De-Misting your car......Discuss
#83
#84
#86
tell me this, and tell me no more. if you are standing in a room that is 20 deg. C with a thermometer, will the thermometer read less if you move it around really quickly?
being out of the engine bay is the key.
Last edited by foreigneRS; 14-12-2008 at 07:42 PM.
#87
wind chill only affects people as your sweat is evaporated - it does not affect inaminate objects like temperature sensors i have 13 years of professional temperature measurement experience behind me, how about you 2 clever dicks?
tell me this, and tell me no more. if you are standing in a room that is 20 deg. C with a thermometer, will the thermometer read less if you move it around really quickly?
being out of the engine bay is the key.
tell me this, and tell me no more. if you are standing in a room that is 20 deg. C with a thermometer, will the thermometer read less if you move it around really quickly?
being out of the engine bay is the key.
I cant quite get my head round this though.
Technically speaking, using the example above, if the thermometer is moving fast enough, then the actual thermometer itself will become colder??? (all be it hardly noticeable in this instance )
The actual argument we had in question was say its 20 degress outside, and you stick your arm out the window at say 40mph, then the temperature of your arm will decrease. Most others said it wouldnt and seemed pretty certain, which i just cant get my head round. Of course it will decrease.
So you say it only affects people due to sweat evaporating but if i stuck anything else out the window, then that would reduce the temperature of it surely.
Last edited by S1rst; 14-12-2008 at 09:02 PM.
#89
I dont know mate, thats why im asking. If you stuck it out the window, it would be cooler than it would be if it was just sat there outside yes?
#91
I cant get my head round it. If its 20 degress and my cars been outside all day, so the windscreens say 20 degress, then i fly down the M1 at 100mph, then my windscreen stays at 20 degress.
#92
as for plane wings, do you think that is due to the speed of the plane, or the fact that it's fucking cold up at 20,000 ft?
they are also more complicated as they contain fuel that is part of a system where you have transfer of energy. you need to simplify things down and think of it purely in terms of a lump of wood or something so that you can understand that a simple thermistor used to measure the air temperature on a car bumper cannot be cooled down further than the temperature of the wind on it.
i will say what i said on another thread - why do we need complicated refrigerating systems if all you have to do is blow on your ice cream to stop it melting?
Last edited by foreigneRS; 15-12-2008 at 06:15 AM.
#93
The reason you feel colder when you are moving quickly, is the mass of air being blown over you is conducting heat away from you. Your body is around 37 degrees, so air around you is constantly sucking heat out of you. The air directly around you immediatley heats up so you tend not to feel it so much. Constantly move this air - eg a fan - and you always have cool air around you so you feel it. The actual temperature of the air is unaffected by movement. What you can feel is the rate at which it is conducting heat away from you.
If you walk into your bathroom which has a bath mat on a tiled floor - which feels colder to the touch, mat or tiles? They are infact at exactly the same temperature - both around 20 degrees. Ceramic tile is a very good heat conductor, so sucks the heat straight out of your feet making it feel colder than the bath mat.
If you walk into your bathroom which has a bath mat on a tiled floor - which feels colder to the touch, mat or tiles? They are infact at exactly the same temperature - both around 20 degrees. Ceramic tile is a very good heat conductor, so sucks the heat straight out of your feet making it feel colder than the bath mat.
#94
see, so i'm partially correct eh now stop confusing me with science and sweaty arms out of windows
#95
how can it be anything less? to be a lower temperature, energy needs to have been lost from it. where has that energy gone?
as for plane wings, do you think that is due to the speed of the plane, or the fact that it's fucking cold up at 20,000 ft?
they are also more complicated as they contain fuel that is part of a system where you have transfer of energy. you need to simplify things down and think of it purely in terms of a lump of wood or something so that you can understand that a simple thermistor used to measure the air temperature on a car bumper cannot be cooled down further than the temperature of the wind on it.
i will say what i said on another thread - why do we need complicated refrigerating systems if all you have to do is blow on your ice cream to stop it melting?
as for plane wings, do you think that is due to the speed of the plane, or the fact that it's fucking cold up at 20,000 ft?
they are also more complicated as they contain fuel that is part of a system where you have transfer of energy. you need to simplify things down and think of it purely in terms of a lump of wood or something so that you can understand that a simple thermistor used to measure the air temperature on a car bumper cannot be cooled down further than the temperature of the wind on it.
i will say what i said on another thread - why do we need complicated refrigerating systems if all you have to do is blow on your ice cream to stop it melting?
Anyway, about this lost energy bit, i always thought that heat energy will be lost if its moving (or stuck out a car window for arguments sake). Any heat that the object had stored, would be lost as its being transfered away by the wind/movement. I understand that the molecules around it will actually create a certain amount of heat due to them moving quickly and colliding with each other, but if more heat is dispersed than is created then that should technically cool it down?
Im not doubting what your saying is correct at all mate, as this bit 'refridgeration engineer' sort of gives it away a bit . Its just this heat being lost (or not being lost as it seems to be) by the wind/movement that i cant quite get my head around.
