heat exchanger plans...

[Ronmar]

Bob
On my 6/1:

Exhaust port.  1.47" dia
Flange ID.  1.74" dia
Peppercan inlet pipe ID. 1.68" dia
Peppercan inlet pipe OD. 1.88" dia

But by far the most restrictive part of this exhaust system are the twenty .275" outlet holes on the peppercan.  These 20 holes have a total area of 1.19 SQ/IN.  As a comparison, the 1.47" diameter exhaust port has an area of 1.69 SQ/IN.  1.19 SQ/IN equates to a 1.23" ID pipe...

[veggie]

Jens,

I agree with all your points. I wanted to see just how hot the gases can get that far from the head.
It suggests that your insulation is doing a very good job.
Something we all need to be aware of as we progress with Bob's exchanger ideas.

Thanks for doing that,
Veggie

[mobile_bob]

for the exchanger to operate at  its optimum, it needs to be mounted as close to the head as possible, the pipe feeding it
ideally will be insulated, so that the maximum heat can be delivered to the exchanger at the highest velocity consistant with
that of the exhaust port.

Ron:
thanks for the specific's, that info provides all i need to know to work out the sizing requirements.

those twenty holes equating to less than the area of the exhaust port likely is still larger than the area of the port
at the valve/seat at full valve opening.

back to crunching numbers here.

thanks guys

bob g

[oliver90owner]

Bob,

I can understand your need for temperature but diameter seems a bit superfluous?   The important things appear to be gas volume per unit time and available temperature drop.  Your exchanger can modify the exhaust gas speed by simply having a reducer or increaser(?) before the actual exchanger?

Regards, RAB

[mobile_bob]

RAB:

i have a different design philosophy, which mirrors conventional "pulse" maniflold design
in that you do everything you can to keep the exhaust gas velocities as high as possible
without adding (appreciably) to back pressure.

by increasing diameters one increases surface area, which in turn allows for moreheat to escape
than would be the case with smaller amounts of surface area. you also set up standing waves that reverse
back up the pipe with each step in diameter in the exhaust runner, if i don't have steps and keep a consistant
runner diameter with that of the port it is one variable or set of variables i don't have to contend with in my
opinion.

i want the highest available heat, at the highest veloctiy to enter into my exchanger, for reasons that
will become apparent once you see the design.

my thinking is that there is 6hp in the exhaust of a 6/1 (running at peak load) and i don't want any degradation
of that power if i can help it, i want all 6hp presented directly into the exchanger. the closer i can get to this ideal
condition the more efficient the exchanger is at getting the hp converted to btu input to the water, and the better
able the unit is in ability to keep itself clean.

there is also cylinder scavenging, which is generally always desirable, and particularly so where we have something downstream
that might ordinarily present back pressure. while the effect might very well be slight, it appears to be enough so to offset any
pumping losses associated with the use of the exchanger.

that was one of my concerns in early testing, it is all good to harvest heat so long as there was not a penalty in fuel economy
that made it more costly than need be. as it turns out there is actually a slight improvement in fuel economy using my exchanger
on my changfa 195 over that of the oem muffler, and the unit turns out to be a better muffler than the oem to boot. this might be
explained by the obvious standing wave and reversion provided by the oem muffler making scavenging not as complete (which is
theory i realize, but until someone can find another explanation it seems as plausible as any for now).

my changfa port size is right at 1-5/8" so i chose schedule 40 black pipe that was 1-1/2 because it measures out to be right at
1-5/8". i port matched my flange and the pipe has one 45 degree elbow that is a nice smooth bend,  the end result is a system that
works very well, so i am hesitant to continue to work the design by introducing other variables that might cause unforseen issues
that might be hard to sort out later.  if that makes sense?

i just want to continue the project building on what works, produce the plans for distribution, and later should someone that has a set of plans decides he knows better and makes alterations for whatever reason, well... he can either be the beneficiary of the improvment or suffer with something may not work as well as it should. my responsibility is to try to make it so that if someone buys as set of plans and assembles an exchanger by following the directions he will be able to get the same results i have.

ymmv

bob g

[bschwartz]

I'm all excited to see the results!  Do you have an ETA for release of plans, and a approximate MSRP?

[Ronmar]

for the exchanger to operate at  its optimum, it needs to be mounted as close to the head as possible, the pipe feeding it
ideally will be insulated, so that the maximum heat can be delivered to the exchanger at the highest velocity consistant with
that of the exhaust port.

Ron:
thanks for the specific's, that info provides all i need to know to work out the sizing requirements.

those twenty holes equating to less than the area of the exhaust port likely is still larger than the area of the port
at the valve/seat at full valve opening.

back to crunching numbers here.

thanks guys

bob g

Yep, those were the numbers, along with bore and stroke, that I was also interested in when I was crunching these same numbers. 

Yes, you are probably right about the peppercan hole area being larger than the  actual exhaust valve exit area. 

IMO, probably the most important area in design of an exhaust exchanger, is to have adequate volume in the first chamber to completely absorb all of the cylinder volume, sent there over the course of 1/4 of a cycle(exhaust stroke).  After that you have the remaining 3/4's of the cycle to allow the exhaust gas to pass into the remainder of the heat exchanger.   In my planning, I was aiming to have at least the same passage area, if not more than the existing exhaust port and peppercan exit area. 

[mobile_bob]

Ron:

the prototype worked out to well in excess of displacement, looking back i could have done with approx 3x displacement, maybe.

but yes that was one of several factors that went into the design.

bob g