Agree he is not doing expansive cooling.

I beg to differ regarding pipe size
I agree the volume to circumferance is not favorable with larger pipe ie vol goes up by the square of radius change
BUT
the velocity is inversely proportional to the area so what you lose on one hand you gain on the other. With larger pipe size you get slower velocity thus longer contact time
AND more surface area.

He would be much better off by using multi tube heat exchanger water cooled than with single tube but there just may be a cost factor involved which I tried to keep in mind.

dan Bentler