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Power cost of idle electric water heater
wrote:
wrote:
|A larger tank should help, given a smaller surface to lose heat from...
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| Larger tanks have less surface?
As the volume goes up proportionally to the cube of a dimension, the surface
area through which heat can escape goes up only proportionally to the square
of a dimension, assuming a constant shape (e.g. ratio between diameter and
length for a cylinder). A tank which doubles in size for all dimensions
will have 4 times the surface area (where the heat escapes), and 8 times the
volume (where heat is held)...
A lovely explanation, but as you write above, larger tanks
have MORE surface, so larger tanks have MORE heat loss...
Larger tanks have LESS increase in surface than the
increase in volume.
Take a 1-foot cube, 1 x 1 x 1. The volume is 1 cubic
foot, and the surface area is 6 square feet. An n x n
x n cube of 2 cubic feet will have n = (approx) 1.26.
The surface area is 6 x 1.25^2 = 9.52 sqare feet. The
volume has doubled, but the surface area has gone up by
LESS than twice.
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