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  #1  
Old 07-07-2018, 08:52 AM
BlackhawkSP's Avatar
BlackhawkSP BlackhawkSP is offline
 
Join Date: Jun 2011
Location: Indianapolis
Posts: 138
Default Heater bypass in summer?

RV-10 folks:

Has anyone here fabricated a duct to catch the heater bypass air and route it to the lower engine cowl exit, to save dumping it under the cowl? The purpose of this would be to lower the under cowl temps on these hot weather days.

Also, can bad things to happen to the exhaust system components if you simply block off the inlets to the pipe shrouds (the heat exchangers)? I'm looking to keep the firewall mounted EarthX battery as cool as possible in summer. I guess EarthX is about to come out with an insulated box too for help with this.
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Last edited by BlackhawkSP : 07-07-2018 at 08:55 AM.
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  #2  
Old 07-07-2018, 09:14 AM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
Posts: 1,022
Default Bypass

This was a mod I did on my -10.

The hot air coming off of the exhaust muffs goes to a "y" valve, which is controllable from the cabin. Normally, the hot air goes to the firewall heat valves, as in the vans plans. If I pull the bypass knob, the butterfly valve in the Y closes and the hot air is ducted out of the cowl.

You can see what I did in my kit log. Go to mykitlog.com. Search for Sunman, Indiana. Look at the Engine entry for 1-20-2018 for photos.

Not flying yet so can't say how it will work but in theory, should work fine...the good news is if it doesn't work, I can remove the valves and easily go back to stock.
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Aerospace Engineer '88

RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
Doors - Done
On Gear
290 HP Barrett Hung
ShowPlanes Cowl with Skybolts Fitted - Beautiful

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  #3  
Old 07-07-2018, 09:20 AM
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Carl Froehlich Carl Froehlich is offline
 
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Location: Dogwood Airpark (VA42)
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I used some of this between the cabin heat boxes and the firewall, then had it extend over the top of the boxes, then down the front of the boxes: http://www.aircraftspruce.com/catalo...clickkey=31128

The result is the hot cabin heat air, when the heat boxes are shut, bounces off the Koolmat then down toward the cowl exit, not right at the engine mounted fuel pump.

I also put a 3/4” restrictor on the back of the baffle 2” cabin heat SCAT hose flanges (a piece of aluminum with a 3/4” hole with some aluminum tape to hold it on the edge of the flange, the SCAT hose slides over it). This does two things:
- Less air to be heated so less hot air dumped into the bottom of the cowl. The RV-10 heat is way more than I’ll ever need. Even with these restrictors I have just the rear heat on part way on the coldest days.
- Less engine cooling air bypassing the engine, but still enough to keep the SCAT hose from getting too hot.

This setup has worked well - and I recommend it.

Carl
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  #4  
Old 07-07-2018, 11:37 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 3,008
Default

Quote:
Originally Posted by BlackhawkSP View Post
RV-10 folks:

Has anyone here fabricated a duct to catch the heater bypass air and route it to the lower engine cowl exit, to save dumping it under the cowl? The purpose of this would be to lower the under cowl temps on these hot weather days.

Also, can bad things to happen to the exhaust system components if you simply block off the inlets to the pipe shrouds (the heat exchangers)? I'm looking to keep the firewall mounted EarthX battery as cool as possible in summer. I guess EarthX is about to come out with an insulated box too for help with this.
Not sure why you would want to route the air to the cowl exit, as it will ultimately make it there on it's own without problems. I get reducing flow through the circuit to increase cooling efficiency for the engine (reducing wasted pressure), but don't see how directing the flow will help much, other than reducing heat load on the fuel pump that Carl mentioned.

I am curious to understand the reason, as maybe I missed something.

Larry
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Last edited by lr172 : 07-07-2018 at 11:40 AM.
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  #5  
Old 07-07-2018, 12:12 PM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
Posts: 1,022
Default heat

The way the -10 is set up, heat coming from the exhaust muffs is directed to the firewall heat valves. When these valves are closed, that air is deflected by the heat valve doors and that section of the firewall, back toward the nose gear. That air turns roughly 90 degrees and is always flowing...right against the .018 firewall. It is going to get hot.

We could also discuss the incremental reduction in △P by adding relatively high pressure air to the bottom section of the pressure cowl...

Dumping it in the cowl exit avoids both potential issues.

Though I am not airborne yet, I would tend to agree with reducing the inlet area for the SCAT tubing...
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Bob
Aerospace Engineer '88

RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
Doors - Done
On Gear
290 HP Barrett Hung
ShowPlanes Cowl with Skybolts Fitted - Beautiful

Dues Paid 2017,...Thanks DR+
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  #6  
Old 07-07-2018, 12:29 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 3,008
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Quote:
Originally Posted by rocketman1988 View Post
The way the -10 is set up, heat coming from the exhaust muffs is directed to the firewall heat valves. When these valves are closed, that air is deflected by the heat valve doors and that section of the firewall, back toward the nose gear. That air turns roughly 90 degrees and is always flowing...right against the .018 firewall. It is going to get hot.

We could also discuss the incremental reduction in △P by adding relatively high pressure air to the bottom section of the pressure cowl...

Dumping it in the cowl exit avoids both potential issues.

Though I am not airborne yet, I would tend to agree with reducing the inlet area for the SCAT tubing...
Thanks for explaining that. However, one must caution not to place the scat directly in the cowl exit, as that would reduce cowl exit area and therefore reduce the ultimate airflow through the cowl. I suspect the volume of air flowing through the scat is quite a bit less, relative to volume, than that lower cowl area due to all of restrictions in in it's circuit.

Larry
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  #7  
Old 07-07-2018, 04:46 PM
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Auburntsts Auburntsts is offline
 
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Location: Dumfries, VA
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Meh. Or you could just let it be. I fly throughout the Southeast year round and the heat muffs dumping hot air into the cowl isn’t an issue IMO. YNMV....
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  #8  
Old 07-09-2018, 08:24 AM
rcoleman-10 rcoleman-10 is offline
 
Join Date: Apr 2017
Location: Bastrop, TX
Posts: 9
Default Heater bypass in the summer

Heat management will always be a problem with the RV-10. My battery is in the tail cone so I don't have an issue there. With an EarthX in the FWF area heat management will be critical. I use two main products to reflect and control heat. I am seeing anywhere from 35% t0 85% reduction in heat pass-through. I wrap the oil cooler, the firewall, the fuel rails to each cylinder, the heater and oil scat tubes and many other items that you want to keep cool. When next at the hanger I will post some pix. I use ZircoFlex foil and Gold Foil from Thermal Control Products.

Phase II for the Gold Foil is inside the tunnel. Side walls, fuel lines, filter, pump...etc.

The foil is very light 5oz per sq yd so it does not add significant weight.

More to follow as I take measurements.

Ron
RV-10
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