Wind chill and frozen pipes again

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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.
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On Mon, 20 Jan 2014 16:04:20 -0800 (PST), Bob_Villa

Okay. So it's the temperature in practice. Which is affected by all the factors.
It makes sense. I know pipes don't burst the moment the temp hits 32, or even 31.
Thanks.
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On Mon, 20 Jan 2014 06:11:13 -0800 (PST), " snipped-for-privacy@optonline.net"

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.
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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 the other?
Use another example of 40 degree air on a

Neither I nor anyone else here ever said that windchill can cool a pipe below ambient.

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.
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On 1/20/2014 8:16 AM, philo wrote:

But..........in windier conditions, a structure that isn't sealed up tight would likely get colder inside than it would without wind.
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wrote:

Stormy's "redneck bungalow" will loose heat a lot faster in the wind than on a still day of the same temperature.
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On Monday, January 20, 2014 5:16:11 AM UTC-8, philo  wrote:



And if that pipe is kept wet and exposed to the breeze?
Harry K
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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.
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On Mon, 20 Jan 2014 10:40:34 -0800 (PST), " snipped-for-privacy@optonline.net"

It's reasonable to doubt this, but I think it's true.
http://en.wikipedia.org/wiki/File:Wind_chill.png 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 http://en.wikipedia.org/wiki/Windchill
The human body loses heat through convection, evaporation, conduction, and radiation.[1] 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 effects.[citation needed]
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.[citation needed] 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.
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wrote:

It is heat loss by CONDUCTION that is affected by wind "chill" as it strips off the "boundary layer" of warm air that naturally clings to the body.

How FAST is the critical point. How FAST does a bottle of water at 96F freeze???? The windier it is, the faster it will freeze at any given temperature (32F or below)

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On Monday, January 20, 2014 2:45:45 PM UTC-5, micky wrote:

re.

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 pipes.

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.

Again, totally consistent.
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On Monday, January 20, 2014 8:16:11 AM UTC-5, philo  wrote:

Sure

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 humans.

Wrong. The windchill index was created to reflect that but the effects of windchill extend to any object above ambient temperature.
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On Tue, 21 Jan 2014 09:31:52 -0800 (PST), " snipped-for-privacy@optonline.net"

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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On Tue, 21 Jan 2014 12:18:46 -0600, Vic Smith

Faster for copper than galvanized, and faster for galvanized than PEX because of the difference in heat transfer between the 3 materials.

Galvanized or whatever will never feel colder than ambient - wind or no wind - but it will get down to ambient more quickly in the wind.
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On Tue, 21 Jan 2014 17:01:13 -0500, snipped-for-privacy@snyder.on.ca wrote:

Now, don't keep sayin' that! Trader4 is gonna start callin' you a liar and all kinds of other stuff too. Don't say I didn't warn you.
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On 1/21/2014 7:16 PM, Gordon Shumway wrote:

Oh, gosh. Then we'll have people killfiling each other right and left. It will be the wild west, all over again. I got my low slung, tied down filter. Don't make me slap mouse on you, rustler.
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Christopher A. Young
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On Tue, 21 Jan 2014 19:30:59 -0500, Stormin Mormon

Oh yeah, I'll sick my two cats on yer mouse, you sidewinder!
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On Tue, 21 Jan 2014 18:16:27 -0600, Gordon Shumway

Trader's called me worse, but unless someone replies to him I won't see his posts.
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On Tue, 21 Jan 2014 20:00:31 -0500, snipped-for-privacy@snyder.on.ca wrote:

Yup, it's just like stormy predicted. Kill files are flying left and right!
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On Tue, 21 Jan 2014 21:25:49 -0600, Gordon Shumway

Trader's been on my list for months.
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