Keeping Emmy Cool - White Paper (STULZ Modular, University of Gottingen hybrid liquid/air cooled HPC data centre)
STULZ · Christian Boehme, Sebastian Krey et al.
A case study of the modular data centre built for the 'Emmy' supercomputer at the University of Gottingen. It gives design temperatures, the per-rack liquid/air heat split and the measured PUE results.
On this page
Overview
The facility has a 70 m2 air-cooled room and an 85 m2 direct liquid-cooled (DLC) room, about 1.4 MW in total. The DLC systems total 1,120 kW, with 11 racks installed at 96 kW and space for 14. Most server heat is taken directly from the chip into liquid, and the remainder is handled by precision air cooling and row coolers.
The per-rack split is explicit: of a 96 kW rack, DLC removes 74.9 kW (78 %) and air handles 21.1 kW (22 %). Chip return water reaches about 55 C, supply air runs at 27-35 C and water at 32-36 C. ASHRAE class H1 high-density equipment requires an inlet of 22 C or less.
Cooling relies on dry-cooler free cooling, with 35 % ethylene glycol in the primary loop as antifreeze. Free cooling saves about 40 % and the glycol economiser up to 55 %. Design PUE is 1.14 at 75 % peak load with 32 C ambient and at 100 % load up to 19 C ambient. The measured annual facility PUE is 1.13 against a target below 1.14, with a quoted 1.07 for the liquid-cooled part.
Key points
- Measured annual facility PUE 1.13 against a target below 1.14 (1.07 quoted for the liquid-cooled part).
- 70 m2 air-cooled room plus 85 m2 DLC room, about 1.4 MW total; 1,120 kW of DLC systems.
- 11 racks installed at 96 kW, space for 14.
- Per rack, DLC removes 74.9 kW (78 %) and air 21.1 kW (22 %).
- Design PUE 1.14 at 75 % peak load at 32 C ambient and 100 % load up to 19 C ambient.
- Chip return water up to about 55 C; supply air 27-35 C; water 32-36 C.
- 35 % ethylene glycol in the primary loop; free cooling saves about 40 %, the glycol economiser up to 55 %.
- ASHRAE H1 high-density equipment requires inlet at or below 22 C.
Using it in design
- Model the per-rack heat split (liquid %/air %); it drives both CDU and CRAH sizing.
- Use the Emmy figures (96 kW, 78/22) as a validation fixture.
- If equipment is ASHRAE H1, cap the supply-air inlet at 22 C and warn on higher setpoints.
- Give primary loops a glycol fraction field, since it affects cp and pump energy.
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Who should read it
Engineers designing hybrid liquid/air cooled HPC and AI halls.
Related standards
- ASHRAE TC 9.9 (H1 class)
- EN 50600
Publication details
- Authors
- Christian Boehme; Sebastian Krey; Dave Meadows; Norbert Wenk
- Publisher
- STULZ
- Year
- 2024
- Document language
- English
- Source type
- Manufacturer
- Access
- Free to read
- Licence
- Copyright retained; citation only — the publisher’s terms apply to the original document
Citation
Christian Boehme; Sebastian Krey; Dave Meadows; Norbert Wenk (2024). Keeping Emmy Cool - White Paper (STULZ Modular, University of Gottingen hybrid liquid/air cooled HPC data centre). STULZ. https://www.stulz.com/fileadmin/user_upload/Documents/Downloads/Whitepaper/KEEPING_EMMY_COOL_WHITE_PAPER_STULZ_MODULAR.pdf
Events on this subject
- ISK-SODEX Istanbul 2027
- SC26 – International Conference for High Performance Computing, Networking, Storage and Analysis
- Data Center World Middle East
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