Wayne,

With respect to the NCSX Helium Bakeout / Cooling System

….The interlock for the Helium Blower on the NSTX System is set at 28 psi differential.  This setting is determined by the maximum allowable dP across the blower seal which is about as high as I could find for a positive displacement blower.  Paul’s calculation assumes a 28psi pressure drop is available to the vessel tubing.  In reality the available pressure drop for a system with a positive displacement blower will be 28 psi minus the other system losses. Using the NSTX calculations as guidance we can assume we are able to limit the losses in the system exclusive of the vessel tubing to about 7 psi if we are careful in sizing the equipment and piping.  This means we must also be careful about sizing the manifolds which connect the tubing (is this already well defined?).  I calculate that we may use about 7 psi of the pressure drop budget through the heat exchangers, heater, and piping leaving 21 psi of the available 1.9 atm (28 psi) pressure drop to cool NCSX.  I calculate that this would degrade the cooling as calculated by Paul by about 13%.  This means that it is likely that for the heat input of 14.4 MJ the vessel temperature will ratchet up above 48C by a few degrees.  This is all back of the envelope calculations but at first glance I would say if we can accept a slightly higher vessel temperature for the cooling requirement we should be ok.

The Heating parameters in Paul’s calculations shouldn’t be too hard to achieve.

Mike