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I'm trying to develop a portable 'Thermos' style flask that heats around 500ml of water within 1 hour for on-the-go use. Answered

I'm struggling to decide on a power source and a heating method. My tutor has suggested fuel cell technology but this is not readily available yet and although there is a lot of research on the topic, I have to create a working model. Any ideas would be greatly appreciated?



Thanks for all your answers - much appreciated.

I need it to heat 500ml of water to around 80C (enough for a hot beverage) so that the user can then add instant coffee/tea. I've looked into the technology behind zippo handwarmers using lighter fuel and a catalytic converter. I must either have a working model or perhaps just a prototype with a separate model simulating the technology within the flask.

I need it to be fairly innovative so using batteries wouldn't work for this (plus it would be too bulky).

Thanks again!

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ey14 (author)2012-03-08

Thanks for all your answers - much appreciated.

I need it to heat 500ml of water to around 80C (enough for a hot beverage) so that the user can then add instant coffee/tea. I've looked into the technology behind zippo handwarmers using lighter fuel and a catalytic converter. I must either have a working model or perhaps just a prototype with a separate model simulating the technology within the flask.

I need it to be fairly innovative so using batteries wouldn't work for this (plus it would be too bulky).

Thanks again!

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user
steveastrouk (author)2012-03-08

Are you allowed flame sources ?

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ey14 (author)steveastrouk2012-03-08

Nothing to say I can't, however, safety is a big element

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steveastrouk (author)ey142012-03-08

Whatever, you have to dump a LOT of energy into a water based system to increase its temperature.

I was thinking of something like a Kelly kettle.
http://en.wikipedia.org/wiki/Kelly_Kettle

but with Rick's catalytic technology instead. Perhaps the guts of a gas soldering iron or hair tongs.


Steve

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mpilchfamily (author)2012-03-08

How hot does it have to get?

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ey14 (author)mpilchfamily2012-03-08

Around 80C - hot enough to mix with instant coffee/tea

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bwrussell (author)2012-03-08

You could use a Peltier unit. Typically they are used to cool things but just flip it over and you can use it to heat.

How hot you want to get the water would be helpful to know. Resistors are a possibility but may only be able to heat to 'warm' and not 'hot'.

There are also chemical options, like what is used to heat MRE's.

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steveastrouk (author)bwrussell2012-03-08

Why only "warm" not hot ?

Here's a picture of my 3100F furnace, heated with only "resistors"

Steve

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bwrussell (author)steveastrouk2012-03-08

Of course it is possible but it is not practical for this application.

You need 40 Wh to heat .5L of water from 15C to 85C. Using 9V batteries you would need around 8 batteries to heat the water once. Alternatively you could use 1.5 V and then you would need around 3 Ds, 4 Cs, or 12 AAs. Finding a suitable power source is going to be a problem no matter the electrical heating source. I think the flame-less heaters from a MRE might be a good choice.

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steveastrouk (author)bwrussell2012-03-08

Then you should have qualified what you said about resistors by talking about the power source first.

Steve

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mpilchfamily (author)bwrussell2012-03-08

My avatar is a picture from a PSU load tester i built about 6 years ago. Those resistors got pretty darn hot when i would select a 30A load on the 12V rail. If it wasn't for the massive heat syncs and all the airflow i had in the system it probably would have fried an egg.

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bwrussell (author)mpilchfamily2012-03-08

30A and 12V isn't really an option for portable. If a sort of docking station to heat the thermos before leaving was an option then resistive is an option.

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rickharris (author)2012-03-08

Chemical heating - look into the hand heater type of energy cell.

alternatively there used to be a hand warmer that got pretty hot using lighter fuel and a catalytic burner to burn off the fumes - once light the heater ran until the fuel was exhausted with too a couple of hours.

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