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Proving DRACO will deliver
The United States is now closer than it has been in over five decades to launching the first nuclear thermal rocket into space, thanks to DRACO—the Demonstration Rocket for Agile Cislunar Orbit.
B. Zhao, S. A. Musa, S. I. Abdel-Khalik, M. Yoda
Fusion Science and Technology | Volume 72 | Number 3 | October 2017 | Pages 294-299
Technical Paper | doi.org/10.1080/15361055.2017.1333827
Articles are hosted by Taylor and Francis Online.
The helium-cooled modular divertor with multiple jets (HEMJ) can potentially accommodate the large steady-state heat fluxes expected in future long-pulse magnetic fusion reactors. This work, which is part of the joint US-Japan PHENIX collaboration, describes recent results on a single HEMJ “finger” unit obtained in a helium loop operating at prototypical pressures of ~10 MPa. A new heater was used to increase the maximum coolant inlet temperature ≤ 400°C (vs. the prototypical value of 600°C) at incident heat fluxes ≤ 4.5 MW/m2 at these elevated temperatures. The effect of varying the jet-to-impingement surface separation distance H from 0.47 mm to 1.49 mm was also studied for mass flow rates ≤ 8 g/s. Numerical simulations of this HEMJ test section were also performed to obtain local information that could not be measured in the experiments.
Varying H within this range appears to have little effect on both the dimensionless heat transfer coefficient, or Nusselt number , and the dimensionless pressure drop across the HEMJ, or loss coefficient . The experimental measurements do, however, give lower after re-calibration of the differential pressure transducer; these results are now in better agreement with numerical predictions compared with previous experimental data. The experimental results obtained at higher and for are, however, lower than those predicted by a correlation for obtained from extensive measurements taken at lower temperatures in the same facility. These initial results require further examination because they are contradicted by the numerical predictions. If these results are valid, they suggest that the maximum heat flux that can be accommodated by a divertor module may be lower than expected.