From: issa@cwis.unomaha.edu (Issa El-Hazin)
Subject: Re: Get a car heated in winter: How long is appropriate?
Keywords: Heating
Organization: University of Nebraska at Omaha
Date: Fri, 8 Jan 1993 01:21:55 GMT

basiji@stein.u.washington.edu (David Basiji) writes:

>issa@cwis.unomaha.edu (Issa El-Hazin) writes:

>>sharen@iscnvx.lmsc.lockheed.com (Sharen A. Rund) writes:

>>>In article <C0G89q.Dox@news.iastate.edu> rdu@iastate.edu (Runqing Du) writes:

>>>warmed up without overheating and freezing up - also, if you can wait till 
>>>11pm to do the job, its a bit better, the coldest part of the evening
>>>hasn't come yet, and, if you don't leave the house till late you may want
>>>to consider running it again in the morning, especially if the temp gets
>>>lowered even more so by the wind chill
>>                             ----------

>>Cars never feel wind chill. Only living things (i.e. people) do.
>>or Am I wrong?


>Anything that's moist from water or other fluids will feel "windchill".
>WC is just additional cooling due to evaporation of the fluid.
>Evaporative refrigerators work on this principle...take a sheetmetal box,
>cover it with canvas, soak the canvas with water, within a couple of hours
>the evaporation of the water will cool the box along with whatever is inside.
>(you also need a reservoir of water dripping onto the canvas to keep it
>from drying out.)

>Cheers,

>David Basiji
>UW Bioengineering
>NeRD #3762


I know what you are talking about (or at least I think). I've took physics,
but I admit it had been 2 years.

To make sure, I've called a physics PhD. this morning here at the Univ. and 
asked him about this. What he said (using my own words) is:
It can be argued both ways, but in general, windchill only effects living 
things. Why then wouldn't a thermostat measure the windchill factor! Like, 
when it's 20F out, but the windchill factor is -50F (with strong winds), the 
thermostat will only read 20F. The strong wind will only make the thermostat 
get to 20F faster (if it just had been taken out of a warm room), due to the 
warm air around it being replaced with colder air at a faster rate.

I didn't ask him, what if this object/thermo was wet for I knew the answer, 
and I agree with you on this one. When I was just a child (may be 6), I
filled a plastic bag with clean water and made very tiny holes near the top, 
covered it with a wet cloth (with a pan underneath, in case of drippage) and 
put it next to my bed in my air conditioned room so I can have cold water if 
I woke up during the middle of the night. I remember the water getting fairly 
cold. I did this only for a couple of nights and, in actuality, only as an 
experimentation. I hope I didn't break any vapor_freezers_copy_righted_laws :).

But in our original topic, the car's engine, how much a wet [on the outside] 
surface have to do with this, and for how long the effect will last? In other 
words, how often an engine after being driven is wet on the outside (little 
steam?) and how long it is before it dries out. Would the effect last thru
the night into the morning hours? I don't know, but I doubt it.

It's time for 70F weather, I'm getting sick of this sub 50F brrrr.

issa