Yes. The friction and motion will degrade to heat. Surely the solution would be to run the water through a loop of pipe (or uninsulated section of the pump body) such that as the heat rises the heat losses would eventually equal the heat gain and no further increase in temperature would result? Which is presumably something the pump manufacturers have achieved if they say their pumps can be run against a closed head?Because all or most of the pump power required at that closed head is converted into heat as the pump efficiency is very low, probably only a few %, if it were (impossibly) still 100% then there would be no heat rise. The efficiencies of very large industrial pumps is often checked/monitored by actually measuring this temperature rise during normal operation.
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No, that's to do with the pressure and volume of a gas. And, yes I did look that up.Physics. Is it Boyles law?