Wind chill describes rate of heat loss of objects. Doesn't matter if they are living or dead. Ask the pilots in alaska, if wind chill is important when they land a plane in cold weather. Wind chill has a big effect on how long they can be there, before the oil is too cold to allow the plane to restart.
In the case of water pipes, it has a big effect on how fast they freeze. Which is the question of this thread.
You have it exactly.
Wind chill affects the RATE of heat loss, not the temperature an object will cool down to.
If you put an inanimate object, like a cinder block, outdoors then it will cool down to the ambient temperature. The stronger the wind, the higher the wind chill, and the faster that cinder block will cool down to the ambient temperature, which is the temperature without considering wind chill.
People experience heat loss from their skin as the sensation "cold". The more rapidly heat is lost from the skin, the colder it feels to us. So, an outdoor temperature of -20 deg. F. can "feel like" an outdoor temperature of -30 deg. F. if there is a wind. The wind accelerates heat loss from the skin, thereby making it "feel" colder to us.
However, long story short, an inanimate object will never cool down to a temperature below the ambient temperature because of the wind. Lack of any wind will just mean that it will take longer for that inanimate object to cool down to ambient temperatures.
And, wind chill works in the opposite direction as well. If you defrost your fridge and put the ice outside on a warm summer day to melt, the stronger the wind, the faster that ice will melt. The less wind there is, the longer it will take that ice to melt.
So evaporative cooling doesn't really work?
We're gonna have to disagree on that. The thermodynamics are the same, but the conditions are very different. The number scrolling across your TV screen and what's happening inside the walls of your house may be different and different from what's happening inside the walls of my house.
I would disagree with that somewhat. I believe that an inanimate object, say a cinder block for instance, if soaked in water and exposed to wind in low humidity, will reach a temperature somewhat below ambient until all the water evaporates.
Well, you're making up different conditions. Pipes don't have humidity, unless they're very leaky.
And that's the whole point of this pissing contest. Wind chill is a made up number based on empirical experiments on humans using measurements at the airport, looked up in a table, and posted on your TV screen.
The other way to get it is to calculate it directly from your own measurements inside your walls and that table lookup. But if you have those measurements, use 'em. Don't make up another number you don't need.
You can certainly imagine cases where wind blows directly on the pipes. If you live in a cold climate that's a no-no.
Right now it's 31F outside. My crawl space is at 54F. And it will be close to 55F next week and in June. And that's not by accident. The ground temp is very stable, and I don't let the wind blow under there.
Changing the subject... There's an experiment you can do. Turn off the water and wait several hours for it to stabilize. The water at different points in the system may be at different temperatures.
Take a small container, like the lid of a spray can and stick a thermometer in it. Turn on the water into the container. You can see the temperature change as water from different parts of the pipe reaches the spigot. There's a tradeoff. You want it to flow fast, so the temperature changes little along the way, but not so fast that the thermometer can't keep up. The further the distance, the less the accuracy.
I did the experiment a few weeks ago when we had record low temps around 15F. Water never got below 50F. And that happened just where it should have where the pipe goes thru an area closest to an outside wall.
When you want an answer, make a direct measurement on the thing you're measuring. Conditions at the airport aren't very direct when you have rivers and hills in between.
'Nother change of subject. My neighbor had his water meter changed. I got there late, so didn't see the start, but they put a collar around the pipe, pumped something cold into it to freeze the water so they could remove the meter. Way cool...
Such as a "wet bulb" used in sling psychrometers. Will never cool below ambient, right? Or, a wet beach towel, hung from a line, or a media pad in a swamp cooler, or a wet forehead, under a brim of a hat.
I've heard of electric operated "pipe freezer" for this. May also have been some eco friendly low boiling point suff like freon, or carbon dioxide.
BS as already proven with the simple examples:
A brick that's 75F when placed outside when it's 20F is going to cool faster with a windchill of 0F, than with a windchill of
15F. A house is going to take more energy to keep it warm on a night when the windchill is 0F, than when the windchill is 20F, even if the outside temp both nights is 20F. That's because windchill has a direct bearing on how heat is removed from any object, without regard to whether it's alive or not.
You only get wind chill if there is wind. Go look at the formula for the USA. The only components are temp and wind speed. Wind chill cools that brick or house cited in the example.
