Heat Exchanger pot for melting snow

Optimus Weekender HE works pretty good and is reasonably priced. But it is only a .9L pot.

Thanks. I read the thread about Optimus Weekender HE and FMS XK6 1L Pot.

Does anyone actually use these for melting snow? I suppose melting snow in smaller pots like these is a real problem. Also one would prefer the pot to be wide as a narrow pot with fins is really prone to generating CO.

One of several threads on Jetboil Hacks

I have a Snow Peak Gigapower under a Sol and it works great.

Here is a photo by Todd Harper –

I also use a modified jetboil pot for melting snow which has yielded great results. I went the way of dremeling a few slots in the jetboil pots base to allow my stoves to sit up inside the base of the pot closer to the HE fins.

Nice. The Jetboil mod is interesting. My question is how does the limited capacity work out for you guys? Is the convenience of larger / wider pot (say 1.5L) worth the extra weight for melting snow?

you can melt snow in smaller pot – when it gets half full of water, pour half it into container and then put more snow in…

a little more fiddling than with a bigger pot

Huzefa:

I've got two Primus Eta 1.8 liter pots. I weighed everything three times because it wasn't adding up until I figured out that one pot was lighter than the other pot and one lid was lighter than the other lid.

Pot, no lid: 258 or 265 grams

Lid: 98 or 103.

Total weight range: 356 to 367 grams. I can't see any visible sign why the weights are different. Maybe they changed the specs, the coating thickness, or maybe they got in slightly different sheet metal stock. Maybe bring your scale to the store?

I like the Eta a lot. I like the non-stick coating. I like the lid – the little handle is light, folds flat but stays up when you want it and it works nicely. The lid has enough of a lip to sit securely on the pot. The pot is sturdy, not floppy, it's only shortcoming is there is no integral handle. So you need a separate pot gripper – a not very ultralight one off the rack is 45 grams. I've made my own out of aluminum flashing and a popsicle stick at 14 grams. Or use your bandana, but then you probably don't fill it 85% full. I also like that at 1.8 liters, you have a decent amount of "freeboard". It would hold 2.05 to 2.1 liters filled to the brim, which would be unusable. I really like the ring that protects the HX fins. That protection ring also allows me to use on a wide variety of different stoves without the pot supports getting stuck or cockeyed on the HX fins. And I really like that the HX fins are 1 inch "wide" (ID to OD). Jetboil's bigger pot has only 1/2" wide fins and no fin protection ring. The ID of the fins is only 3.8" so you want a smaller flame pattern than for some HX pots. The OD of the bottom of the pot is 6.3", the top OD is 7.4". I have been known to use the Eta in the kitchen when I'm rushing to get water boiling for pasta or sterilizing canning jars*. HX fins while BPing save fuel. HX fins at home save time. (of course, they do both in both settings).

The other large snow-melting pot I have (I do live in Alaska), is a Jetboil 3 liter. The 3 liter mark is a good 2 cm below the rim. To the rim it would hole 3.5 liters (again, that would be an unusable amount in there). The non-stick coating is okay, but the Eta's seems more substantial. It has integral pot handles (a loop on one end and two fold-out handles on the other end, coated in orange plastic. I guess the fins don't extract as much heat as they hoped (or I pack a bigger stove), because I've scorched the plastic coating on the handles. The pot is wider (8.3" OD) and the HX fin circle is wider, too at 5.5" ID – both of which are better for efficiency. Weights for the 3-liter Jetboil:

Pot only: 373 grams.
plastic bottom protector: 82 grams
top plastic lid: 77 grams.
Total pot+ lid+bottom protector: 532 grams

I'd MUCH rather have a welded metal fins protector ring a la Primus than a plastic cover (which does nothing for you in use). The fins sit oddly on my stove pot supports unless your pot supports are within 5.5" OD (in which case, they fit inside the HX fins). The plastic lid isn't as easy to use as a nice metal lid (like the Primus). It's a touch lighter, but you could go with aluminum foil and save a lot more weight. I don't like how the plastic lid needs to pried on and off – it seems like burned fingers, or spilled pasta waiting to happen. Most often, I flip the plastic lid upside down so I don't have to pry it on and off. That reduces the usable pot volume a bit, but condensation drips at least drip INTO the pot instead of over the sides.

