Determining Average Temperature
Date: Summer 2012
I would like to find out what the "average" temperature difference is when the outside temperature is: 85 Fahrenheit, 95, and 100 and 105-what would the inside temperature of an uncovered standard sedan vehicle measure?
There are too many parameters that are unspecified in your problem.
What color is the car? A white car reflects sunlight components whereas a black car absorbs sunlight components.
Is the car parked in direct sunlight or in the shade of a tree or in a garage?
Are the windows open?
Is there an aluminized window shade in the windshield?
I keep a thermometer inside my vehicle, a dark gray Ford Ranger pick up, parked in direct sunshine with an aluminized window shade and the temperature sometimes gets up to 140 degrees Farenheit. You can get a cheap thermometer in an Auto Parts store and place it in your car to answer your specific question.
With regard to the “average”, you have to be careful about what “average” you are talking about. The number average: T(n)= (85+95+100+105)/4 =96.25.
But there are different ways of defining the average. For example suppose the mass of objects are M85, M95,M100,and M105, where none of the masses is the same, then the average might be the weight average, which would be a different number.
As far as the inside temperature of an uncovered standard sedan would be. That is more complicated. For example: What is the air speed, what is the color of the upholstery, is the weather cloudy or clear. There is not a single answer.
It definitely depends upon where you park the car. Much of the heat in a closed car comes from the sun shining in- that's why you see so many folks use sun shades.
Things that would affect the temperature include:
Time parked in the sun, amount of sun (shade, or a gray day,) amount of glass in the car, direction in which the car is parked, window tint, age of car (older cars are not as air-tight as new ones), car type (convertible or sedan) and location in the country (Houston has hotter sun that say Oregon..
Looks like you have a good opportunity to run some experiments.
Otherwise, look up the Humane Society US which has ads against leaving pets in cars. They probably could give you a maximum temperature.
The answer is: in the shade, hot; in the Sun, HOTTER !
Please look up a study performed on car interior temperatures: http://www.mydogiscool.com/x_car_study.php#.T-ylOLXY-So
It is uncertain where your question may lead so let me just add the following:
Automobile interiors become so hot that laws http://www.childwelfare.gov/systemwide/laws_policies/statutes/define.pdf for children; and pets
http://www.animallaw.info/articles/qvuspetsincars.htm are fully exercised in our state.
Speaking as a person: Please do not leave anyone you love confined in a car... ever.
PEHughes, Ph.D. Milford, NH
I do not know the answer to this question, although through experience
it seems that the temperature differential decreases with increasing air
temperature outside the vehicle. Obviously, the wind speed will have an
important effect in removing energy from the vehicle, so an experiment to
determine what the temperature differential is at different air temperatures
would have to include air temperature, wind speed, the length of
time that the vehicle is exposed to the sun, and the intensity of the solar
radiation on the car.
David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory
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Update: November 2011