And in the context of the discussion, I'll ask the simple question again. If you have water pipes in a crawlspace that has some vent openings, drafts, etc and it's 20F outside, are those pipes more likely to freeze on a night when the windchill is 0F or when it's 20F?
Until you can understand the difference there is no
Nonsense. Why would windchill only remove heat from things that are alive? Good grief.
If I may paraphrase, you're as dumb as the brick in the example.
Failure to answer the simple, direct question noted. That's a sure sign that you know you're wrong.
Wow Stormy, you're knockin them outta the park this morning. ;-)
I agree and it's a valid point. But that doesn't mean that windchill index doesn't have an effect on inanimate objects, which is what Gordon is claiming. Here is the context of the original question:
"Tonight in NYS supposed to be 0F, and wind chill -10 or so. Which number is the one which concerns water pipes freezing?
I know the pipes won't get below the actual temp, but are they more likely to freeze, with wind? "
So, you have Gordon claiming windchill has no effect on inanimate objects. Listening to that, should Stormin conclude that there is no possible effect of that lower reported windchill on pipes in a crawlspace? That is what Gordon is claiming, forget about the windchill, it only effects inanimate objects.
I would say it's going to have an effect if it's moving cold air from outside into the crawlspace. That happens if there is wind, which is reflected in the reported windchill index. Even if the air doesn't make it inside, the temp inside the crawlspace is likely to be lower with a higher windchill, because it's moving around the outside of the foundation too. Therefore, in certain conditions, the lower the windchill, the more likely it can be that pipes will freeze.
Many factors come into play on how the wind moves
It could very well determine if they will freeze. Let's say you forgot to drain the pipes and won't be back for a day. If the temps go below freezing overnight, down to 20F, with a significant reported windchill, the pipes in the crawlspace may freeze. With no windchill, they might not have enough time to freeze before the temp rises again in the morning.
Rate of heat transfer is the only
I agree and never suggested otherwise. Note that rate of heat transfer is an effect on inanimate objects.
Which shows that windchill applies to inanimate objects too.
Here is my last hope at getting you to understand the difference between "Wind" and "Wind Chill."
Pay particular attention to the frequently asked question number 12.
If point #12 does not settle this argument once and for all, nothing will!
Oh, no it won't! ;-)
Pay particular attention to the fact that just like you, they contradicted themselves. Anyone can see that:
"Q: Does wind chill only apply to people and animals?
Yes. The only effect wind chill has on inanimate objects, such as car radia tors and water pipes, is to more quickly cool the object to cool to the cur rent air temperature. Object will NOT cool below the actual air temperature . For example, if the temperature outside is -5 degrees Fahrenheit and the wind chill temperature is -31 degrees Fahrenheit, then your car's radiator will not drop lower than -5 degrees F."
First they say it only applies to people and animals, then they say windchill does affect radiators and water pipes. Which of course is exactly what I and other here have been saying. They say it has an effect. What you said was:
"Wind chill" has absolutely no effect on inanimate objects."
Thanks for proving my point.
It does settle it. They clearly say that windchill does have an effect on radiators and "water pipes", causing them to cool faster. Radiators and water pipes are inanimate objects. Therefore, Gordon's statement:
"Wind chill" has absolutely no effect on inanimate objects."
is clearly wrong. Precisely what I've been saying.
Wind, NOT wind chill (two words) has an effect on everything cooling faster.
Wind chill is just a number in a chart!
I'm done.
In the scenario at hand, does jacking up the interior heat mean much if you are worried about a pipe on an outside wall? I am away and have already jacked the temp from the standard 50 to around 70 (thanks WiFi thermostat). Any real reason to kick it up further.
Reread FAQ 12. Their statement is, 'The only effect wind chill has on inanimate objects, such as car radiators and water pipes, is to more quickly cool the object to cool to the current air temperature. Object will NOT cool below the actual air temperature.' I know in their first statement they confirmed wind chill only applies to people and animals, but they can't have it both ways.
It appears you and the NWS are not in agreement either.
Perhaps it would be more accurate to say wind chill temperature only applies to people and animals since it describes a felt condition (I don't subscribe to the idea that inanimate objects 'feel'). And, that wind chill describes the condition where the wind sucks the heat out of anything.
Whatever.
My belief of question number two is that it is just a minor glitch similar to what the obamakare web site has.
I totally agree with your first sentence.
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