From: Michael S. Lorrey (retroman@turbont.net)
Date: Tue Aug 29 2000 - 07:35:58 MDT
Damien Broderick wrote:
>
> At 09:54 AM 28/08/00 -0400, Mike wrote:
>
> >Since I've seen camping coolers that use a small solar panel to power a solid
> >state cooling device, I would imagine that a still suit would have PV
> devices to
> >power the cooling of collected water by similar means...
>
> But they'd be damned hot to wear, in turn, I think.
>
> A data point: evaporating/venting one gram of water takes off 2.4
> kilojoules of heat. I don't know how that would compare with slowly raising
> the temperature of a capillary mesh of liquid helium (4.2 degrees K) or
> whatever.
I don't know why they'd be hot to wear. Solar cells are actually rather light,
as are these thermocouples I'm talking about. Utilizing heatsinks behind the
solar cell, venting air up through a sink that has a large amount of surface
area (as much as ten times the surface area of the device footprint) would
dissipate any extra heat in the system. Lets say you have a 20cm x 50cm heat
exchanger on your back, that has a radiative surface area of 1 sq meter. Human
skin evaporating sweat is actually far less efficient than the standard black
body (unless of course, that skin is itself black, which is another thing
entirely), and yanking heat from the body via a fluid cooling system to be
cooled by a combo of the heat exchanger and solid state thermocouples powered by
solar cells (likely mounted on a hat or sunshade).
Does anyone know to what degree the tan or tint a person has in their skin aids
them in cooling? Does dying your skin dark help measurably?
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