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Post by koshka on Jan 19, 2017 16:28:44 GMT
It seems like every winter, there's an argument over whether wind chill has any effect on nonliving things -- most commonly, whether sub-zero wind chills are as rough on a car as sub-zero temperatures.
Testing this could get tricky, assuming the new show is being filmed in California it would call for either a wind tunnel with refrigeration equipment or a road trip.
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Post by GTCGreg on Jan 19, 2017 16:45:37 GMT
It seems like every winter, there's an argument over whether wind chill has any effect on nonliving things -- most commonly, whether sub-zero wind chills are as rough on a car as sub-zero temperatures. Testing this could get tricky, assuming the new show is being filmed in California it would call for either a wind tunnel with refrigeration equipment or a road trip. Wind chill will cause a warmer object to get colder faster, but once that object reaches the ambient temperature, wind chill isn't going to have any further effect. Now if your nonliving thing has some kind of internal heat source trying to keep it warm, then yes, the wind chill factor will have an effect. As for testing, I think the only thing you can do is monitor the temperature of the object and see how fast the temperature falls off. But again, once it reaches ambient, the temperature isn't going to change with or without wind.
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Post by Cybermortis on Jan 19, 2017 20:54:21 GMT
Hello and welcome to TC.
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Post by WhutScreenName on Jan 19, 2017 21:18:48 GMT
One thing I always thought about wind chill and cars... IF wind chill is bad for a car... wouldn't driving it in the cold be just as terrible or worse? I mean, when driving, there's a significant amount of cold air being forced into the grill of the car. Or, does this only impact a car before it's started?
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Post by the light works on Jan 19, 2017 23:35:13 GMT
It bears mentioning that for living things, wind chill becomes wind heating when the air temperature exceeds the thing's body temperature.
but yes, as the others have said, wind chill acts differently on nonliving things, because instead of a matter of how much energy must be expended to maintain normal body temperature, it is a matter of how quickly they reach ambient temperature.
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Post by GTCGreg on Jan 19, 2017 23:49:06 GMT
It bears mentioning that for living things, wind chill becomes wind heating when the air temperature exceeds the thing's body temperature. but yes, as the others have said, wind chill acts differently on nonliving things, because instead of a matter of how much energy must be expended to maintain normal body temperature, it is a matter of how quickly they reach ambient temperature. Unless the humidity is really high, a wind on a hot day helps evaporate sweat and promotes cooling. That is if the living thing sweats. Some don't and in those cases, the wind may, as you say, cause more rapid heating.
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Post by the light works on Jan 20, 2017 0:04:25 GMT
It bears mentioning that for living things, wind chill becomes wind heating when the air temperature exceeds the thing's body temperature. but yes, as the others have said, wind chill acts differently on nonliving things, because instead of a matter of how much energy must be expended to maintain normal body temperature, it is a matter of how quickly they reach ambient temperature. Unless the humidity is really high, a wind on a hot day helps evaporate sweat and promotes cooling. That is if the living thing sweats. Some don't and in those cases, the wind may, as you say, cause more rapid heating. if it sweats sufficiently to maintain cooling. I can say for a fact that over 100 degrees at 70 MPH with bare fingers feels like riding into an oven. but it occurs to me, a good test of wind cooling on a machine is simply a liquid cooled engine with a variable speed radiator fan. it has all the parts you need: a heat source, a wind tunnel, and a heat exchanger. add a couple thermocouples and you're golden.
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Post by GTCGreg on Jan 20, 2017 0:24:55 GMT
Unless the humidity is really high, a wind on a hot day helps evaporate sweat and promotes cooling. That is if the living thing sweats. Some don't and in those cases, the wind may, as you say, cause more rapid heating. if it sweats sufficiently to maintain cooling. I can say for a fact that over 100 degrees at 70 MPH with bare fingers feels like riding into an oven. but it occurs to me, a good test of wind cooling on a machine is simply a liquid cooled engine with a variable speed radiator fan. it has all the parts you need: a heat source, a wind tunnel, and a heat exchanger. add a couple thermocouples and you're golden. But do you really want a heat source? Without question, wind speed will affect the amount of heat being removed from a heat source. But I thought the whole idea of nonliving object, such as a car that has been sitting all night, is that there is no internal heat source. Add a heat source and that changes everything.
