[Carry_Okie]

I don't understand that thought. A mass of material is going to require the delivery of the same amount of BTU's to raise it to a set temperature, regardless of the velocity it moves through the system.

The thought was that higher pressures would mean more material in a given volume. That means a smaller vessel. That reduces the surface-to-volume ratio for heat transfer and also means a shorter mean free path for the molecules to acquire that heat. So premise was related to efficiency of heat transfer, not the amount of heat a particular mass of material would require. I asked that question because of the risk associated with higher operating pressures at those temperatures.

[thackney]

Okay, I understand why you took it that way.

Material would have to get exotic/expensive if you try to maintain 1,000°F at 1,000 psi.