REFLECTOR: Need for Cabin Heat at Altitude

Mon Jul 1 12:10:09 CDT 2013

Brian,
Just a small reverse scoop forward of the aft firewall should suck cool air from the nose compartment down the duct and out.  No forward scoop at all. 

Sent from Rene's iPad. A pleasure.  Go Apple.

On Jun 30, 2013, at 10:45 PM, Brian Michalk <michalk at awpi.com> wrote:

> Thanks for the information.
> 
> By the way, I am currently separating my oil lines, as suggested by Scott, I believe.
> I flew on Saturday in 104F heat.  CHT's were manageable, but the oil temp was not.  This was the first test after capping off my second parallel oil cooler.  Results were better than previous.
> If the split oil lines do not get me the cooling I need, then I'll probably install the fan and reconnect the second oil cooler.  If that still fails, then I will try ventilating my ducts to turn them into coolers too.
> 
> If I can get this to work in 105F weather, I will be able to fly anywhere.  Density altitude at my 600' airport was 3500'.  Incredible.
> 
> On 06/30/2013 05:07 PM, Ruben Creus wrote:
>> It took approximately 10min..  Note that the oil temp is read at the engine block, so assume that cooling the cooler only cools a small amount if oil at a time and then heats when running back into the engine… so the cooling effect needs a bit of time to really cool down the oil as a whole.
>>  
>> When reached 195F I left it there for another 10 min and it did not change, but you could see the temp going back and forth to 194 – 195.
>>  
>> When I did this same test in the winter with a temporary set up, the OAT was 15C instead of 35C, and I was able to get the oil go down to 185F. So ground cooling PASS!!  I will report this next winter about the heat in the air, but as I said, I just tried it in the air this week and it was blowing a very decent amount if air in the cabin, and definitely very hot… I had to turn it off as I was cooking myself there. So I have high hopes, but until the real test happens all is a hypothesis, a very good one though….
>>  
>> About the fan, yes it was the Jabsco 105CFM.   They have more powerful models but I could not find a place to fit it. Also from reading about heat comments last year,  it looks like the speed of the air going through the radiator is a factor, the slower the hotter it gets. So, more CFM might give you more air but less hot….So I figure it our that if the 105CFM give enough air then the slower the better. I guess in a perfect world. There will be different point of speed/temp with different models… but we do not live in a perfect world!
>>  
>> Ruben
>>  
>> From: Brian Michalk [mailto:michalk at awpi.com] 
>> Sent: Friday, June 28, 2013 10:27 AM
>> To: Velocity Aircraft Owners and Builders list
>> Subject: Re: REFLECTOR: Need for Cabin Heat at Altitude
>>  
>> Okay, that does look just like the Jabsco blower that we found.
>> 
>> How long did it take to bring your oil temps down to 195F, and did you stop taking data at that point, or did it stabilize there?
>> 
>> 
>> 
>> On 6/28/2013 8:05 AM, Ruben Creus wrote:
>>> I sent this message was it was not posted, so here goes again… see if this time works.
>>>  
>>> Here I attach some pics. As you can see the flap opens and closes that naca scoop. As the fan is pointing at a 90 degree angle in relation to the oil cooler you need to create a perfect seal, so the naca scoop becomes a chamber where air gets pressurized and the only escape is the oil cooler.
>>>  
>>> In my tests I noticed that if the chamber is not a perfect seal, then and air escapes, if the air escapes then there is I no pressure built up, and therefore no air going to the cooler, but when the chamber is sealed then all the air builds up and can only go to the cooler. The other test I did was with a normal blower fan, and it losses a lot of CFMs vs. de squirrel cage fan that loses very little CFM. You can see that on the fan                   manufactures specs. Someone wrote a nice message explaining the difference and the reason for this. What I found out that the propeller design does not move much air when it has pressure in front of it, but with the squirrel cage each blade pushes air to the next and so forth… I am not fan engineer, but in practical terms it was a huge and extremely noticeable difference. I guess that is why they use squirrel cage fan for all ducting systems (like A/C) use squirrel fan, and open air systems use normal fan propellers.
>>>  
>>> I did a test yesterday. OAT was 35C (95F).  I started the engine and the oil go up to 215F, then close the flap and turn the fan on and oil temp when down to 195F, allowing me to stay in the ground for as much time we want. (very convenient in large airports).
>>>  
>>> The other tests was in flight to close the flap and open the fan, and I had a very decent amount of air going to the cabin, pretty hot air!!  So very promising. Now I just need to wait until the winter to give a final verdict, but the amount of air is very decent and the temperature was very hot. So we will see what happens in the winter months.….
>>>  
>>> I hope this is helpful and not too boring.
>>>  
>>> Ruben
>>>  
>>>  
>>> 
>>> 
>>> 
>>> 
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>>  
>> 
>> 
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