I make coffee in thermos bottles. But I realized that they cannot be beat for general hot water. You wake up in the morning, boil up a gallon (whatever) of water and fill up your thermos bottles. You have near boiling hot water for most of the day.
Clark
Where’s the best place to buy big-size thermos type containers?
How about those ice/heat packs? Do they work? How long will they stay hot for? Will they heat water?
Such an amazing device, it keeps hot things hot, and cold things cold, but how does it know?
there’s some kind of barrier between the inside and outside that prevents the molecules from interactng with each other and thus allowing for transfer of motion.
(this would be my guess)
Thermal (heat) transfer occurs primarily through two mechanisms, conduction and radiation. By providing a vacuum layer, they interrupt any possibility of conduction. By silvering the inside of the flask, they provide a highly reflective surface, and therefore poorly radiative.
Since thermal conduction is a reciprocal process, it works either way…heat can’t get out or in, so hot stays hot, and cold stays cold.
Eccles – at 18:11 three ways -and radiation - that is why they are shiny. Just had to say that.
It was a joke!!
DennisC- Yes, Highly reflective means shiny. And I said radiation.
Please, don’t make me start bringing in black body and gray body emissivities.
You’ve been warned. You don’t know who you’re dealing with here.
conduction, convection and radiation that’s 3, I think I know- yes, you are the NASA guy. of course you don’t know who you are dealing with here :) the convection limited by little air between the walls , conduction by low thermal conductivity of stailess or glass, and radiation limited by the emissitivity in the IR range. (mostly centered around the 10 micron range).
But I must say, I enjoy most all your posts and respect your knowledge base. Something in me just snapped and I had to say 3. Forgive me.
conduction, convection and radiation that’s 3, I think I know- yes, you are the NASA guy. of course you don’t know who you are dealing with here :) the convection limited by little air between the walls , conduction by low thermal conductivity of stailess or glass, and radiation limited by the emissitivity in the IR range. (mostly centered around the 10 micron range).
But I must say, I enjoy most all your posts and respect your knowledge base. Something in me just snapped and I had to say 3. Forgive me.
DennisC- But convection is actually just a function of conduction. If we are looking to shed heat from the stored substance, we have denied heat a conduction path through the interposition of vacuum. Thus, the only mechanisms available for heat loss are solid body conduction at the mounting points of the inner vessel, and radiation. Convection would imply a fluid transport mechanism which does not exist in vacuum.
And I am not now, nor have I ever been an employee of Nasa. (Nor Nascar too, for that matter).
And don’t you realize, you are draggin me dangerously close to sounding like Duckie on NCIS?
sorry, I understand. They flush the really good thermos bottles with Argon so that even the remaining gasses are “slow” to transport the heat. I can see that some would call conduction and convections both kinetic transfer of energy by materials. I tend to think of convection as the something where the center of the mass moves with the transfered energy and conduction where the center of mass of the material remains about a fixed center. So to me a thermos seeks to reduces all three modes of thermal energy transfer. Sorry to ruffle your feathers. I can’t remember were I got the bogus NASA idea.
But all in all a thermos sure is nice to cook in. I use it for soup, rice, barley, tea, oatmeal, pasta, hot chocolate…… Since I live at high altitude (water boils around <94C here-yes that’s right- 80% atmosphere), it takes a long time if I cook “normal”. It just takes time here. Even with all this preping- I still opt for canned beans instead of the dried ones due to the time.
The narrow mouth ones are good since there is less loss (convection of steam to the smaller lid). I use those for cooking just a little. The large “pail type” are good for holding things for meals, taking food to a campsite, holding large volume for cleaning and so on. You loose a heat out the top, but they have a “larger thermal mass” and a lower surface to volume ratio so they stay warm for a good while.
I bought a large wide-mouthed one at Big Lots this afternoon for $4.99 — something like almost I think a gallon Igloo, and they had a smaller one for $3.99.
Oh yes, I also can “cook” in a thermos by using one of those submersion coffee cup heater (the coil that you hang in your cup and plug in). The one I have is just 50W and I can power it right off my inverter/solar array. It is amazing how easy it is to boil water in a thermos. Just get it to boiling, pull out the heater, and close the lid. (But note it can create a vacuum in the bottle as it cools and you need a screw type lid for your thermos).
I bought large-mouth thermoses (thermi?) because they seem as if they’d be easier to clean, and getting the starchy food out would be quicker. I’m not going to try them until I find bottle brushes to clean them. (We need an extra for the non-wheat eaters among us.)
I have cooked Angel Hair pasta very successfully in a wide-mouthed thermos. Also, the ones I have have screw-in plastic inserts that you can clean in the sink or dishwahser. it sure simplifies the clean-up after starchy foods.
Dennis- How long does it take to boil water with a (I assume) 12v 50W immersion heater? This would seem to provide alot of cooking off of a modest battery (Say like 11AH). Recharge with a 10W panel and you at least get some warm food every day.
Eccles at 19:29
I am using 50 W at 110AC of my inverter. It is just that my old “coffee heater” was a cheap 110 thing. I am not sure they sale them any more- Haven’t seen them around. It seems to take about 30 or 40 minutes to bring it to a boil. But for tea, I only need it “steaming hot” or about 60C.
(You might be able to “roll your own” from nichrome wire/sand resistors)
You can figure your energy need by m*c*delta T/effiecency. For me, I start with 10 C water (cold mountain stream source) and boil at 94 C (high altitude). So for 250 ml of water (about a cup) it takes 250 grams * 1 cal/gram* degree C * (94–10)degrees * (1/0.85)or 29 kcals. note-I loose about 15% of the heat due to vapor loss in an open thermos. or about 34 Watt hours (24.417….). For a 12VDC that is about 3 amp hours.
