heat exchanger plans...

[mobile_bob]

Jens:

thanks for the added info, if my back gives me a break tonight i plan on crunching some numbers and get a start
on a working formula that i can use to do some projections, then maybe this weekend i can test the projections against
actual measured results to see if the formula works.

i think the bandwidth is sufficiently large so that the exchanger can operate over a fairly wide range and still be within
the flat part of the efficiency curve.

much easier to build to a broad operating curve than one that is "peaky" in my opinion, especially since folks will want to operate
over a fairly broad output range from their engine.

this was not something i originally did much testing on, because i don't plan on running my unit at anything other than 90-100%
capacity, save for warmup after startup and cool down before shutdown.

bob g

[veggie]

BTWE Bob, I took some more temperature measurements and it looks like we are closer to 300C but it's really tough to know exactly what is going on because I get different readings all over the place. The latest readings have me thinking that maybe cylinder #1 is not carrying it's fair share of the load. That is especially strange since #1 has always run slightly warmer than #2 and no modifications/changes were done to the fuel rack. The only thing different between #1 and #2 is that #1 has the high pressure fuel line heated.

Jens

Jens,

Seeing as you're taking heat readings....
Can I talk you into taking a reading 4 ft. from the exhaust port. How hot is the pipe ?

Thanks in advance,
Veggie

[veggie]

According to the "American journal of thermodynamics and food groups" Apples and Corn Flakes can in fact be compared.
I look forward to your readings. (on the metal.....not the insulation    )

Veggie

[mobile_bob]

Jens:

on your twin, does the oem mufflers screw into the head? or are there flanges that bolt on to the head
that the pepper pots screw into?

in any case, can you measure the id of one of the pepper pots on the threaded end?

from that i can determine the design port velocity from the head, this much i must know to size the exchanger
properly.

then if anyone else knows what the id of a pepper pot at the theaded end for a 6/1 that also would be useful


i don't need the id measurement down to .001" but within a 1/16" or about a mm,  would be close enough.
but if i can get more accurate measurement  i would sure use it.

got some work done tonight on a sizing formula, and a chart made up to input some test data to see if i can get
a relative correlation between test results and predictions from the formula.

i think the relationship between the internal spec's are related to port velocity and cylinder displacement factored against rpm
and the fuel consumption rate per hour.

what it appears as now is there is a compromise wherein one might give up some full load efficiency to operate at max efficiency at low loading, basically to get maximum efficiency at 1kwatt for a 6/1 i would expect to take a hit in effiency at full 3kwatt output.

the question is how much of a hit in efficiency?  that i don't know, however

your 20/2 running between 5 and 9 kwatts, with an average of 7.5 appears to be a much easier to calculate and build a unit that is centered at ~7.5 kwatt, so that the efficiency might be off a bit at both 5kwatt and a bit less at 9 kwatt. i feel very confident in its ability
to operate well in that application. i think you would have good heat operating from ~60-90% loading capacity, rather
than the 6/1 running from ~33-90+%.

that spread looks like it might be a problem for the 6/1 application, does anyone know how hot the exhaust is at the about an inch out from the port running at 1 kwatt loading?  if it is down much below 300 degree's F, i don't think any exchanger should be used in that range, you get to where you overcool and loading up the exchanger is the likely result.

not saying it couldn't be done, but would be much easier to work with between about 2 kwatt and 3.x kwatt output on a 6/1
basically i would have to be very careful in sizing for a 6/1 running at a consistant 1 kwatt load, and in that case it would probably be
a good idea to build another prototype for that specific application and put it into beta testing with someone running long hours.

i think i know of a board member that runs lots of hours with a 6/1, perhaps i should build one for that application and get it to him for testing. it would be something i would feel better about doing before a plan release for the 6/1,

just about all other applications i feel much better about and don't think it necessary to got to as much trouble to size properly

bob g

[JohnF]

Bob;

I would need a range - for a 6/1, a 10/1 and a S195.....

John.

[AdeV]

then if anyone else knows what the id of a pepper pot at the theaded end for a 6/1 that also would be useful


i don't need the id measurement down to .001" but within a 1/16" or about a mm,  would be close enough.
but if i can get more accurate measurement  i would sure use it.

Bob - the ID of a pepperpot for a 6/1 is a gnats cock over 2" (2.050" to be exact - but that extra 0.050" may be wear in mine).

[rl71459]

so... a gnats cock is .050"?

[AdeV]

On average 

[Ian]

I believe the standard Lister and Listeroid exhaust flange is threaded 1.5 inch BSP.

Regards,
Ian

[mobile_bob]

so is BSP approx 2.050 od, and about 1.5" id?

that would make sense to me.

bob g

[Jedon]

"Although a few species are up to 1/2-inch long, adults commonly are about 1/16 to 1/8-inch long"

So .050 would be almost as large as it's whole body, that's a studly gnat!

[AdeV]

so is BSP approx 2.050 od, and about 1.5" id?

that would make sense to me.

bob g

Not on my setup it ain't....

I measured 2.050 ID on a pepperpot exhaust; the threads are on the outside of that. I've locked the workshop up now & it's too cold & late to go back in there & measure the OD. I can do that tomorrow.

Do you need the ID of the flange bit as well? Or instead of? I'd say that was less than 2"; probably the 1.5" that Ian quoted.

[mobile_bob]

i suppose what would be of most use would be the most restrictive area in the system,
1.5 inches seems more appropriate for a 6hp engine than a 2" id

even 1.5" is really too large for a 6/1 in my opinion, but that ok, if thats the way it is.

thanks guys

bob g

[veggie]

so is BSP approx 2.050 od, and about 1.5" id?

that would make sense to me.

bob g

Bob, FYI ... I screwed a 1-1/2" NPT nipple directly into the threads of my exhaust flange. (Model 6/1)

Veggie

[veggie]

Jens,

Wow! 480 degrees f  ....Much higher than I thought it would be.

Veggie