Sterno Inferno model 70138 High-tech Sterno?

[Gary Dunckel]

This morning I wanted to check Dan’s assertion that water would boil faster without a cozy than with one. Using a crappy alcohol stove with the Inferno pot/pot stand, heating 2 C of 48* F water with .75 fl oz of alcohol, the water in the pot WITH cozy boiled at 9 min 45 sec, and without a cozy it boiled at 9 min 15 sec. So the water did indeed boil a bit quicker when NOT using a cozy, 5.1% to 5.4% faster, depending on the point of reference. Although this is a sample size of just one test of each, I tend to think that maybe Dan was right. I had previously reported my findings of the cooling rate of the boiled water, and that the cozy reduced the cooling speed by 25%. All of these statements relate to an aluminum pot, and I would expect that a titanium pot might perform differently. The tests were done on a 70* F morning with no breeze at all. It will be interesting to see if there are similar results if a significant wind or stiff breeze is present, and also if the ambient temperature is somewhere near freezing.

At this point I see that the slow cooling of using a cozy somewhat compensates for the slightly quicker boil time. Trade-offs, huh?

[DAN-Y]

You’ll get better results when you use the Starlyte XL3 I sent out today ;-)

[Stormin]

Alpkit Brewpot windshield setup.
Initial boil test, Ambient air temp 26.8c.
Water temp 21.5c.
500ml of water boiled in 7min.04 sec.
Soot present.
Stormin Stove used.32 mm high x 52mm diam.
Stove height to pot bottom=50mm
Two rows of 20, 10 mm holes.
3 Rivets and spacers used to hold pot inside windshield, 5mm below top.
Windshield 73 mm high.
Brewpot 117 mm base diameter,135mm high with 4 incremental measures to 1 litre. Hard anodised aluminium.
Cozy used whilst boiling.
15 ml of bio ethanol used, Burned out at 8min.15sec.

[Gary Dunckel]

I hope so, Dan, and I expect that it will. Today I made a pot screen/support that is 3″ tall. Tomorrow I make the holes 1/2 way around the pot, to give me a “sans holes” side to place into the breeze/wind. Then maybe I can be one of the big boys with this project.

Good work, Stormin, and great results. Thanks for posting.

[DAN-Y]

Tony taught us by his (Schlieren photography) what heat looks like going up the side of a pot. Apply that to what we expect will happen if the pot is covered with an insulation material such as the cozy. Tony did the photography using the Starlyte Stove

[Stormin]

Dan,that affect cannot happen in this configuration.

[Matthew / BPL]

That photo is so cool.

[Dean F.]

Regarding cozy efficiency:  it’s also important to realize that the heat exchanger fins will work in reverse, too.  That is, once you remove the pot from the heat source they will speed cooling.  They’re a radiator.  You’d be better off without a pot cozy and just pouring off into a bowl with a cozy.  Glad bowls are light.

[Jon Fong / Flat Cat Gear]

“it’s also important to realize that the heat exchanger fins will work in reverse, too.”

Not quite true.  The heat exchange equation is dq/dt=hA(delta T): dq/dt=heat tranfer rate, h=convective heat transfer, A=area and delta T=temperature difference

h, the convective heat transfer rate is dependent on the air velocity and that is where the major difference will be.  While heating over a stove, it will be much higher than an ambient breeze.

Secondly, the temperature difference will also be quite different.  Several hundred degrees to say 212F while heating verses 212F to ambient off the stove.

It will cool down quicker with fins, nut probably not significant as instead of convection it will mainly be conduction cooling.

my 2 cents.

[Dean F.]

No- It’s absolutely true.  I mean, you say that what I posted isn’t quite true, but then provide the equations that show that it actually is true.  Huh?  It’s not as big an effect because nothing is actively blowing ambient air across the fins like the stove does with hot air, and also because the temperature differential between the air and the pot isn’t as great, but it’s true.  They will act as a radiator and cool the contents faster.  Which is what you said, but you just shouldn’t have said “Not quite true.”  “The cooling effect will be less than the heating effect from the stove” would be better.  And then we can goad the stove weenies here into testing just how much of a difference it makes.  :)  I would also point out that aluminum is fairly conductive, but that’s almost moot because I think you’re talking about heat transfer to the air.  Which actually will still convect.. but hell, we’re really getting off into the weeds, here.

