Freezable de icer????
19 February 2003, 01:18 PM
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The last 2 mornings now, I have had to de ice my windows with Holts de icer. After spraying it on and leaving it for a while, started to drive off, and the screens froze again. Should this be happening at -4 degrees?
19 February 2003, 08:31 PM
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When moving the temperature will still be -4 regardless of how fast you are driving. So nowt really to do with wind chill.
More likely is that the solvent in the de icer, usually something like alcohol evaporates leaving the left over water to freeze at it's freezing point of 0 degress C.
Basically, if you use de icer you should still clear the liquid off the glass before pulling away.
Cheers
Ian
[Edited by IWatkins - 2/19/2003 8:37:30 PM]
More likely is that the solvent in the de icer, usually something like alcohol evaporates leaving the left over water to freeze at it's freezing point of 0 degress C.
Basically, if you use de icer you should still clear the liquid off the glass before pulling away.
Cheers
Ian
[Edited by IWatkins - 2/19/2003 8:37:30 PM]
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19 February 2003, 09:40 PM
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Well actually what can happen is you set off with the windscreen squirters working, then once you're on the move the squirters stop working. Although the temperature doesn't drop, this is due to 'wind chill'.
The squirters are wet. Airflow over them causes the moisture to evaporate quicker, cooling the nozzles so they gum up
The squirters are wet. Airflow over them causes the moisture to evaporate quicker, cooling the nozzles so they gum up
19 February 2003, 10:35 PM
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I may be wrong, but i am sure that i read somewhere that although de-icer causes ice to melt - it actually reduces the temperature even further (due to to the state change). However, the de-icer/water mix has a lower freezing point than plain water - which is why it initially remains liquid.
If you don't clear this mix of the screen whilst it is liquid, when the de-icer evaporates, the remaining water (which is extra-cold, and on a similarly extra-cold windscreen) will quite obviously freeze again (even harder).
mb
If you don't clear this mix of the screen whilst it is liquid, when the de-icer evaporates, the remaining water (which is extra-cold, and on a similarly extra-cold windscreen) will quite obviously freeze again (even harder).
mb
20 February 2003, 06:19 AM
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lol- how does traveling through air cause it to drop in temp!
Try reading up on windchill courtesy of NASA:
http://pumas.jpl.nasa.gov/examples/l..._Id=10_31_01_2
Simon.
20 February 2003, 06:28 AM
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Well actually what can happen is you set off with the windscreen squirters working, then once you're on the move the squirters stop working. Although the temperature doesn't drop, this is due to 'wind chill'.
20 February 2003, 07:09 AM
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So answer me this. Example. If I put a tray of water that just covers the surface outside now, it would not freeze as quickly as when the water is on my car windscreen. So how do you explain this?
20 February 2003, 07:16 AM
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I don't know, maybe the fact that water on your windscreen is a very thin layer? Or the fact that warm water freezes quicker than cold (it does) and your windscreen is slightly warmer?
It can't be wind chill as such though.
It can't be wind chill as such though.
20 February 2003, 09:32 AM
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From How Stuff Works:
[Edited by NotoriousREV - 2/20/2003 9:33:37 AM]
You have probably heard weatherpeople on the TV news talking about the windchill factor. The windchill factor is the temperature that a person feels because of the wind. For example, if a thermometer reads 35 degrees Fahrenheit outside and the wind is blowing at 25 miles per hour (mph), the windchill factor causes it to feel like it is 8 degrees F. In other words, your 98-degree body loses heat as though it is 8 degrees outside.
The windchill factor is the same effect that causes you to blow on hot soup to cool it down. The movement of the air increases the soup's loss of heat by convection, so the soup cools down faster. See How Thermoses Work for details on radiation, conduction and convection.
For an inanimate object, windchill has an effect if the object is warm. For example, say that you fill two glasses with the same amount of 100-degree water. You put one glass in your refrigerator, which is at 35 degrees, and one outside, where it is 35 degrees and the wind is blowing at 25 mph (so the windchill makes it feel like 8 degrees). The glass outside will get cold quicker than the glass in the refrigerator because of the wind. However, the glass outside will not get colder than 35 degrees -- the air is 35 degrees whether it is moving or not. That is why the thermometer reads 35 degrees even though it feels like 8 degrees.
The windchill factor is the same effect that causes you to blow on hot soup to cool it down. The movement of the air increases the soup's loss of heat by convection, so the soup cools down faster. See How Thermoses Work for details on radiation, conduction and convection.
For an inanimate object, windchill has an effect if the object is warm. For example, say that you fill two glasses with the same amount of 100-degree water. You put one glass in your refrigerator, which is at 35 degrees, and one outside, where it is 35 degrees and the wind is blowing at 25 mph (so the windchill makes it feel like 8 degrees). The glass outside will get cold quicker than the glass in the refrigerator because of the wind. However, the glass outside will not get colder than 35 degrees -- the air is 35 degrees whether it is moving or not. That is why the thermometer reads 35 degrees even though it feels like 8 degrees.
20 February 2003, 11:49 AM
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NotoriousRev, thanks for proving my point 
Windchill is nothing other than the feeling of coldness. It is radiation, convection etc that causes objects, other than ourselves, to cool.
Edited to say what if, on a sunny spring day the temperature is 20c and I'm cruising along at 100mph (in Germany obv). If I washed my windscreen surely if 'windchill' cools water then in the above scenario it would freeze?
