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Dear Frank</div>
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Thanks for clarifying that. </div>
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It doesn't take any energy to keep water hot. It is only necessary to overcome the losses from the pot by radiation, convection and conduction, the last being negligible. </div>
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Prof Annegarn showed that the heat lost from the pot is dominated by the colour and surface texture. If you overcome that it remains hot. </div>
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It makes no difference what quantity of water is in the pot. This was shown with a high degree of precision - four 9's - by Yixiang Zhang at CAU. </div>
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Regards </div>
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Crispin </div>
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<div class="PlainText">Dear Stovers<br>
Re-read my question and now see the problem. I ment to say ' keep water at 80c' and does that require the same energy at sea level as it does at 1500 meters? Sorry. Not 'boiling'!<br>
<br>
Maintain a boil at 1500 meters takes less energy than boil at sea level I think.<br>
<br>
And ask one question leads to ten more. <br>
<br>
Thanks<br>
Frank<br>
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<br>
Sent from my iPhone<br>
<br>
> On Oct 4, 2015, at 2:18 PM, ajheggie@gmail.com wrote:<br>
> <br>
> [Default] On Tue, 29 Sep 2015 20:17:29 -0700,Frank Shields<br>
> <franke@cruzio.com> wrote:<br>
> <br>
>> Greetings Stovers, <br>
>> <br>
>> Wanting to know if it takes less energy to keep water boiling at 80 deg. C at 1500 meters than at sea level?<br>
> <br>
> Frank I've waited before ploughing in because I couldn't understand<br>
> the reasoning behind your question.<br>
> <br>
> The thing is at 1500 metres above sea level the pressure is still 96%<br>
> of pressure at sea level, so to boil water you have to raise the<br>
> temperature of water until it's vapour pressure equals the ambient air<br>
> pressure, and that is at 98.6C<br>
>> <br>
>> Also; It take 4.186 j/g/deg.C to raise water from 20c to 80c at sea level. But is it the same at 1500 meters? or is it less than 4.186?<br>
> <br>
>> From Prof Lloyd's post the specific heat of water varies with<br>
> temperature and is probably thus not variable with pressure.<br>
> <br>
> So my view would be to keep water at 80C at 1500 metres asl in a<br>
> saucepan with tight fitting lid, so no vapour escapes would be the<br>
> same power as at the same ambient temperature as at sea level.<br>
> <br>
> AJH<br>
> <br>
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