And, Jesus!  I guess I should have known that BPL is the one place that I have to spell all of that out or someone with an engineering degree will try to tell me I’m wrong…  :)  I’m a scientist too, Dude.  Well… of a sorts…

It really doesn’t pay to try to be pithy, here, but I didn’t want to have to produce an f-ing dissertation…  :)

 

All probably reasons that I love this place, actually…

[Jon Fong / Flat Cat Gear]

Well, radiant heat transfer is a function of the difference in the fourth power of the absolute temperature difference.  212 F = 672 R and 70 F = 530 R so the absolute temperature differences are not that great.  Radiant heat transfer at these temperature are usually a minor factor.  my 2 cents

 

The bottom line is that it is unclear is fins on a mug (when used with an alcohol stove) is significant.  If I were looking at a gain, I would want a 20% improvement.  If you could routinely boil 2 cups of 70 F water using 12 ml of alcohol, I would be impressed.  Again, my 2 cents

[Dean F.]

Well- to now undermine my own argument- a lot of the radiant heat will also intersect another fin, which reduces efficiency, too.  The fins are pretty close together.  (IIRC an ideal radiator is a single gigantic 2-sided but infinitely thin sheet operating at as high a temperature as possible, or somesuch, so that multiple fins don’t radiate into one another.)  But direct conduction to air is not trivial since, after all, we aren’t discussing spacecraft, here.  Though granted the fins are mostly enclosed, and that helps, too.

But… weeds, again.  You can stop sucking me into physics discussions any time, now.  :)

I still want one of the stove weenies to test this for us.  :)

[DAN-Y]

Dan,that affect cannot happen in this configuration.

 

Sure it can. Heat will exit the exchange fins and go up the side of the pot that’s covered with the cozy. Cozy insulates the pot, therefore taking longer to heat the water.

The Inferno has no cozy so no concern.

[Stormin]

Dan, the heat escaping through the fins is minimal. I can hold the cozy/ pot combination with bare hands throughout the boil process. If the heat was that great it would melt the neoprene cozy.

 

 

[Gary Dunckel]

Well, Dean, I did report on my (1) test of speed of boil when using a cozy, vs. not using one. I also noted my findings of how fast the boiled water cools down over 30 minutes, when using a cozy and when not. It’s in the first post on this page.

The real side-by-side testing of the effect of using a cozy (vs. no cozy) will be done by Bob Moulder when he gets back from his eclipse chase. Wait for it…

 

[Dean F.]

Gary,

I’m not talking about the effects of the cozy.  I’m talking about how much of an effect the HX fins have on water cooling.  So I need you to rip the HX fins off of one of the pots and compare water cooling times with one that still has the fins.

Snap to it, stove weenie!

And I expect a rigorous footnoted report, with methods and visual aids, as well as quotes on water beginning and ending temperatures, salinity, and particulate load, ambient temperatures, and pot thermal mass, as well as the current phase of the moon.  Obviously.  One cannot neglect tidal heating.  This is, after all, BPL.

[Kevin Babione]

Dean – you left out measuring the effect of the solar eclipse on boil AND cooling times…

[Gary Dunckel]

Ah, I see, Dean. It’s not the cozy that you are interested in, but rather the HX fins. Having only one Sterno Inferno cup, I won’t be your man. We need someone that is willing to trash his/her Inferno pot, you know, for science. But there’s yet another consideration – the performance difference between the HX fins of the Inferno and those of an aluminum Jetboil Sol cup. As good luck would have it, the JB Sol fits perfectly on the pot stand/screen for the Inferno. My money would be on the JB for efficiency. The Sterno Inferno pot is a wee bit cheesy in the HX fin department.

