In article <4pr3sp$...@pollux.usc.edu> k...@pollux.usc.edu (Kenneth J. Hendrickson) writes:
>Curiosity got the better of me, and I started to do some back of the
>envelope scratching to find out how effective ECA is. Thermo is not my
>strong suit, so I'm posting here asking for help from the MEs and P-Chem
>folks.
>ECA raises my temp from about 97F to 99F, or from about 309K to 310K.
I always wondered about how much the ECA stack was supposed to raise
one's body temperature--when I take it my temperature tends to go
from, say, 96.7 all the way up to 96.7. (I don't take it often and
I don't ever consume caffeine otherwise, but as long as I only use
it occasionally, it does seem to make my workouts go better even if
it doesn't have any effect on body temperature.) (It also works
great at keeping me from having a sore throat after a long bike
ride.)
>I seem to remember that the energy in any harmonic oscillator is
>proportional (via the Boltzmann constant, k=1.380*10^-16 erg/K) to
>absolute temperature. I also seem to remember that the energy
>radiated from a black body is proportional to absolute temperature
>to the fourth power.
Yup; however, neither of these are particularly relevant to the
situation you describe.
>Calories are units of energy.
>I want to do a thermodynamic analysis of how much extra fat is being
>burned due to the ECA stack.
>Assumption 1: My energy requirements are 2000 Cal/day.
>Assumption 2: My temperature remains constant.
>Assumption 3: My environment remains constant, and unchanged.
>Model 1: I'm like a harmonic oscillator, and the extra energy
> required to raise my temperature comes from burning
> extra fat. This extra energy is directly proportional
> to the increase in my absolute temperature.
> My new energy requirements are 2000 * (310/309) = 2006
This model is really only considering the energy cost of raising your
temperature from one value to another, not maintaining it; a better
way of calculating this effect would be to figure out how many
kilocalories (food calories) are required to raise the temperature of
an equal mass of water by the same amount (and, for these purposes, it
is reasonable to approximate a human body as a similarly sized quantity
of water). So, if you weighed 70Kg and your temperature were to rise
by 1 degree celsius, that alone would consume 70 kilocal--ignoring, of
course, any effects that the ECA stack might have on the processes that
remove heat from your body (does ECA affect sweating, for example, during
the time your temperature is increasing?).
>Model 2: I'm like a black body, and the extra energy I radiate
> comes from burning extra fat. This extra energy is
> proportional to the increase in my absolute temperature
> raised to the 4th power.
> My new energy requirements are 2000 * (310/309)^4 = 2026
Again, this is likely to be a negligible factor unless you happen to
be floating in vacuum. Black-body radiation is normally a remarkably
tiny portion of cooling unless 1) you happen to be in vacuum (which
could pose some health problems of its own) or 2) you're astoundingly
hot (ditto). This is the reason that heat disposal can be very
difficult in space.
>Have I totally misunderstood the thermodynamics involved, or is ECA
>really this ineffective? What of the studies that show increased fat
>loss in those supplementing their diet with the ECA stack? Can the
>extra fat loss be thermodynamically explained, or are other factors such
>as appetite suppression and/or placebo effect responsible?
Well, you've neglected the main mechanisms of cooling (conduction,
convection, and evaporation (sweating)), all of which are many orders
of magnitude more significant than radiation; conduction (and, to
some extent, convection, but that's really quite a bit more complex)
is proportional to the temperature difference between you and your
surroundings, so going from 97 to 99 with an ambient temperature of
70 is about a 7.4% increase, and you don't have to worry about
absolute temperatures unless your room happens to be at absolute
zero (I should, once again, caution that this can have health
risks of its own).
My guess is that the extra calories burned at higher body temperatures
result primarily from 1) the increased reaction rate experienced by the
various chemical processes in your body at the higher temperature,
2) the energy cost of sweating (which does take some energy to do), and
3) the higher activity levels (which may just include fidgeting)
generally exhibited by people under the influence of stimulants.
As far as actual weight lost, more than anything, this may result from
1) the appetite-suppressing effects of ephedrine and caffeine and
2) the diuretic effects of ephedrine and caffeine (which is just water
weight). Your milage may vary, of course, but I think it likely that
these two effects contribute more to weight loss than the increased
energy expenditure.
--
Trygve Lode | 6529 Lakeside Circle, Littleton CO 80125 | (303) 470-1011
Want a copy of the soc.singles FAQ? Send mail to tl...@nyx10.cs.du.edu
"Always remember: day follows day, but night precedes night, and your
hands are just microscopes for pencils to look through." -- Bill Knott
