Does a lid reduce fuel use and how to tell if water is pasturized

[Jerry Adams]

for that testing, it was at 2000 feet, water started at about 40F.  Like I said, the data was normalized to 150 F increase in temperature of the water, and 450 g of water.

yes, Jerry likes Freakonomics.  I like the one where they showed that child car seats aren’t effective.  The administration official they asked for comments said he doesn’t comment about people that cherry pick data to support their outlandish claim.

which takes me to the one (Freakonomics?) about the Oedipus Trap.  He didn’t think that woman was his mother so he carried on.  Then, when he got data that contradicted his belief, he was so invested in his decision to marry this woman that he couldn’t conceive it was actually his mother.

Like I have so much invested in the belief that lids work so find it difficult to conceive that maybe they don’t : )

[jscott]

 

Actually, once Oedipus understood that his wife was his mother, he blinded himself. Not the same thing as carrying on as before. He was blind to his offence, and when saw, he put out his eyes as an act of repentance–or, as Freud ‘saw’, an act of self castration. the incest taboo is general throughout all societies world wide, going back into ancient societies.

“yes, Jerry likes Freakonomics.  I like the one where they showed that child car seats aren’t effective.  The administration official they asked for comments said he doesn’t comment about people that cherry pick data to support their outlandish claim.”

Well, Freakonomics has an agenda too: they’ve gotta blow our minds several times a week detailing how what we think we know is false. Like the administration official, I’ve wondered what the show wasn’t telling us in their reports in order to achieve that goal. In a related context, I remember a spate of books claiming that good mothering practices made no difference in a child’s development, since genetics determine everything. A child raised with a mannequin stand in mother in a closed room with no windows will turn out identical to one raised in a loving environment and access to nature and friends, these accredited geneticists claimed.  Very Freakonomics, very scientific and very wrong.  Still, I enjoy the episodes, even when they fail to convince me.

I suppose I DO have something invested in using a lid on a pot: long habit and lessons learned from mu mother in the dim past. maybe it DOES feel threatening to who I am and my mother’s memory to boil without a lid…outdoors, in cold temps…with winds blowing…

Nah.

[W I S N E R !]

Well, mothers are really great and all but it appears that boiling with a lid on isn’t that amazing. A difference of 406 seconds versus 346 seconds, according to this science fair project.

6:47 versus 5:46 is hardly going to derail my dinner plans. But I guess if Archie Bunker is screaming “Where’s my pasta Edith?!” a minute could feel like a really long time.

[Jerry Adams]

oh good, another data point, 406 vs 346

that would be like 6 g of fuel to boil with lid on, 7 g of fuel with lid off.  A little more than the gear skeptic measured, or I did, but it depends on factors like how high you turn the burner up.  Maybe geometry of pot and how much water matter.

It was econtalk – https://www.econtalk.org/megan-mcardle-on-the-oedipus-trap/#audio-highlights

Oedipus trap is a term coined by Megan McArdle.

“Yesterday I wrote about what I’ve called an Oedipus Trap: a situation where it would be so psychologically devastating to discover that you’d made a mistake–even completely innocently–that you will do everything in your power to avoid recognizing it.”

I think Oedipus, after marrying the woman, started getting clues she was his mother but denied for a while until it became impossible to deny, then he ripped his eyes out.

Econtalk is a libertarian podcast.  Often interesting.

[David Thomas]

David D: Even if wind and temperature at elevation have been controlled for, the flame is going to be richer at elevation.  Richer flames are cooler due to with CO production and unburned fuel and therefore waste fuel compared to a burner tuned to the air density.

[David D]

Dave, background to my question: BPLs PRD tests averaged 5.6oz cups boiled/oz fuel with no wind at 68F for ~ 2 cup boils.  I consistently get 10 cups/oz fuel from my PRD in same conditions, MSR claims 9 cups/oz, and for similar stoves and conditions here 7.5, here 9, here 8.5.  Using the BPL numbers at face value would lead to moving up to a heavier cannister on a week long trip

I thought the effect might be elevation, and agree for a stove without a pressure regulator: too rich a fuel/air mixture.

A pressure regulator adjusts for the air density to get a proper fuel air mixture back.   The test I quoted from BPL was for a PRD with regulator, so my guess is that the BPL tests set the flame high for fast boils at the cost of efficiency.

[Roger Caffin]

A pressure regulator adjusts [URL to MSR] for the air density to get a proper fuel air mixture back.
The MSR reference makes a good story. But frankly, I don’t believe all of it. Some of it, yes, but only a little bit.

