On Tue, 21 Jan 2014 08:08:47 -0500, Stormin Mormon
Are these pipes exposed, like the supply line for the trailer? If so,
you really need to wrap it with heat tape and insulation. If they're
buried in the floor or walls, it's a little harder. In your area you
shouldn't be worried about 20F, though.
How fast does it cool down? You can estimate your savings by taking
the average of the difference between the outside and inside
temperature (minus 10F , or so, for misc heat sources) times the time
(divided by the hours in a month, times your bill).
If the average temperature for the month is 30F and you keep the
inside at 70F, turning it down to 69F will save about 3%. Turning the
temperature down to 68F for half the time will save about the same.
On Mon, 20 Jan 2014 06:11:13 -0800 (PST), " firstname.lastname@example.org"
Windchill and wind are not the same thing. Windchill is a calculation
of the effect of wind on human skin and should be reserved for
discussing that effect. As you point out, however, wind affects other
things. Not by the evaporative effect skin is vulnerable to, but by
warm air being moved away to be replaced by cold air. In your example
above, of course the pipes could be more likely to freeze if the wind
can get to the pipes because it could lower the pipe temperature to
25. But that doesn't mean the willchill number (5F in your example)
means anything to pipes. Use another example of 40 degree air on a
very windy day. The windchill might be well below freezing, but the
pipes will never freeze because no amount of wind can lower the
temperature of a dry pipe to below the 40 degree air temperature.
Use windchill only when discussing the feel on your skin. But sealing
your house to protecting pipes from the cold air blown in by the wind
is a very good idea.
On Monday, January 20, 2014 9:32:58 AM UTC-5, Pat wrote:
No one ever said they were. But windchill together with temp are
a proxy for windspeed.
Windchill is a calculation
It's not primarily an evaporative effect on skin, unless you think people sweat
when it's 15F out. Wind produces it's chill by taking more heat away
from any object that's above ambient. That includes not only humans,
but other objects as well.
Which is the same effect that windchill has on humans, a hot brick
placed outside, or a metal pipe sticking outside a wall. YEs, it
was created as a guide to how much colder it feels to humans, but
that doesn't mean it's effect doesn't apply to cats, bricks and pipes.
In your example
It does if it's a warm pipe and it's placed outside. I have a copper
water pipe that's exposed and it runs 25 ft outside. I have some
small amount of water flow moving through it to prevent it from
freezing. Do you think the same amount of water flow that's just
sufficient to keep it from freezing when it's 20F and no windchill is
going to be sufficient to keep it from freezing when the windchill is
0F? If I told you that the windchill was 20F or 0F you would not
be more concerned about the pipe freezing in one situation versus
Use another example of 40 degree air on a
Neither I nor anyone else here ever said that windchill can cool a pipe
The fact that you don't understand that windchill has a similar effect on
objects other than humans doesn't mean it's not valuable information
that can be used in other situations. I noticed you didn't give an
answer to the simple questions posed either.
On Monday, January 20, 2014 10:51:49 AM UTC-5, Harry K wrote:
I was thinking of saying something along those lines too, but
didn't want to complicate it. I agree, evaporative effect of
cooling is going to increase with windchill. But even
in humans, I don't think the primary cooling effect is evaporation,
unless you believe people's exposed skin sweats when it's 15F.
In the winter temps
when windchill is most frequently used, I would think the main
component is that wind removes more heat from a human just like it
would more quickly remove heat from a hot brick placed outside.
In fact, in the other long thread on this, someone pointed out that
long ago when scientists first tried to come up with a windchill index,
they used water bottles exposed outside and how fast they froze.
Strange, if windchill only affects humans, how you can measure it
by how long it takes to freeze a bottle of water.
On Mon, 20 Jan 2014 10:40:34 -0800 (PST), " email@example.com"
It's reasonable to doubt this, but I think it's true.
If you check the 15F
column, a 5MPH wind lowers the perceived temp to 7F and 10MPH to 3F.
I feel like it is cheating to look it up but
The human body loses heat through convection, evaporation, conduction,
and radiation. The rate of heat loss by a surface through convection
depends on the wind speed above that surface. As a surface heats the air
around it, an insulating boundary layer of warm air forms against the
surface. Moving air disrupts the boundary layer, allowing for new,
cooler air to replace the warm air against the surface. The faster the
wind speed, the more readily the surface cools.
The speed of cooling has different effects on inanimate objects and
biological organisms. For inanimate objects, the effect of wind chill is
to reduce any warmer objects to the ambient temperature more quickly. It
cannot, however, reduce the temperature of these objects below the
ambient temperature, no matter how great the wind velocity. For most
biological organisms, the physiological response is to maintain surface
temperature in an acceptable range so as to avoid adverse effects. Thus,
the attempt to maintain a given surface temperature in an environment of
faster heat loss results in both the perception of lower temperatures
and an actual greater heat loss increasing the risk of adverse
A surface that is wet, such as a person wearing wet clothes, will lose
heat quickly because the wet cloth will conduct heat away from the body
more rapidly, and because the evaporating moisture carries away
heat. Conversely, humid air slows evaporation and makes
a surface feel warmer, and this is incorporated into longer wind chill
formulas. During warm months, this effect can be described in the heat
index or humidex.
On Monday, January 20, 2014 2:45:45 PM UTC-5, micky wrote:
Reasonable to doubt what? I didn't say that wind doesn't lower
the preceived and actual skin temperature. I just said that
I doubt the dominant factor there is *evaporation*, because IDK
about you, but my exposed skin doesn't sweat at 15F. But the
blowing wind sure carries heat off of skin, just like it does
from any other object that is above ambient, including water
Totally consistent with everything I've said. And note that they
do say it affect *inanimate* objects, which is exactly what I
have been saying and which was the main point
of contention in the previous long thread about this. You had
a certain poster claiming that windchill has no effect on
inanimate objects, which is wrong.
On Monday, January 20, 2014 8:16:11 AM UTC-5, philo wrote:
A pipe that is outside and exposed may very well freeze and
burst overnight when the windchill is severe, while it might
not burst without the windchill. Temperature isn't static.
It's typical in many locations for temps to dip down below
freezing for some period overnight. If the temperature dips
below freezing for a couple of hours, you certainly could have
instances where a pipe will freeze and burst with windchill,
while it would not without it. That's because windchill
affects how fast heat is removed from any object, not just
Wrong. The windchill index was created to reflect that but the
effects of windchill extend to any object above ambient temperature.
On Tue, 21 Jan 2014 09:31:52 -0800 (PST), " firstname.lastname@example.org"
How fast for copper? How fast for galvanized? Pex?
So when there's a windchill of 30F how cold does galvanized pipe feel?
What's the correlation with the windchill index?
Of course when it's windy there's convective heat transfer.
But the numbers used to develop the "windchill index" are based on how
human skin "feels" the wind.
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