[sbaiddn]

His understanding appears worse than that. Heat capacity is important, but as a second order. Absolute temperatures is the real deal since it sets the Carnot efficiency.

Another way to look at it, if I were doing a back of the envelop calculation (the most important calculations), I wouldn't look up the Cp of Na. Id only look up its boiling T

High Cp, low Cp... that can be remedied to some extent by running the pump faster or slower.