weather report

[low_delta]

The temps were above zero, this morning. The winds aren't as strong as yesterday. Still no snow.

I checked the wind chill with one of those online calculators yesterday morning. -4°F and 18 mph wind = -46°.

Comments

[vlinker.livejournal.com]

well, your car will start as if it were -4°F and no wind.......

[low-delta.livejournal.com]

People say that wind chill affects batteries, but I don't believe them.

Re:

[vlinker.livejournal.com]

wind chill affects "human flesh".......

that's in the definition......

of course, the wind does increase the surface heat transfer coefficient and will help remove heat from anything quicker than without wind......but, once an item is at ambient temperature, no amount of wind will remove additional heat from it.....

heat transfer

[emschin.livejournal.com]

I'm asking you this question because anyone who uses words like "surface heat transfer coefficient" and lives in Alaska sounds like they know what they're talking about. :^)

When you're taking a car out of an unheated garage and driving it in -4 degree weather about 20 minutes, how cold do you think the outside of the car AND the engine would be? (I assume that running the engine creates warmth enough to counteract some air temp.) Does it ever get down to -4?)

If it's not that cold and you park it facing the wind on the outer row of a parking structure, would it get colder faster than if you parked it in the inner part where it's sheltered from the wind? (Down to the temp of the ambient air.)

Re: heat transfer

[vlinker.livejournal.com]

LOL.....thanks loads....

i can simplify this question a bit to make it easy to answer......and to do that, i assume that the unheated garage is an unattached unheated garage, so that there is no heat input to the garage from a house......additionally, i'll assume that there is no radiation heat input from the sun (like if the place had a nice black roof)......so, indeed, the interior of the garage is at -4°F.....so, just before the car starts, everything is at a nice -4.......after 20 minutes of driving the car will be somewhat warmer.......hopefully, the engine coolant will be to operating temp, 180, 190, 205.....whatever, the thermostat is set at.....and of course, the occupant will have the heater on, which pulls heat from the cooling system and warms air that's blown into the interior of the vehicle......so, the temperature of the outside of the passenger compartment of the vehicle will be between -4 and the interior temp.....prolly closer to -4 if you're speeding.....hahaha.......the temperature of the tip of the tailfin on the caddy will be sooooo close to -4 that you won't be able to measure the difference with most sensitive instruments.....so, theroretically, once you start putting heat in, everything gets warmer...a little bit......

and of course, when you park it in a sheltered spot, it will cool of more slowly than if in a windy spot......it's just HS physics....

once we add radiation heat transfer, we can see how a surface temperature can actually be BELOW air temperature......

[serendipity.livejournal.com]

The last winter I spent in the Midwest saw temperatures of -50 degrees with wind chill. Right up to the day before we got the hell out of there. I remember it all too painfully well.

[low-delta.livejournal.com]

I've seen worse.