta T required because of the large Mass flow. 
Certainly sounds like a plausible possibility.  I still have a tiny bit of a 
problem because as I recall even at lower rpms/ground run-ups for example, 
folks have reported lower temps with NPG - seems unlikely caviation would be 
present then.  But, cavitation reduction could certainly be part of a the 
answer.

Ed

----- Original Message ----- 
From: "Chad Robinson" <crj@lucubration.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Saturday, February 04, 2006 9:05 PM
Subject: [FlyRotary] Re: NPG Coolant Temperature vs 50/50


> Ed Anderson wrote:
>> 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.
>
> I don't have the answer, but how about a hypothesis? Suppose they have a 
> cavitation problem. A more viscous fluid tends to reduce the onset of 
> cavitation, no? And is there any data on what pressure their system is 
> being run at?
>
> Regards,
> Chad
>
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:   http://mail.lancaironline.net/lists/flyrotary/
>