[AT] Carburetor Icing (Off Topic)

[Larry D Goss]

Wind chill has to do with the psychology of how air temperature feels.  It 
has nothing to do with actual temperature.  The Siple-Passel equation is 
"not exactly" good scientific work.  That may be one of the reasons why the 
weather service latched on to the concept of wind chill -- it plays into the 
hands of weather reporters whose basic philosophy is to pump anxiety about 
the weather into the listening and watching public.

The old technique (dating from 1909) made use of a wet bulb-dry bulb 
thermometer.  From a comparison of the two temperature readings, the 
relative humidity of the air could be determined by using a nomograph 
(chart).  The easy way to draw that chart was to make it as a triangle. 
Sixty years ago a triangular sling psychrometer was a common instrument for 
heating and air-conditioning contractors to use in determining the comfort 
index.  You swung the instrument around your head on a string for a few 
seconds, read the two temperatures, and projected the readings directly over 
to the appropriate space on the chart to get the relative humidity ( an 
accurate process) and the comfort index.  The comfort index depended on the 
subjective evaluations of what temperature-humidity combinations felt good. 
That's the problem that still exists when using the comfort index, heat 
index, or wind chill.  All three of them are subjective and have nothing to 
do with any directly measurable temperature.  Nowadays, psychrometers are 
digital and/or have a small handle attached to them rather than the long 
string or leather thong that they used to have.

This is more than you wanted to read about any of this.

Larry

----- Original Message ----- 
From: <JTakemoto at wildblue.net>
To: "Antique tractor email discussion group" <at at lists.antique-tractor.com>
Sent: Sunday, December 09, 2007 12:42 PM
Subject: Re: [AT] Carburetor Icing (Off Topic)


>I can see why this subject is so confusing after looking up wind chill I
> found this.
>
> 1.  According to the new NWS Wind Chill Chart, if the temperature is 0
> degrees Fahrenheit and the wind is blowing at 15 mph, the wind chill is
> -19 degrees Fahrenheit. This means that without any wind (actually a 3 mph
> wind or a 3 mph walking rate), the rate of heat loss would equal that of
> outside air at -19 degrees Fahrenheit. At this wind chill temperature,
> exposed skin can freeze in 30 minutes. For other conditions of wind and
> temperature, check out the new NWS Wind Chill Chart and Calculator.
>
> So much for the chilling effects of wind and cold temperatures on human
> skin. What about the effect of wind chill on things like car radiators or
> exposed water pipes?
>
> 2.  Because wind chill is based on removing heat from the human body,
> there is no wind chill for inanimate objects, such as car radiators and
> water pipes. However, there is a faster heat loss with increasing winds,
> so the amount of time for an object to cool to the actual air temperature
> is less. Regardless, the inanimate object cannot not cool below the actual
> air temperature. Thus, if the temperature outside is -5 degrees Fahrenheit
> and the wind chill temperature is -31 degrees Fahrenheit, then your car's
> radiator will not drop lower than -5 degrees Fahrenheit.
>
> Now if that isn't confusing then I sure don't know what it.
>
> According to this a Human body can freeze in 40 degree weather but a car
> radiator can't do the same thing by having  wind blowing across the body.
> Now i ask what is the difference between a radiator and your body when it
> comes to  wind blowing across it.
> According to this I guess it won't freeze a dead body only a live one.
>
> Well I give up let the expert figure it out.
> J.
>
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