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Heat Muff Orentation

pa38112

pa38112

Well Known Member
I was just sitting at the table playing with the new heat muff that arrived today from Vans. I bout a second to put in series. I never thought too much about the orientation of the excentric mounts. I have always placed the inlet/outlet ports on the high side. I'm starting to think that they should be on the low side. - Does anyone have data to support the delta T one way or another?
 
The flow velocity is high enough that I don't think port orientation matters.
What does matter is pipe temp and time exposure to the hot pipe(s).

The best performance comes from having the muff(s) on the hottest portion of the pipes possible.
There is also performance gain from ganging two muffs together in series.
 
Heat muffs in series

rvbuilder2002 said:
The flow velocity is high enough that I don't think port orientation matters.
What does matter is pipe temp and time exposure to the hot pipe(s).

The best performance comes from having the muff(s) on the hottest portion of the pipes possible.
There is also performance gain from ganging two muffs together in series.
Click to expand...

I would love to see photos of two heat muffs in series. Anyone?
 
I'll have one by the end of the weekend, but I always forget how to post photos on there. I'm doing one per pipe. I have not figured out the scat runs yet.
 
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Not in series, but one muff off cyl 1, and the other off cyl 4. The airflow is in series, combined they work almost too well.
 
dwrichey said:


Not in series, but one muff off cyl 1, and the other off cyl 4. The airflow is in series, combined they work almost too well.[/QUOTE]

Seriesed airflow is what I meant. It doesn't matter if it crosses over to the other side of the engine. Just so all the flow passes through two heat muffs.
Click to expand...
 
wirejock said:
I would love to see photos of two heat muffs in series. Anyone?
Click to expand...

Hi Larry,
I have an M1B in my 7A. Heat was anemic with single muff on #1 ex pipe. I had Rick Robbins make a short muff of my design to go on #4. Additionally, since I was blocking the majority of my oil cooler anyway, I picked up the input air from the back of the cooler. So, the flow is: cooler, #4 muff, #1 muff then cabin.

All this did make an improvement however like Scott said, pipe temp (egt) makes a big difference. I can't run low RPM over square LOP in the coldest winter days and expect the heater to keep me warm. Push some flame into the exhaust with RPM or ROP and the heater will keep up when it's COLD.

Sorry for no pics. Expercraft.....

RIGHT. Made it home to real 'puter. Here is a link to my older VAF post on same subject with images until they disappear due to Expercraft. Look quick.

http://www.vansairforce.com/community/showpost.php?p=862678&postcount=6
 
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Sorry no pics but I run 2 muffs in series on my O360 powered 7 with the Vans supplied Vetterman exhaust. The muffs are both installed reverse flow (discharge out closest to the prop) and hooked up in series (discharge of one flows into the inlet on the other) to a single heat box. I now get much more heat in the cabin than with the single muff. Barely warm with the single muff at -6C last winter. This winter at -10C (coldest so far) and very comfortable under full overcast. FWIW.

Al
 
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Agree with Scott, two in series is the way to go, at least for the RV8. I did that on my first RV8 with a Vetterman crossover exhaust and I had plenty of heat in the winter. On my new RV8 I have an AWI four into one exhaust and just one heat muff - and its not enough, so I?ll be trying to figure out how to add a second muff in series with the other one, although there are some space constraints in my installation. With two heat muffs in series, it shouldn?t be a problem.
 
I just posted some photos on my blog today (see signature below) - a couple of shots showing the heat muffs connected "in series".
 
pa38112 said:
I was just sitting at the table playing with the new heat muff that arrived today from Vans. I bout a second to put in series. I never thought too much about the orientation of the excentric mounts. I have always placed the inlet/outlet ports on the high side. I'm starting to think that they should be on the low side. - Does anyone have data to support the delta T one way or another?
Click to expand...
Pa38112, I think you're asking a good question. If you ask a chemical or mechanical engineer, they'll tell you that for optimum heat exchange you should always have the gas (air) flow opposite of each other. Since the exhaust flow direction is fixed that means if you want to get maximum heat exchange you'll need to have the inlet on the low side and outlet on top.

I live in northern Vermont and the Van's supplied heat muff was a bit weak at high altitudes in January - to say it politely. I think I've found a fine solution to my mediocre heater in January problem. I've just purchased from Aircraft Spruce the following:

https://www.aircraftspruce.com/catalog/eppages/turboheat05-15249.php

The muff is built of thicker aluminum than the one supplied by Van's. Also it contains Al rods wrapped with Cu wire. which creates turbulence inside the muff and more effectively transfers heat from the exhaust pipe to the cabin air. If you look at the photos on the Spruce site, see the tubes Cu windings. You'll also see a removable restrictor that is used to control the air flow rate. I l left my restrictor at maximum flow and I use just a bit of stainless steel scrubber to control the flow by placing it between the Al rods inside. Controlling flow rate is also critical to optimum heat exchange so don't ignore constricting air flow out of the muff if you need maximum efficiency from the muff.

All of this might too much for most aircraft but in Vermont you need to maximize heat exchange. I've included a photo of my set up. After I finish my annual and the next snow storm passes I'll let you know how well my setup works.

Elm
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ElmBrook said:
Controlling flow rate is also critical to optimum heat exchange so don't ignore constricting air flow out of the muff if you need maximum efficiency from the muff.
Click to expand...

Constricting output flow is quite important, so for sure dont disregard this easy to do item.

As far as the coiled copper of the AS muff, you can do the same thing but more direct transfer with some stripped household 14ga wire (or if you have stainless steel TIG rod, that works good too). Coil it around your favorite screw driver shank (or something similar) so its like a spring and then wrap that spring around the exhaust pipe. Clamp your heat muff over the whole thing......Just make sure that your coils are large enough to engage the airflow as much as possible, but not squished by the walls of the muff - no need to transfer heat to the muff walls....
 
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