[Edited by MooseRacer - 2/20/2003 12:06:43 PM]
Windchill is nothing other than the feeling of coldness. It is radiation, convection etc that causes objects, other than ourselves, to cool.
Edited to say what if, on a sunny spring day the temperature is 20c and I'm cruising along at 100mph (in Germany obv). If I washed my windscreen surely if 'windchill' cools water then in the above scenario it would freeze?
[Edited by MooseRacer - 2/20/2003 12:06:43 PM]
20 February 2003, 12:02 PM
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The glass outside will get cold quicker than the glass in the refrigerator because of the wind. However, the glass outside will not get colder than 35 degrees -- the air is 35 degrees whether it is moving or not. That is why the thermometer reads 35 degrees even though it feels like 8 degrees.
20 February 2003, 01:30 PM
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Web bulb and dry bulb. Don't get me started
Dry bulb temperature (in a meteorological sense) is the temperature of air using a thermometer that isn't being affected direct or indirect solar radiation. I.e. it is sheilded from external radiation inputs. With this is doesn't matter if the wind blowing past it is at 5mph or 200mph, it'll still read the same temperature.
Wet bulb temperature is the temperature (Tw) at which pure water must be evaporated into a given sample of air, adiabaticaly and at a constant pressure, in order to saturate the air at temperature Tw under steady-state conditions. I.e. it is a temperature that is lower than the dry bulb caused by the cooling affect of water evaporating off it. This is why when you are in dense fog (humidity 100% = air is saturdated), the wet bulb and dry bulb temperatures are equal.
Does that help ?
In addition, cooling of windscreens overnight in freezing conditions and their apparant cooling due to wind while driving in freezing conditions is also affected greatly by its radiative properties. I would suggest that the reason screen wash etc. can freeze on the windscreen when you are driving (if air temp is low enough) is caused by the forced evaporation of the water off the screen rather than it being cooled due to wind chill.
Cheers
Ian
Dry bulb temperature (in a meteorological sense) is the temperature of air using a thermometer that isn't being affected direct or indirect solar radiation. I.e. it is sheilded from external radiation inputs. With this is doesn't matter if the wind blowing past it is at 5mph or 200mph, it'll still read the same temperature.
Wet bulb temperature is the temperature (Tw) at which pure water must be evaporated into a given sample of air, adiabaticaly and at a constant pressure, in order to saturate the air at temperature Tw under steady-state conditions. I.e. it is a temperature that is lower than the dry bulb caused by the cooling affect of water evaporating off it. This is why when you are in dense fog (humidity 100% = air is saturdated), the wet bulb and dry bulb temperatures are equal.
Does that help ?
In addition, cooling of windscreens overnight in freezing conditions and their apparant cooling due to wind while driving in freezing conditions is also affected greatly by its radiative properties. I would suggest that the reason screen wash etc. can freeze on the windscreen when you are driving (if air temp is low enough) is caused by the forced evaporation of the water off the screen rather than it being cooled due to wind chill.
Cheers
Ian
20 February 2003, 01:47 PM
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Is that your garage????
That looks excellent.
I have a garage, but as we have just moved in, it's still full of boxes. Might have to look at re designing it like yours. I used the left over carpet they put down to cover most of the garage, but I don't think the light cream will stay that way long
That looks excellent.
I have a garage, but as we have just moved in, it's still full of boxes. Might have to look at re designing it like yours. I used the left over carpet they put down to cover most of the garage, but I don't think the light cream will stay that way long
20 February 2003, 02:06 PM
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I think we're all agreed, aren't we? You said "it's not wind chill" and I said "it's down to evaporation" (which I called wind chill). So it's not wind chill, but it is the effect I described 
20 February 2003, 02:51 PM
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Carl,
Basically, yes. Wind chill is the increased rate of convection/radiation/condution of heat from a body that is warmer than its surroundings due to wind.
Evaporative cooling is the lowering in temperature of an object due the evaporation of a liquid from its surface.
The two are not the same.
Cheers
Ian
Basically, yes. Wind chill is the increased rate of convection/radiation/condution of heat from a body that is warmer than its surroundings due to wind.
Evaporative cooling is the lowering in temperature of an object due the evaporation of a liquid from its surface.
The two are not the same.
Cheers
Ian
20 February 2003, 03:30 PM
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De-iceing Scooby-babe style(my other half)
She fills a 2litre plastic lemonade bottle up with hot water,and places it on the dashboard(over the blower vents).She then starts the car and puts the blower on full,also the rear heated screen goes on.
She then locks the car with the spare key.
She then gives me a shout to let me know the bacon butties are ready.
I mess around in the bathroom for 5mins,get dressed,collect the spare key and bacon butties,and drive to work in a fully de=frosted warmish car.
Dont see what all the fuss is about........
Later Yoza
She fills a 2litre plastic lemonade bottle up with hot water,and places it on the dashboard(over the blower vents).She then starts the car and puts the blower on full,also the rear heated screen goes on.
She then locks the car with the spare key.
She then gives me a shout to let me know the bacon butties are ready.
I mess around in the bathroom for 5mins,get dressed,collect the spare key and bacon butties,and drive to work in a fully de=frosted warmish car.
Dont see what all the fuss is about........
Later Yoza
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