However, to my mind the whole MSR spin on pressure regulators is an attempt to sell upright stoves into places where you should be using an inverted canister stove. Butane boils at ~0 C, so if you are trying to make coffee at -10 C you can always expect trouble with an upright. The pressure regulator will have no effect on how the gas in the canister vaporises: you will get the 30% of propane boiling off and be left with the 70% of butane sitting there at -10 C (or most likely lower), not vaporising at all. Then where are you?
I should add that I have previously vented on this subject:
https://backpackinglight.com/pressure_regulators_myth_part1/

Well, my 2c.
Cheers

[DAN-Y]

However, to my mind the whole MSR spin on pressure regulators is an attempt to sell upright stoves into places where you should be using an inverted canister stove………………….

I should add that I have previously vented on this subject:
https://backpackinglight.com/pressure_regulators_myth_part1/

Well, my 2c.
Cheers

 

 

I agree……— End of free preview —  ;)

.

[Jerry Adams]

I think pressure regulators have some value

they don’t allow you to operate at any lower temperature than a regular needle valve

but, if you’re at low temperature, with a needle valve, the temperature of the canister drops as you’re using it, so it will slow down.  When I notice it I’ll turn the needle valve some more to get it running faster.  Slightly annoying.  With pressure regulator it will just run.

also, the MSR and SOTO versions are both pretty good regardless of whether it’s a pressure regulator valve.  I’ve used both for years without problem.

[DAN-Y]

95% of the people don’t know diddly squat about stoves….they are ones that benefit from the pressure regulators. They are the ones that NEED it.

 

but, if you’re at low temperature, with a needle valve, the temperature of the canister drops as you’re using it, so it will slow down.  When I notice it I’ll turn the needle valve some more to get it running faster.  Slightly annoying.  With pressure regulator it will just run.

 

 

Faster….speed it up…..we wantFASTER.

[Jerry Adams]

good point, we don’t need to be fast.  It’s less efficient…

but a pattern I’ve repeated many times is that when I put a pot of water on for coffee, after a few minutes of puttering around, the stove will slow down to almost nothing.  Then it will suddenly hit me that the reason this is taking so long is that it’s cooled down from evaporative cooling so I turn it up.

I like it taking 4 or 5 minutes, but when it takes 10 minutes, that exceeds my patience

I don’t like the sensation of suddenly realizing the stove has slowed down.

this is not a big deal.  Not enough of a reason to get rid of your needle valve stove.  But, the SOTO and MSR regulator stoves are nice stoves and the regulator is a slight advantage.

just my opinion : )

[DAN-Y]

Moulder Strips have been used sucessfully to prevent the slowing down.  It’s all about remembering what we have learned in the past.

Regulators have their place.— End of free preview —

 

[David D]

Roger, did you ever do a part 2?

I’ve watched a new interview with an MSR rep this week on the topic of stoves.

Their claim for the pressure regulator benefit is it allows the stove to purposefully designed for low pressure.   He didn’t go further, but it implies less fiddling as pressure changes.

To my mind, based on a fairly thorough knowledge of carburation, flame temperature should also be examined.  If this more consistently allows an optimal fuel/air mixture, it could increase efficiency.  But that would be seen in better boil times, which don’t seem to be shown

[Jon Fong / Flat Cat Gear]

Here is an article from MSR on pressure regulators. Some of the basic physics are fine, the graphs are misleading. What a properly designed pressure regulator will do is clip the maximum pressure to a set value. In the case of this stove, it depends upon what the valve is set to. Say, the internal pressure of a canister is 45 psi. If you dial the valve into a high setting, it will be lower than the canister level. Say that max setting is set to 15 psi. As long as the canister pressure is above 15 psi then the output will remain the same (input, 15psi-45 psi / output 15 psi). When the canister pressure drops below 15 psi, then the output will match the canister pressure. With a pressure regulator, you will not get any more gas out of a canister.
Since the output pressure is regulated, the orifice size can be optimized to the 0 psi to 15 psi range (instead of 0-45). What the regulator can do is limit the dynamic range of burner output. Basically, it would prevent a new user from just turning a stove on full blast (at 45 psi) and wasting a lot of gas. Experienced users just turn the flame level down on unregulated stoves.  My 2 cents.

https://www.msrgear.com/blog/technology-stove-pressure-regulators-work/

 

[Roger Caffin]

Hi David
Yes, there was a Part2 , but I can’t find it now. Possibly lost when the BPL web site was replaced. All my old URLs are no longer valid. I will keep searching.

Their claim for the pressure regulator benefit is it allows the stove to purposefully designed for low pressure.
Sort of marginally true, but imho quite irrelevant to our needs. SOTO came out with one, so (my opinion) MSR had to copy. It’s a marketing thing.

Why is it irrelevant? For at least two reasons. The first one is simple: any careful user will be there monitoring his stove and adjusting it as needed. It is (again, imho), far too dangerous to set a stove running and then to walk away. Anything could happen.

