Newton's Law of Cooling may be written as
T(t) =S + (T0 - S)e -kt, where k is a constant that depends on the shape of the object, wind speed, etc., T0 is initial temperature of the object at time =0, S is constant temperature of the surroundings, and T(t) is the temperature of the object after t minutes.
Excel has no trendline model to fit this. But Solver can do a fine job. If you are interested I can send you a file showing how. Reply to my private email address (not the group)
best wishes
--
Bernard V Liengme
www.stfx.ca/people/bliengme
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"Mike Milligan" wrote in message ...
I am looking for an exponential falloff trendline tool. I have a chart that
is plotting temperature data of a part that is cooling down (or heating up)
and will eventually arrive at a stable temperature. I'd like to use a
trendline to predict that stable temperature. Anyone have one, or know how
to use Excel built-in to the same end?

Mike