Of course, you could save a lot by starting with warm water. For most of my thermos cooking I use my Kelly Kettle and fire. But I love to have backups for everything and some times I may not feel like fire. It is so easy and I can do it in my “sick room” if needed.
By the way, those Kelly Kettles are great- Double “cylinder” with the fire on the inside to boil the water. - That means there is less little heat loss that is not directed through the water. It just takes a hand full of tinder. It takes the least fuel to boil than practical thing I have found.
Eccles - Oh, yes, In case there are others “listening in”, I would not use the plastic insert if you use a submersion heater.
You guys are great! I have such a big grin on my face!
The thermos are also good for making yogurt. Warm the milk to body temp- it doesn’t feel hot or cold when you touch it. Put into a thermos with a tablespoon of living yogurt (the good stuff you buy at the supermarket- make sure that the lactobacillus are alive). Stir. Put on the top and you have yogurt in a few hours.The longer you leave it the stronger (more tangy) it tastes. You can leave it in the thermos all day or over night if you like. See what suits you.
clark – at 20:19
That active culture yogurt is very good for treating diarrhea.
Here is another use for the bottle- If you leave water out (at least here) at night you can end up with cold/cool water in the morning- but it in the bottle so you can have cool water to bring down someone’s temperature if needed. I am lucky in that I have a COLD stream in front (5 to 10 C) so I can get and keep cool water for such things. Notice if TSHTF in the winter- don’t forget you might be able to freeze water outside in a pail and bring it in for the thermos for food storage if needed. (I haven’t tried that- I can “chop ice” from my pond in the winter).
Not meant to be humorous- The active culture yogurt may be good for diarrhea unless you are lactose intolerant, and then it may well just make matters worse.
Another thing the active yogurt cultures are good for is replenishing the beasties that live in your intestines after you have been taking antibiotics. I have found that yogurt culture helps keep things stable and reduces diarrhea caused by taking antibiotics.
Ladies, yogurt with live, active cultures is also good to prevent and cure yeast infections. Just google “yogurt yeast infections”.
My food thermos has three compartments so you can separate items. Plus it has the cutlery attached to the the thermos and a carrying strap. Tried it out and works great- three course meals yummy. I thought pricey $40. but now I think worth it.
Does anyone here understand the dynamics of solaroofs http://www.solarbubblebuild.com ?
Thought you’d be interested. :)
My trusty thermos (Alladin) was filled with steaming, hot coffee on the eve of Hurricane Andrew. Some hours later I was safe on the floor of the closet but my coffee was ice cold. Surely one of the thermos experts above can explain this to me. Barometric pressure or what? I have thought about this for years and could use the space in my head. The thermos never malfunctioned again and I wish I could say the same for my brain.
Lugon- it looks like what he is doing is using a double layer rof skin to create an air blanket for insulation. The bubbles create an entrapment structure such that air does not engage in convective heat transport. It is essentially the same idea as styeren foam or fiberglas insulation. SInce he is using a transparent skin, he looks like he intends to achieve solar gain, like in a green house.
Doc in Asheville- My guess would be that the intense low pressure of the arriving storm created a sufficiently large pressure gradient that the thermos unsealed itself and vented steam and gasses, thereby removing with it substantial heat. Once the pressure had bottomed and begun to rise again, the stopper resealed itself, and presented you with a sealed thermos, but obe which had been venting (and therefore cooling) for some time.
Solar energy, as in heating, and as a aircondition (!) is something everybody should take a look at. Having a passive solarheating system in the houses construction would be very usefull in a pandemic as well. And as the energy crisis is groving it would be a wise thing to consider for redusing energy costs. Solarheating is not the same as electric solarpanels. I recomned the book: http://tinyurl.com/qxaw2 I you own a house (i dont :( ) it is quite easy to create a hotair sirculating and heat storage system with cheap buliding materials as roocks, sand or watertanks. A collektor can be put on the existing wall, made of cheap greenhouse plastic plates.
A complete selfsuficent system is hard to fullfill, but a system that reduses the costs and el/fuel useage by uptil 50% is quete easy.
doc in asheville – at 04:44 I would tend to agree with Eccles (I would have a tendency to call it convection of the steam out the top :) ) - my guess is that you didn’t have the lid on tight. Another thing is that it is good to put in some hot water first to heat the inside of the container before you add the coffee.
One more thing that strikes me (being from a low pressure-high altitude place) at the lower pressures the water used to make the coffee would have boiled at a lower temperature. So the coffee itself might have not been as hot as it would normally be.
and just for fun a Thermos joke (I know there are a lot of smart blondes but this one wasn’t) A blonde woman walks into a store. Curious about a shiny object, she asks, “What is that?” The store clerk responds, “It’s a thermos.” The blonde then asks, “What does it do?” The clerk says “It keeps hot things hot and cold things cold.” So she buys one. The next day, she brings it to work with her. Her boss, also a blonde, asks, “What is that shiny object?” She replies “It’s a thermos.” He asks, “What does it do?” She says, “It keeps hot things hot and cold things cold.” He then asks, “What do you have in there?” “Two cups of coffee and a popsicle.”
Urdar-NO – at 09:29 “Solar energy, as in heating, and as a aircondition (!) is something everybody should take a look at.”
I’m not trying to be offensive, but not only is your post completely off-topic, but it assumes that everyone lives in an area where solar heating is practical. Believe me, that is definitely not reality.
Eccles, DennisC - thank you very much.
Old thread - Closed to increase Forum speed.