The second and bigger reason is technical. The biggest pressure drop is not across the jet but across the needle valve, conventional or complex. You just don’t need to optimise the jet for 0 – 15 psi (which is still a very big range, and 0 – 45 is not much different). Proof of this statement is to be found in the tens of thousands of small upright non-regulated stoves sold every year. Sold, and happily used by the customers. They work fine.

<Technical exposition>
What a stove needs is a fast jet of gas coming out of the jet dragging air in through the adjacent air-holes. How much gas comes out is set by the user via the needle valve. Far more important for a good flame than size-of-jet is the amount of air dragged in, and that is controlled by the position of the jet with respect to the air-holes, and the size of the air-holes. Mind you, I have seen a 2:1 range in size of air holes, so the size can’t be too critical. I have done a fair bit of experimenting with this to see what was going on inside the burner column.

The typical jet has a 0.30 mm diameter hole. (The drill bits are a bit fragile at that size.) I have tried diameters from 0.27 mm to 0.33 mm and found that the conventional needle valve can handle that. To be sure, if you go down to 0.20 mm you have worse than halved the flow, so the stove is going to be rather feeble. (Technical footnote: owing to friction between the gas and the edge of the hole, such a drop in diameter is far worse than you might think.) (Second technical footnote: this helps to explain why dirt in the jet has such a serious effect.) (Third footnote: 0.20 mm drill bits are very fragile! And expensive!)

If you go from 0.30 mm to 0.40 mm you have to significantly increase the flow of gas to get enough velocity to drag enough air in – and you might need bigger air holes as well. But then you will have a furnace and may be melting the bottom of your pot.

So the size of the jet has little to do with the incoming pressure; what matters is the velocity of the gas flow coming out that is important. The amount of gas coming out is controlled by the needle valve. Again, proof is found in the number of stoves on the market with simple needle valves.

Sorry for the long-winded reply. The fine details of the physics fascinates me, but is probably of little interest to anyone else than a good stove designer. Sadly, imho, not all stoves have had a good designer.

Cheers

[David D]

Yup, familiar with MSR’s sites and the claims.  For me the convenience provided by the regulator is more than worth the few bucks.  It also helps make sure I don’t screw up and accidentally burn too much fuel finding myself having to cold soak (blech) at the end of a long trip.  Sure you can compensate for the risk by carrying a big cannister, but no thanks

>What the regulator can do is limit the dynamic range of burner output.

That’s what I meant about the potential of a regulator to improve efficiency.  Sort of like a carburetor having a primary jet, and needle jet optimizing turbulence for different flow rates, better able to achieve a complete burn and optimum fuel/air ratios.  The stove pressure valve is similar to a CV carb spring and diaphragm.  A CV is much better at not wasting gas and in achieving more even fuel mixtures under different conditions.  Now, a stove’s flow rates will be nowhere that of an engine turning 10krpm, so this benefit is not remotely as useful for a stove at such low gas velocities.  An indirect way to tell is by testing gas/burn and burn times, which I haven’t seen any compelling evidence favouring regulator stoves (so agreeing with the conclusions)

[Roger Caffin]

Hi David

I think the Part2 became the Addendum to Part1.

Cheers

[David D]

Thanks Roger.  I find this interesting as well.

If you’re interested, look into some of the underlying thermodynamics of carburation for vehicle engines, especially as written about by Kevin Cameron from Cycle World (very digestible, he’s a true master of his topics).

“If you go from 0.30 mm to 0.40 mm you have to significantly increase the flow of gas to get enough velocity to drag enough air in – and you might need bigger air holes as well. But then you will have a furnace and may be melting the bottom of your pot.”

I wonder if increasing the fuel without adequate air flow will cool the flame.  In internal combustion, enrichening past the Stoichiometric ratio decreases flame temperature as the unburned fuel has a cooling effect

[Roger Caffin]

Hi David

I wonder if increasing the fuel without adequate air flow will cool the flame.

Yes [edited MK]

There is no good reason to reduce the temperature of the flames [edited MK]. If one wants less power the stove can be turned down. In fact, there are very good (albeit indirect) reasons to keep the temperature as high as possible.

If one has not enough air in the mix the flame temperature will drop – but the flame goes orange and sooty. That soot is unburnt carbon from the fuel, which means that only part of the energy in the fuel is being used. That is not only wasteful, but it means one has to carry extra fuel.

If one has too much air in the mix [edited MK] the flame would be cooled, but again that reduces the efficiency of the stove in use. And, in my experience, it means the flame is a lot less stable. It can lift off the burner head and go out. Key phrase here is ‘flame lift off’.

[edited MK]

Cheers

[edited MK]

 

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