Best Heat Muff Intake?

[avrojockey]

Currently have mine connected to inlet ramp in front of #2 cylinder. Wondering if I should switch to right-rear baffle behind #3 cylinder like other installations.

Sans other variables, what provides the best combination of flow/heat?

 

[KayS]

lately i opened a thread with a similar question. no sufficient airflow from heat muff connected to baffle ramp and i wonder if air intake from rear baffle is the better option.

seems avrojockey has a similar problem. inputs would be very appreciated.

 

[Marc Bourget]

The emphirical approach would employ a manometer to determine the relative "Delta P"

That said, SCAT tubing has a large internal drag component.

 

[JDeanda]

My Exerience

RV-6, O-320. Cabin heat muff inlet is on the aft, right, vertical baffle, thru a screen and into a 2” SCAT hose, the to an Aircraft Spruce Turbo Heat muff. (https://www.aircraftspruce.com/catalog/eppages/turboheat05-15249.php?clickkey=80990). I have far more flow than I can even use or even modulate easily, but very very little heat. I taped off most of the inlet, which did nearly nothing. I’ll pack the muff with steel wool next but even that did very little on the old muff. I’m in southern California so cabin heat has not been a priority but now that we’re entering an unusually cold winter I may end up adding a second muff, plumbed in series to the existing one.

 

[Vfr1200]

Dual

Planning on dual heat boxes with dual heat muffs , does anyone have pictures or builders blog of dual install ? I have the vetterman exhaust and one of his heat muffs , looking at the turbo heat muff ACS sells .

 

[blaplante]

I put seat heaters in my 6. Between the stock heater and those... all's good and nice, at least down to freezing. Haven't flown in anything colder. Cabin insulation would be my next priority. That sidewall by my knee sucks out heat.

 

[rvbuilder2002]

RV-6, O-320. Cabin heat muff inlet is on the aft, right, vertical baffle, thru a screen and into a 2” SCAT hose, the to an Aircraft Spruce Turbo Heat muff. (https://www.aircraftspruce.com/catalog/eppages/turboheat05-15249.php?clickkey=80990). I have far more flow than I can even use or even modulate easily, but very very little heat. I taped off most of the inlet, which did nearly nothing. I’ll pack the muff with steel wool next but even that did very little on the old muff. I’m in southern California so cabin heat has not been a priority but now that we’re entering an unusually cold winter I may end up adding a second muff, plumbed in series to the existing one.

Do not use steel wool.
Use stainless steel pot scrubber pads (looks like a ball of stainless steel ribbon).
Expand the ball so it has some open space within its volume to allow air to pass through.

 

[b727capt]

Here is how I did it on my RV7

 

[wawrzynskivp]

best place

From my understanding the best spot is where you achieve the highest stagnation. For me that seemed like the rear baffle was the best spot. I am happy with the flow achieved.

 

[Malndi]

Currently have mine connected to inlet ramp in front of #2 cylinder. Wondering if I should switch to right-rear baffle behind #3 cylinder like other installations.

Sans other variables, what provides the best combination of flow/heat?

I recently made this change (from in front of #1) and the result was a significant loss of cabin heat. I’m considering changing it back.

In my original configuration the scat tube was running from the inlet ramp through the space above the exhaust and inlet tubes before going into the heat muff. Now wondering if this was providing some pre-heating in the tube that the more direct route doesn’t.

 

[lr172]

I recently made this change (from in front of #1) and the result was a significant loss of cabin heat. I’m considering changing it back.

In my original configuration the scat tube was running from the inlet ramp through the space above the exhaust and inlet tubes before going into the heat muff. Now wondering if this was providing some pre-heating in the tube that the more direct route doesn’t.

Thanks for sharing. The plans for the 10 have the heat inlet on the #2 inlet ramp and I put mine behind the #5 cyl. I have often wondered why I don't get the very high heat output that other 10 owners discuss. I had assumed the pressure/velocity would be similar and clearly that was wrong.

Larry

 

[KayS]

From my understanding the best spot is where you achieve the highest stagnation. For me that seemed like the rear baffle was the best spot. I am happy with the flow achieved.

could you explain the thinking behind highest stagnation in more detail?

i now branch off the right forward inlet ramp with insufficient airflow and like to try the rear baffle. probem is that i closed the hole in the rear baffle during firewall forward and now it would be major surgery to swap to the rear just for testing.

 

[wawrzynskivp]

could you explain the thinking behind highest stagnation in more detail?

i now branch off the right forward inlet ramp with insufficient airflow and like to try the rear baffle. probem is that i closed the hole in the rear baffle during firewall forward and now it would be major surgery to swap to the rear just for testing.

If we buy into Bernoulli's idea, then the faster the air is moving the lower the static pressure. As your air goes into the cooling plenum it is going to transition from TAS velocity to something less. The only place where you will maximize the static pressure would be where it stagnates to its slowest velocity.

Lot's of good work and info on this subject by the venerable Dan Horton. With or without thinking about it we will either build a cooling system that attempts to keep velocity high and pressure low just inside the cowl opening, or one that tends to cause the beginning of stagnation just before the air enters the opening. Van's seems to be more of the former so one might find higher static pressure available further inside the plenum space. (By plenum I just mean the air above the engine with a properly built set of baffles) So what we are doing is establishing higher pressure above the engine than we find at near free stream velocity at the cowling exit. Air then flows from high pressure to lower pressure and we get our cooling. As a side note, you can cut the stock Van's exit down quite a bit and maintain really good engine cooling flow if you work on that transition and reduce all the unintended stagnation at the stock exit. (See Vetterman's work on the stock exit shape to see just how badly the air slows down) Keep the velocities high at the exit and it'll really pull the air through your engine. I reduced my exit area by about 60%. Of course your challenge is to compare pressure at the heater ducting inlet and cockpit pressure.

The higher the static pressure between the entrance to your heater ducting and your cockpit outlet the more flow you should be able to obtain.

The consideration of providing unfettered access to higher velocity air in your exit air path has implications for the cockpit heater as well. Did you do anything to reduce cabin pressure? I have a sizable port on my baggage wall to take advantage of the lower pressure in the tail come area.

Of course that's all academic. Sometimes the application finds a better answer than the theory.