The kinetic energy in the system in fairly constant, the pump spins at a constant rpm and the fluid flows at a constant rate.
the pump isn't try to spin any faster than it already is. thus, once a fluid is in motion and you are not accelerating it, no extra energy is being added to the system.
seriously 99% of the heat from the pump is from contact, but that heat is only a fraction of energy the pump consumed.
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