REFLECTOR: Need for Cabin Heat at Altitude

[Ruben Creus]

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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