1. NSTX OH Coil Optimization Ali Zolfaghari

2. Optimization Parameters: Coolant channel diameter –Larger coolant diameter will lead to coil temp above 100° C for I=24 kA and tesw=0.8 and above. –Only way to go is down in hole size at the expense of cooling time and advantage of Ohmic driven pulse length. Manifold Pressure –Higher pressure leads to higher mass flow and shorter cooling time. –Need to understand the actual pressure drop driving the flow in the coil considering losses elsewhere in the flow path.

3. Establishing the simulation accuracy Using experimental water temp data for a shot with existing coil. Current=24 kA T-esw=0.311 s Length=107 m Flow = 0.67 GPM 400 PSI pump

4. Establishing the simulation accuracy

5. The difference between measured and simulated peak temperature results is attributed to the fact that Fcool does not treat the complete transient heating of the copper and the simultaneous cooling by the entrained water during the heating pulse. CFD is better suited to resolve the transient detail of the heating pulse. To predict the overall cooling time, Fcool is accurate and its cooling time values agree with CFD results. Fcool is much faster to run!!.

6. CSU Conductor Geometry with 0.175 in. Dia. Hole Based on preliminary calculations on temp rise decided to go down to 0.175 in. diameter hole (from 0.188 in.). Goal is to take a tesw of 0.85 sec. (I=24 kA) in the CSU conductor without exceeding 100 deg C. CFX was used to resolve the initial temp rise dynamic up to the plateau. Fcool was used to predict cooling time vs. pressure drop for the 0.175 in hole diameter and 217m conductor length.

7. Heating energy spread evenly from 0-7 seconds I2t = 4.9e8 a2s 100 deg C CFX Results CSU Conductor Geometry with 0.175 in. Dia. Hole

8. Heating energy in two steps for 0-1.2 sec. and 1.2-6.8 sec. I2t = 4.9e8 a2s 96 deg C CFX Results CSU Conductor Geometry with 0.175 in. Dia. Hole

9. 400 PSI Pump gives 25 min. cooling time

10. 500 PSI Pump gives 21.5 min. cooling time

11. 600 PSI Pump gives 19 min. cooling time