Wind chill and frozen pipes again

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On Wednesday, January 22, 2014 7:00:08 AM UTC-5, micky wrote:

Yeah, good idea. Focus on that instead of the fact that you have the science wrong.

Good grief is an insult? What you don't like is being told that you're wrong and having it explained to you. Otherwise, you'd be discussing and replying to the two examples I just gave you. Wind removes heat from exposed skin via convection, just like it does from any object that is above ambient temperature. Evaporation is not necessary. The cooling of exposed skin is *not* driven primarily by evaporation, unless you're sweating when it's 15F out. Seems hundreds of millions of years of evolution has figured that out. It's driven by convection, just like using *moving* air through a car radiator works. And BTW, I figured the good grief was appropriate because I've clearly explained this to you ten times now, here and in the other thread. CL told you the same thing.
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On Wed, 22 Jan 2014 05:05:32 -0800 (PST), " snipped-for-privacy@optonline.net"

One would think that with a growing number of voices in opposition to your "science" that there may be a chance you have it wrong.
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On Wed, 22 Jan 2014 08:46:33 -0600, Gordon Shumway

Sorry, but in this case, Trader is 100% correct.
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On Wednesday, January 22, 2014 11:57:51 AM UTC-5, snipped-for-privacy@attt.bizz wrote:

Thanks for the support. And I'd also point out that I'm not impressed by the number of voices. It's not the number, it's if what they are saying follows physics or is just nonsense. If a growing number of people say that V=IR^2, does that make it right? good grief.
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On Thu, 23 Jan 2014 10:29:16 -0800 (PST), " snipped-for-privacy@optonline.net"

V=IR

Apparently it makes Global Warming "right".
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<stuff snipped>
It pains me to do this, but Trader's right about this. The concept of higher air flow resulting in greater heat transfer is the guiding principle behind the calculation of the wind chill index. Any restrictions placed on what wind chill means are irrespective of the science behind its calculation.
The clearest example I can think of heat transfer via moving air is like Trader's car fan example. Faster computer CPU speeds (and power consumption) forced the industry to mount fans atop their CPUs. They did that because passive cooling, even from massive heat sinks, caused the faster CPUs to burn up. Moving air removes heat more quickly than still air, whether it's a CPU, a pipe or a human being. Hair dryers would incinerate themselves without a fan to transfer heat from the heating coils.

from any object

Correct, but evaporation does play a small role, as do many other things. Ask yourself whether you'd rather be stranded outside at 0F with a wet jacket or a dry one. (-: (And yes, I know that wet clothes transfer heat more rapidly than dry ones and insulation loses R-value when wet.)
Evaporative cooling is more important to windchill's fraternal twin, the heat index. That's when sweating in a humid environment does not cool the skin well and so 100F degrees in Atlanta or DC can feel like 110F in the desert. It seems that the two concepts got slightly mashed up in this thread. There's fascinating reading at:
http://en.wikipedia.org/wiki/Wind_chill
that describes a number of controversies associated with calculating wind-chill, windchill, wind chill, wind chill index or the wind chill factor (the fact that no one can agree what to call it speaks volumes about its controversial nature).
<<The method for calculating wind chill has been controversial because experts disagree on whether it should be based on whole body cooling either while naked or while wearing appropriate clothing, or if it should be based instead on local cooling of the most exposed skin, such as the face. The internal thermal resistance is also a point of contention. It varies widely from person to person. Had the average value for the subjects been used, calculated WCET's would be a few degrees more severe. The 2001 WCET is a steady state calculation (except for the time to frostbite estimates).[13] There are significant time-dependent aspects to wind chill because cooling is most rapid at the start of any exposure, when the skin is still warm.>>
While there can be some defintional arguments about whether wind chill can be used when discussing non-human objects, there's no argument that air moving over something will transfer heat faster than no air movement.
Generally, wind chill cannot lower the temperature of something lower than the ambient temperature *unless* there's enough liquid evaporating (think Great Lakes) to account for a substantial temperature drop. If my wife hadn't declared a moratorium on freezer-related experiments, I would even try hooking up some thermocouples to both wet and dry pipe sections in the freezer to see whether a wet pipe had a noticeable temperature difference due to evaporation. Maybe some bachelor will do "the science" for us. (-:
Definitional purists would be correct in saying that wind chill does not apply to inanimate objects but the scientific formula for computing it still remains in place and that says the faster the wind, the greater the heat transfer. For humans, pipes, dogs and CPU's alike.
The Aussies have created an AAT (Aussie Apparent Temperature) just to confuse things further.
http://www.weather-watch.com/smf/index.php?topicR051.0
--
Bobby G.



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On Thursday, January 23, 2014 8:36:06 AM UTC-5, Robert Green wrote:

Thank you for the support. It's good to see we can agree on something.
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I was doing some more sealing cracks at my old house. The wind gets into them.
Greg
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On 1/21/2014 12:19 AM, gregz wrote:

Caulk is good, and that "great Stuff" foam is also good. I figure any where cold air blows in, hot air has to be blowing out the other side.
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Christopher A. Young
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