Chemical Engineering note: For snow melting into cold water, the lid doesn't help you much. The top of the water has snow on it most of the time so it is at 0C/32F with very little loss of water vapor (and heat). It is as you approach boiling that heat loss off the water surface gets more significant. If half your water is drunk cold and half goes into hot drinks and meals, then >80% of your fuel use is during times of cold to warm water temps. Only 10-15% of the burn time would be with hot water in the pot and that's when you want to have a lid. Also, something no one thinks about – "an unwatched pot boils over". (Since we never bring glass lids with us) using a lid typically means overshooting the boiling point. And certainly you overshoot the simmering point which is all you need to sanitize water, make hot drinks, or rehydrate pasta. So sometimes I save fuel but NOT bringing a lid. When I see bubbles start to form and moderate amounts of steam coming off the water, I shut down the stove. 80 grams less lid and 80 grams more fuel would melt and boil several more liters of snow. And lids you carry in AND out. Fuel you only carry in.

*my most obscure use of HX pots: prior to producing dry ice fog for 9 performances of Peter Pan, I'd boil 10 gallons of water and transport it to the theater in ice chests. Boiling all that water happened faster with my three bigger HX pots on the stove.

Would adding an MSR heat exchanger to a Primus ETA Power cook pot increase the efficiency enough to validate the extra 5.6oz?

>"Would adding an MSR heat exchanger to a Primus ETA Power cook pot increase the efficiency enough to validate the extra 5.6oz?"

Only on a very long trip. Since the first, welded HX already extracted some of the otherwise wasted heat from the flame and exhaust, there is less left to be recovered by the last-gen MSR HX.

That said, an additional ring of fins or a welded-on vertical HX a la the MSR strap-on, would only add an ounce or two AND be more effective. I wish someone would offer a "double HX" pot (for lack of a better term).

David,
Where could I source extra fins that I assume I could aluminum braze on the pot?
Regards,
Paul

Hi David

> Total pot+ lid+bottom protector: 532 grams
My Ti pot (1.5 L?), with Ti lid, in bag : 174 g
Difference : 358 g

I use a bit less than 30 g of fuel per day. If the HE pot reduces that to 20 g, then that's a weight saving in fuel of 10 g /day. So I would have to be carrying more than 36 days worth of fuel to break even. Now, 36 days is going to take over 1000 g of fuel for me, or about 2.4 of the 450 g canisters. Am I going to try to carry 36 days of food and fuel without resupply?

If we are talking about use in snow country where all the water comes from melting snow, my fuel consumption changes to maybe 60 g/day – at the most. So that's 18 days of food and fuel. Am I going to carry all that without resupply? And where does one find snow country where you can go for 18 days without finding any free water? (Apart from the Antarctic…)

Seems to me that one has to work rather hard to justify the extra weight of a large HE pot? Or am I missing something else?

Cheers

"And where does one find snow country where you can go for 18 days without finding any free water?"

You might get pretty close to that on Mount McKinley, Alaska.

Or, if you were sitting up at Everest Base Camp for 18 days.

–B.G.–

"And where does one find snow country where you can go for 18 days without finding any free water?"

Many climbing expeditions face just this scenario. In particular, Alaska, Asia (Himalayas, Karakorum, ect) Andes, probably the Caucuses but I am not sure about that. Winter trips in parts of the US, and of course polar expeditions. lol

I still have one of the MSR heat exchangers, but never use it. It never 'penciled' out. In my tests it is a bit more efficient, and it speeds up snow melting a bit, but never enough to justify it's weight.

Years ago I had a stainless evernew (I think it was an evernew) pot that had an aluminum outer that directed the heat along the pot. It actually worked well. I have always thought that an all AL or a Ti/Al version might actually be worth it for climbing trips and winter where one is melting snow for your water.

Roger, you're comparing a 3-liter HX pot to a 1.5-liter non-HX pot. So much of the difference is in the pot size. Then there is the greater strength (in the examples I own) of the HX pots than the very thin-wall pots ULers gravitate towards. So the payback, apples-to-apples is much sooner.

When I add fins to a soda can and compare it to a soda can without fins, the payback on the fins is in very few people-days. Likewise if I add vortex generators on identical SS pots.

