## Re: Quick clarification on convection

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• I think you are right Jamie, from wind it would be convection. if you are laying on the pad and heat is leaving the bottom of the pad then it would be a
Message 1 of 5 , Apr 4 4:50 PM
I think you are right Jamie, from wind it would be convection. if you
are laying on the pad and heat is leaving the bottom of the pad then
it would be a combination of convection and conduction. conduction
would be the heat from your body the pad lets through for convection
to then take on off. This of course assumes that the underside (air)
is colder than you on the top side.

Coy Boy

--- In hammockcamping@yahoogroups.com, "chcoa" <jdeben@...> wrote:
>
> Hi all,
>
> I'm writing a report for BGT on the Women't ProLite I'm testing. I'm
> about to include a section on how it performed as bottom insluation in
> my hammock with a reference to heat loss via the wind. I was going to
> call this convection then I started second guessing myself and even
> though I looked it up, I'm not entirely sure convection is the right
> word to describe heat loss via wind.
>
> Will someone who knows clarify for me please?
>
> Thanks
> jamie d
>
• Choca, Heat transfer can get confusing and it is difficult at times to determine whether radiation, conduction or convection is the primary means. Convection
Message 2 of 5 , Apr 4 6:04 PM
Choca,

Heat transfer can get confusing and it is difficult at times to
determine whether radiation, conduction or convection is the primary
means. Convection is fluid movement, with natural convection (in
air) being warm air rising because it is lighter and being replaced
by cooler, heavier air. This replaces your boundary layer of warm
air at some rate that primarily depends on the temperatures
involved. Wind is sometimes referred to as forced convection where
wind currents rapidly replace your boundary layer of warm air. I'm
calling the boundary layer of warm air as the layer of air on the
outside of your insulation that you warm up some in still air.

But, you may be talking of wind currents actually flushing warm air
out of your insulation. Air mats are immune to that since they are
air tight. Some types of highly breathable insulation, like most of
the sleeping bags we use, are not immune to that and their
susceptibility is inversely proportional to how breathable they are.
I would call this how wind proof versus breathable it is rather than
labeling it as some form of convective heat transfer. Wind proofness
is a good thing in cooler, windy conditions while high breathability
is a good thing in warmer, stagnant conditions... usually we are in
the middle ground where it is six-of-one versus half-a-dozen of the
other.

Hope I didn't confuse you.

Dave

--- In hammockcamping@yahoogroups.com, "Coy" <starnescr@...> wrote:
>
> I think you are right Jamie, from wind it would be convection. if
you
> are laying on the pad and heat is leaving the bottom of the pad then
> it would be a combination of convection and conduction. conduction
> would be the heat from your body the pad lets through for convection
> to then take on off. This of course assumes that the underside
(air)
> is colder than you on the top side.
>
> Coy Boy
>
> --- In hammockcamping@yahoogroups.com, "chcoa" <jdeben@> wrote:
> >
> > Hi all,
> >
> > I'm writing a report for BGT on the Women't ProLite I'm testing.
I'm
> > about to include a section on how it performed as bottom
insluation in
> > my hammock with a reference to heat loss via the wind. I was
going to
> > call this convection then I started second guessing myself and
even
> > though I looked it up, I'm not entirely sure convection is the
right
> > word to describe heat loss via wind.
> >
> > Will someone who knows clarify for me please?
> >
> > Thanks
> > jamie d
> >
>
• ... Some types of highly breathable insulation, like most of ... Opps! Should have said ...susceptibility is proportional to how breathable they are.
Message 3 of 5 , Apr 4 6:44 PM
--- In hammockcamping@yahoogroups.com, "Dave Womble" <dpwomble@...>
wrote:
>
Some types of highly breathable insulation, like most of
> the sleeping bags we use, are not immune to that and their
> susceptibility is inversely proportional to how breathable they are.

Opps! Should have said "...susceptibility is proportional to how
breathable they are."
• Thanks guys. I ll stick with convection so it s more simple for the readers of my report. I don t want anyones head to explode with all the complexities of
Message 4 of 5 , Apr 4 9:32 PM
Thanks guys. I'll stick with convection so it's more simple for the
readers of my report. I don't want anyones head to explode with all
the complexities of this stuff. :)

jamie in az
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