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Post by the light works on Jan 20, 2017 1:38:48 GMT
if it sweats sufficiently to maintain cooling. I can say for a fact that over 100 degrees at 70 MPH with bare fingers feels like riding into an oven. but it occurs to me, a good test of wind cooling on a machine is simply a liquid cooled engine with a variable speed radiator fan. it has all the parts you need: a heat source, a wind tunnel, and a heat exchanger. add a couple thermocouples and you're golden. But do you really want a heat source? Without question, wind speed will affect the amount of heat being removed from a heat source. But I thought the whole idea of nonliving object, such as a car that has been sitting all night, is that there is no internal heat source. Add a heat source and that changes everything. right. add an electric cooling pump, and then you can compare both cooling-to-ambient AND temperature maintenance factors. - but even with cooling to ambient, you want a heat source to reheat it for the tests.
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Post by silverdragon on Jan 20, 2017 7:46:44 GMT
It seems like every winter, there's an argument over whether wind chill has any effect on nonliving things -- most commonly, whether sub-zero wind chills are as rough on a car as sub-zero temperatures. Testing this could get tricky, assuming the new show is being filmed in California it would call for either a wind tunnel with refrigeration equipment or a road trip. Hello and welcome to TC. Yes this is worth testing, if only to show people how much it works. -10 outside is still -10 outside, but if its getting colder due to there being a wind coming from a place that is -20 outside, and the wind is therefore -20, then even though its -10, the wind is going to cool it down quickly. The ambient themp of the place you are in and the temp of the wind blowing across it can be that different... and more.... And I suggest a wind tunnel with a chiller on it to blow a cold wind over a static thermometer to see how fast it cooled down with or without the fan running, and at different speeds of fan. Just to put discussion in to others on the board, here in UK, we have North Sea, and Scandinavia to one side, if the wind comes from the north, its the land and seas to that side of the country that dictate the temp of the wind. If from the south or south west, we have gulf stream seas and european continent that "usually" supply warm winds. Wind chill can go to wind warmth and back again, all in one day....
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Post by the light works on Jan 20, 2017 15:37:41 GMT
It seems like every winter, there's an argument over whether wind chill has any effect on nonliving things -- most commonly, whether sub-zero wind chills are as rough on a car as sub-zero temperatures. Testing this could get tricky, assuming the new show is being filmed in California it would call for either a wind tunnel with refrigeration equipment or a road trip. Hello and welcome to TC. Yes this is worth testing, if only to show people how much it works. -10 outside is still -10 outside, but if its getting colder due to there being a wind coming from a place that is -20 outside, and the wind is therefore -20, then even though its -10, the wind is going to cool it down quickly. The ambient thep of the place you are in and the temp of the wind blowing across it can be that different... and more.... And I suggest a wind tunnel with a chiller on it to blow a cold wind over a static thermometer to see how fast it cooled down with or without the fan running, and at different speeds of fan. Just to put discussion in to others on the board, here in UK, we have North Sea, and Scandinavia to one side, if the wind comes from the north, its the land and seas to that side of the country that dictate the temp of the wind. If from the south or south west, we have gulf stream seas and european continent that "usually" supply warm winds. Wind chill can go to wind warmth and back again, all in one day.... Silver; you are mixing cold wind with wind chill. cold wind is when your air temperature is, for simplicity, 0C, and then a wind of -10 C starts blowing - that will reduce your air temperature to -10. wind chill is when your air temperature is 0C and you have a hard wind of 0C, which makes it feel like it is -10C.
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Post by Cybermortis on Jan 20, 2017 16:58:05 GMT
Off the top of my head Wind Chill applies to evaporation, which increases with wind speed. So while it would apply to humans; and what little investigation I've done seems to indicate that this is what studies have focused on. In theory it shouldn't have any effect on a car.
That said, air with high humidity and low temperature would presumably condense on a warm metal surface and promptly evaporate. This could result in different areas of a vehicle cooling at different rates, placing stress on seals, bolts or welds. This might be especially true of engines, where you also have rubber seals. It also occures to me that this same process could also result in water condensing and freezing in gaps it wouldn't normally do so.
So, actually not a bad idea for the show.
Clearly not something they could do with an entire car; any freezer large enough and accessible for a car is probably not going to let one be parked there. To say nothing about running an engine in an enclosed space. But maybe something that could be done with an engine and radiator? With a hose to carry the fumes outdoors? What parts of a car are said to be affected?
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Post by GTCGreg on Jan 20, 2017 17:25:48 GMT
That said, air with high humidity and low temperature would presumably condense on a warm metal surface and promptly evaporate. It's either going to do one or the other. It can't do both. It's about dew point. If the temperature of the object is below the dew point, you will get condensation. If it's above the dew point you can get evaportion. That is, if the object is already wet. But it wouldn't be wet from condensation.
