[Stoves] Question regarding calculations
Philip Lloyd
plloyd at mweb.co.za
Wed Sep 30 01:58:09 CDT 2015
The thermal capacity of water is not a constant. At 1 atmosphere pressure a
good correlation is
C_p(T)={4.214-2.286\times10^{-3}T+4.991\times10^{-5}T^2-4.519\times10^{-7}T^
3+1.857\times10^{-9}T^4}
https://syeilendrapramuditya.wordpress.com/2011/08/20/water-thermodynamic-pr
operties/
which, of course, you have to integrate over the delta T to get the
effective value.
https://syeilendrapramuditya.files.wordpress.com/2011/08/water_specific_heat
_capacity_vs_temperature.gif?w=540&h=330
The thermal capacity is less sensitive to pressure over the range you are
concerned about - the change to 1500m altitude will affect the 3rd decimal
place in value calculated at constant pressure.
Hope that helps
Prof Philip Lloyd
Energy Institute
Cape Peninsula University of Technology
PO Box 1906
Bellville 7535
Tel: 021 959 4323
Fax: 086 778 0257
Cell: 083 441 5247
PA: Nadia 021 959 4330
-----Original Message-----
From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Frank Shields
Sent: 30 September 2015 05:17
To: Discussion of biomass cooking stoves
Subject: [Stoves] Question regarding calculations
Greetings Stovers,
Wanting to know if it takes less energy to keep water boiling at 80 deg. C
at 1500 meters than at sea level?
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?
Thanks for any understanding help
Frank
Frank Shields
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