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Re: Keeping coffee hot...



The coffee question turns on the rate of cooling of the hot cup. The
convective cooling rate of an object in a moving fluid increases with
increasing temperature difference between the object (in this case
the coffee and the cup) and the cooling fluid (the air). In the case
of passive convection the air is motivated by this difference. Its
buoyancy and, consequently, its speed inceases as the temperature
difference increases. Since the rate of cooling is intended to be
minimized, and since the cream must ultimately be added anyway, the
best time to add it is immediately, bringing the temperature of the
cup and coffee, and hence the cooling rate, down sooner.

Leigh