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Post by the light works on Jan 20, 2017 17:57:25 GMT
Off the top of my head Wind Chill applies to evaporation, which increases with wind speed. So while it would apply to humans; and what little investigation I've done seems to indicate that this is what studies have focused on. In theory it shouldn't have any effect on a car. That said, air with high humidity and low temperature would presumably condense on a warm metal surface and promptly evaporate. This could result in different areas of a vehicle cooling at different rates, placing stress on seals, bolts or welds. This might be especially true of engines, where you also have rubber seals. It also occures to me that this same process could also result in water condensing and freezing in gaps it wouldn't normally do so. So, actually not a bad idea for the show. Clearly not something they could do with an entire car; any freezer large enough and accessible for a car is probably not going to let one be parked there. To say nothing about running an engine in an enclosed space. But maybe something that could be done with an engine and radiator? With a hose to carry the fumes outdoors? What parts of a car are said to be affected? I believe the original show did an episode or two at an automotive proving ground; which has both an oven and a freezer large enough to accommodate a car (or multiple cars) that said, airflow is related to rate of evaporation, but it is more related to increasing heat transfer through increasing contact. as your body is cooled, the air in contact with it is warmed, in still air, that begins to reduce the transfer of heat. wind constantly changes out that air for colder air, which continues the rapid transfer of heat. this principle is used in a internal combustion engine, already. the water pump cycles water through the radiator, which relies on airflow through the radiator to have cool air to transfer the engine heat to. and I agree, this would be workable, with the right testing setup.
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Post by koshka on Jan 20, 2017 19:09:23 GMT
Clearly not something they could do with an entire car; any freezer large enough and accessible for a car is probably not going to let one be parked there. To say nothing about running an engine in an enclosed space. But maybe something that could be done with an engine and radiator? With a hose to carry the fumes outdoors? What parts of a car are said to be affected? I've always been told that the main issue is when you start the engine. Supposedly there's no difference between starting an engine when it's -20 degrees, and starting one when the real temperature is 0 but the wind chill is at -20. Once the engine is warmed up, wind chill doesn't matter; if the web is accurate burning gasoline hits 1700 degrees, and you're not going to hit a low enough wind chill to counter that anywhere on Earth. Theoretically, all you'd need to test that part would be the engine and a heavy-duty fan to provide wind.
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Post by Cybermortis on Jan 20, 2017 19:47:39 GMT
Trouble when starting might be down to the engine oil being thicker at lower temperature. I know that during the winter of 1941/2 German armour was immobilized in Russia by the cold. Which caused the engine oil to turn into something like thick treacle, if not freeze solid. The Germans had to either keep the engine running every hour or so, or in extreme cases build fires under the sump. Starting and engine under those conditions would certainly do it no favours.
I would imagine you might get a similar situation with radiator fluid.
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Post by the light works on Jan 20, 2017 19:58:35 GMT
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Post by GTCGreg on Jan 21, 2017 1:52:50 GMT
With all the artificial intelligence in cars today, maybe we should just ask them if they feel colder in the wind.
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Post by the light works on Jan 21, 2017 2:11:53 GMT
With all the artificial intelligence in cars today, maybe we should just ask them if they feel colder in the wind. well done.
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Post by silverdragon on Jan 21, 2017 8:39:12 GMT
Can all of you look inside your Computer, at the noisy bit, the fan on top of your heatsink over your CPU......
Do I need to say more or is that a perfect example of "Wind chill"?... because that is how the heat transfer from the CPU works?..
This is also how I learnt all about heat transfer during my days in HVAC, moving air moves heat quicker than static air. OK, So most cars [non-american "boat" land-yacht] dont come covered in fins, but a wind will cool the thing, and it also applies to the radiator fan inside the engine bay, or the fan on an air-cooled engine, which you will definitely need to have running when sat idle on a very hot day. Moving air cools a lot faster than static air.
But hell, yeah, its worth a test just to show how much it works.
If anyone has a thermistor and a fan, try this yourself.... [thermistor being an electronic thermometer] Get it nice and warm by putting it against the hot outside of a cup of coffee, then watch the decay in temp when you take it away. Try again, but this time blow on it. If your concerned about the water vapour in your breath, use an electric fan.
However, if its a cold damp wind, your getting colder quicker anyway in the outside world.
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