Richard Tanzer wrote:

Dan wrote in :

Richard Tanzer wrote:

One seasonal advantage of a submerged pump, relative to a pump that
sits outside the pond, is that all the electrical energy that goes
into the pump is dissipated as heat into the water. So in the
winter, if your pump is drawing 100 watts of power, you are adding
100 watts of heat to the pond.

Actually, that would only be true if you had the world's most
inefficient pump, i.e., one that moved no water. A certain
amount of energy is 'wasted' as heat, but hopefully only a
small fraction of that consumed by the pump.


Dan, I believe you are mistaken. Even if I had the world's most
efficient pump, all the energy that goes into moving the water around is
lost to friction, i.e. drag forces. Otherwise the water would keep
accelerating as you continued to add energy.

Yes, the only difference is that the heat from the more efficient pump is
distributed more evenly around the pond, while the heat from the
inefficient pump tends to be conducted directly from the pump. The
inefficient pump will more quickly melt a hole in the ice :-)
--
derek