30g a day of fuel, I calculate as boiling about 3 pints of water. Which sounds right, maybe even generous, in summer, if you're trying to be UL and using all the tricks you clearly know. But in winter, per person, I'd probably have a pint of hot drink am another pint pm, plus a cup for oatmeal in the am and a pint to cook dinner so at least 3 pints nearly boiled, therefore 3+ pints melted. And at least two more quarts melted to drink as cold water during the day (cold air is dry air). So more like 100-120 grams fuel per person per winter day without a HX. And while I'll go UL in the summer, and especially on a high-mileage, solo trip, I don't cut it so close in the winter, with kids along, nor with my wife. Remind me in one, maybe two months, when there's snow right outside the door, to run a HX / non-HX side-by-side comparison.

I wish someone would market really light HX pots. It would make these really light, low-output alky stoves much more viable. And let you do more with your canister stove.

"And where does one find snow country where you can go for 18 days without finding any free water?"

We don't go out for 18 days, but we take the kids snow-camping in February and March when the ice on the lakes and streams can be 4 feet thick. So maybe 12-16 people-days. HX fins weigh much less than a drill, auger with extensions and a hand pump (but I have brought those once or twice).

Paul: I've folded my own at home. I posted about 2.5 years ago on a jig I made up to make wavy sinusoidal folds from flat strips of aluminum. I used JB-Weld, which worked okay. Someone posted about an even higher-temp epoxy(?) but I couldn't find a supplier. Do you have a way to braze it on? That would be sweet.

David, someone? Who could that have been?

http://www.miller-stephenson.com/epoxy/

I've been using some high-temp epoxy from this company for decades.

–B.G.–

No, I'd remember if it was you, Bob. It was someone who gave a source of adhesives for brake-shoe manufacturers. Miller-Stephenson look like that have a lot of offerings. What is the temp rating on the product you use?

When you start looking at heat exchangers on a pot, you find that they just increase the "heatable" surface area of a pot. So, looking at a JetBoil pot, you just keep in mind a picture of a wide bottomed pot. Both types of pots (wide bottomed or a JetBoil w/HE) perform similarly.

I did many experiments many years ago with simple grease pots. The bottom was annealed, then ridged with a simple jig making from 3-9 grooves in the bottom. Each groove was about 1/4" deep. This gave me a pot with about 18% more surface area on the bottom.

This translated really close to heating efficiency increases at about 17% in the lab (not quite a direct relation.)

The downside was cleaning the pot. 9 grooves was too many to get my finger in to clean out food bits. 7 rings was much easier to clean but only yielded a 15% increase in fuel efficiency.

Roger's calculation is unfortunate. Whatever numbers you want to use, it's hard to make up for increased weight of hx pot with fuel savings.

If you can decrease fuel usage so that only one canister is required rather than two, then you save several ounces of the metal canister.

Surface area of fins is good, but another factor is directing all the hot exhaust to next to the pot. Like that cone shaped wind screen. Have the smallest gap between windscreen and pot without hurting combustion.

"What is the temp rating on the product you use?"

It beats the crap out of me.

When I first got it 35 years ago, it had some high-temp rating, enough to withstand wave soldering with room to spare. Now the tubes are so old that I can't find the item listed in the catalog. Still works.

–B.G.–

> Roger, you're comparing a 3-liter HX pot to a 1.5-liter non-HX pot.
This is true, but do you really need a 3 L pot?

For a start, I can get the same throughput by bailing water out as the snow melts and dropping more lumps of snow in. Yes, more work, but then I am just sitting there in comfort inside my tent.

Of greater concern to me is that large 3 L pots have been indicted in several cases of stove 'problems'. The very wide pot reflects too much heat back down onto the stove (and canister, if an upright). That makes me a bit nervous.

Winter – it may be that my experiences have been too limited. Up high I may not be able to find free water for a day or two, but I can usually find it on the approaches. But, maybe that's Australia. To be sure, Everest or polar regions … but our average reader might not go there.

Cheers

"To be sure, Everest or polar regions … but our average reader might not go there."

I've been accused of lots of things, but I have never been accused of being average.

I didn't see any running water for several days getting up to Everest Base Camp, twice. I didn't see any running water on an expedition high in the Andes.

I didn't see any running water on the Hawaiian volcanoes. But then, there was no snow to melt, either.

For lots of places where we ski in California, liquid water can be found, but it gets pretty risky trying to retrieve it. Melting pristine snow is much better.

–B.G.–

But if you calculated the average percentage of days the average bpl person has to melt snow, it's probably 5% or less

I've done it a couple times, but it was just for the sake of doing it, but I'm not into snow camping all that much