So if its actually the sweat/moisture from our body that is evaporated/transpired by wind/movement that cools us down, then why wouldnt it cool down say an apple that has moisture in it too? Surely it works the same way? Now of course an apple is not at 37.5 degrees but i cant see why it still wouldnt cool down if its stuck out the window.
Last edited by S1rst; 15-12-2008 at 11:16 AM.
#96
I think the Seat Alhambra and VW Sharan people carriers shared some of the same bits as the Ford Galaxy, as they were all built in the same place - heated screen was one of the parts
#97
#99
#101
So if its actually the sweat/moisture from our body that is evaporated/transpired by wind/movement that cools us down, then why wouldnt it cool down say an apple that has moisture in it too? Surely it works the same way? Now of course an apple is not at 37.5 degrees but i cant see why it still wouldnt cool down if its stuck out the window.
but a temperature sensor does not have an endless supply of water in it to evaporate out, hence will be unaffected by windspeed - as per my original point.
in the desert they store their water in a kind of bottle that wicks some of it away over the surface and as that is evaporated by the wind, the bottle of water is kept cool against the desert heat. it's very cunning technology and is basically the principle of the refrigeration system (although it runs out so would not be much cop in your house, hence a closed loop using high and low pressure process is commonly used)
Last edited by foreigneRS; 15-12-2008 at 04:18 PM.
#102
rick has kind of explained it above, but an apple that has water on the outside will be cooled down if the wind evaporates that moisture off.
but a temperature sensor does not have an endless supply of water in it to evaporate out, hence will be unaffected by windspeed - as per my original point.
in the desert they store their water in a kind of bottle that wicks some of it away over the surface and as that is evaporated by the wind, the bottle of water is kept cool against the desert heat. it's very cunning technology and is basically the principle of the refrigeration system (although it runs out so would not be much cop in your house, hence a closed loop using high and low pressure process is commonly used)
but a temperature sensor does not have an endless supply of water in it to evaporate out, hence will be unaffected by windspeed - as per my original point.
in the desert they store their water in a kind of bottle that wicks some of it away over the surface and as that is evaporated by the wind, the bottle of water is kept cool against the desert heat. it's very cunning technology and is basically the principle of the refrigeration system (although it runs out so would not be much cop in your house, hence a closed loop using high and low pressure process is commonly used)
#104
Irritating c........
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From: The Dark Side of the Moon...
The Jap stuff has had "wiper heaters" for years, but untill recently, Ford held the patent for full screen heater elements, which is why you only ever saw them on cars that were part of the Ford Family - Jaguar for example...
All changing now tho....
#105
Irritating c........
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From: The Dark Side of the Moon...
Climate control is a replacement for the common "fan" set up's in cars. Generally goes hand in had with AC (as it conditions the air coming in) and works like a thermostat to control and maintain a steady and constant temperature in the vehicle, with variable fan speed control...
#106
Irritating c........
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From: The Dark Side of the Moon...
come down stairs... boil the kettle, walk outside pour red hot water all over the screen, it gets rid of the frost and ice on the outside and also the steam on the inside, then drive off!!
couldn't ask for a better system
wouldnt reccomend trying it with a crack or big chip in the screen though! could end in disaster...
couldn't ask for a better system
wouldnt reccomend trying it with a crack or big chip in the screen though! could end in disaster...
#107
Irritating c........
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Joined: May 2003
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From: The Dark Side of the Moon...
I'm liking Nick's posts on this thread too - very interesting and also informative.
To "dumb it down" a bit - drive along with you hand out the window. Feels cool/cold right? Your body is radiating heat, and the breeze/wind is transferring this heat away from your skin making it feel colder.
Now pour water over your hand (room temperature if you like, so you can say it wasn't the WATER TEMPERATURE that cooled you down) and carry on driving with your hand out the window. Feels much colder right? Same principal as sweat or condenstation - the breeze/air is working in tandem with the water to expel heat from you. You aren't being made colder as such, but actually having your heat taken away.
Thats how I understand it anyway.... I could be wrong - it's been known to happen
To "dumb it down" a bit - drive along with you hand out the window. Feels cool/cold right? Your body is radiating heat, and the breeze/wind is transferring this heat away from your skin making it feel colder.
Now pour water over your hand (room temperature if you like, so you can say it wasn't the WATER TEMPERATURE that cooled you down) and carry on driving with your hand out the window. Feels much colder right? Same principal as sweat or condenstation - the breeze/air is working in tandem with the water to expel heat from you. You aren't being made colder as such, but actually having your heat taken away.
Thats how I understand it anyway.... I could be wrong - it's been known to happen
#108
#112
you should never let the facts get in the way of a good put down
while we are talking windscreens, who does the screens for esure?
anyone know? the screen has started to de laminate in the corner so would this be done under the windscreen policy or will i have to put water on a stone chip?
while we are talking windscreens, who does the screens for esure?
anyone know? the screen has started to de laminate in the corner so would this be done under the windscreen policy or will i have to put water on a stone chip?
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