[DAN-Y]

If you could routinely boil 2 cups of 70 F water using 12 ml of alcohol, I would be impressed.  Again, my 2 cents

 

Results of my 1st 3 tests(page 4) using alcohol and the fins =

11.3398 grams/ml

8.50486 grams/ml

8.50486 grams/ml

For what it’s worth!

 

[Roger Caffin]

Dan – quoting results to micro-grams seems a shade optimistic. Are you actually converting from ounces? Seems likely: 8.50486 = 0.3 oz.
Since a result of 0.3 oz is probably +- 0.05 oz, you should really be quoting 8.(5) g, with little confidence on the 0.5 g (0.018 oz) bit.

Cheers

[Jon Fong / Flat Cat Gear]

keep in mind that grams and ml are equivalent with water but not DA.  Please correct for the specific gravity.

[DAN-Y]

You engineers can figure it out

[Bob Moulder]

Klean Strip DA specific gravity is 0.798 and I have been calculating milliliters by dividing grams by specific gravity. I mentioned this upthread not too far and figured one of you professional scientists, engineers or mathematicians would’ve reamed me out by now if this were not the correct way to figure it.

A source of error I figured out today… if the cap is left off the XL-3 between burns, fuel continues to vaporize after the flame has been blown out. The result is that somewhere between 0.4 and 0.8g of DA was off-gassing between tests (as measured today), which means that the fuel consumption reported for previous tests was somewhat high because I used the previous ‘end’ weight as the ‘start’ weight for the next test. Now, I am simply weighing the stove right before and immediately after tests and the numbers are consistently lower. Now, if you ask me “Why don’t you just put the cap on?”… I have two answers for that; 1) the stove is still hot and might melt it and 2) fuel vaporizes on the inside of the cap, so there is still some fuel loss there as well.

OK, on to some more Sterno Inferno nerditations in the next post…    ;^)

[Bob Moulder]

Gary D and Dan Y have been very generous in helping me do some comparative tests to determine the possible advantages of a 3mm neoprene cozy. Gary sent me one of his custom-made Frogg wader cozies and Dan sent me a XL-3, Inferno pot and “Dinty” lid, and a sheet of stainless steel (SS) to make a pot stand identical to the Ti one I already made.

The first order of business was to make a pot stand from the SS. The SS sheet was about 1/8″ narrower than my Ti sheet, but I went ahead and made it almost to the spec of my Ti version and then did some tweaking to make them identical. Turns out that after I made the SS version I discovered I had punched 2 extra holes in it, so I punched 2 more in the Ti version to make them equal in that regard, and I trimmed 1/8″ off the height of the Ti version so that it was identical to the SS copy. Now they are as close to identical as I can get them.

I did 4 boils with each pot stand and consistently recorded fuel consumption of 10.2 (12.8ml) to 10.6g (13.3ml) per 2-cup burn with each unit, 58°F water temp, 61°F air temp. The SS version weighs 22.4g and the Ti weighs 12.4g after the little trim job. I don’t think the 1/8″ height difference or the 2 extra intake holes or the difference in materials made any significant difference — performance is still excellent. Now that the 2 setups are “normalized” I will be able to do the side-by-side cozy/no-cozy tests sometime in the next couple of weeks.

 

[DAN-Y]

I agree, performance is excellent. You get to have all the fun ;-) It will be interesting to see the test results of cozy-no cozy.

It’s used to snuff out flame and stays on burner while it cools down, prevents fuel loss by evaporation.

Here is the original XL compared to the smaller XL3 and Modified Starlyte on the left.

In my tests, I placed the silicone disc over the burner after blowing it out. Once the burner cooled the lid was put on and taken into the house to be weighed. The fuel that condensed on the underside of the disc was removed by sliding the disc off the burner’s top edge. Some remaining fuel may have seeped back into the burner. The small amount of fuel left on the surface of the burner was negligible but burned when I put the match to it.

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