Title: Thermal Hydraulics of Helium-Cooled Finger-Type Divertors at Higher Incident Heat Fluxes

Abstract

Over the last decade, a number of studies at the Georgia Institute of Technology (GT) have evaluated the thermal hydraulics of the design of the helium-cooled modular divertor with multiple jets (HEMJ) originally developed at the Karlsruhe Institute of Technology. Using the GT helium loop, a test section of a single HEMJ finger heated by a radio-frequency (rf) induction heater was studied at near prototypical condition at pressures of ~10 MPa, maximum mass flow rates of 8 g/s, and maximum helium inlet temperatures Ti of 425°C. The area-averaged cooled surface temperature was estimated from embedded thermocouple measurements. This, together with the average incident heat flux ${\bar{q}}^{\prime \prime }$, was used to determine the average heat transfer coefficient and the corresponding Nusselt number $\overline{Nu}$ over the cooled surface. The normalized pressure loss coefficient KL was determined from the pressure drop measured across the test section. The helium loop was modified last year by enclosing the test section and heater within an argon-filled stainless steel chamber to minimize oxidation of the tungsten-alloy test section. Initial results, when extrapolated to prototypical conditions, suggested that $\overline{Nu}$ was about 20% higher than our previous results. However, the maximum heat flux for these results was less than 3 MW/m2 due to rf coupling with the steel chamber walls. The chamber was then recently upgraded to a glass–stainless steel enclosure with modified feedthroughs for the induction heater connections to minimize this coupling. With this upgrade, a maximum incident heat flux ${\bar{q}}^{\prime \prime }$ = 8.1 MW/m² was achieved. This work presents experimental estimates and correlations for $\overline{Nu}$ and K_L at higher heat fluxes. These results provide greater confidence when estimating the maximum heat flux that can be accommodated by the HEMJ at fully prototypical conditions. Lastly, preliminary metrology results for the test section used to experimentally study the simplified flat design variant of the HEMJ are presented as part of an effort to resolve recently reported discrepancies between experimentally estimated and numerically simulated $\overline{Nu}.$

Authors:

Lee, D. S.  ^[1];

• Search DOE PAGES for author "Lee, D. S."
• Search DOE PAGES for ORCID "0000-0001-5709-7665"

Musa, S. A.  ^[1];

• Search DOE PAGES for author "Musa, S. A."
• Search DOE PAGES for ORCID "0000-0002-4311-3334"

Abdel-Khalik, S. I. ^[1]; Yoda, M.  ^[1]

• Search DOE PAGES for author "Yoda, M."
• Search DOE PAGES for ORCID "0000-0003-2518-8911"

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+ Show Author Affiliations

1. Georgia Inst. of Technology, Atlanta, GA (United States). G. W. Woodruff School of Mechanical Engineering

Publication Date:

Thu May 02 00:00:00 EDT 2019

Research Org.:

Georgia Institute of Technology, Atlanta, GA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Fusion Energy Sciences (FES)

OSTI Identifier:

1593394

Grant/Contract Number:  

FG02-01ER54656

Resource Type:

Accepted Manuscript

Journal Name:

Fusion Science and Technology

Additional Journal Information:

Journal Volume: 75; Journal Issue: 8; Journal ID: ISSN 1536-1055

Publisher:

American Nuclear Society

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Helium-cooled divertors; thermal hydraulics; modular divertor with multiple jets; impinging jets