Improving Rack Cooling Performance Using Airflow Management(TM) Blanking Panels

Overview

The laboratory test used thirty 1U server simulators at 150 W each (4.5 kW) in a 42U enclosure with an 11U gap. With blanking panels the hottest server's inlet dropped from 35 C (95 F) to 23 C (73 F), a 12 C (22 F) reduction, while bottom servers stayed unaffected at 21 C (70 F). Field measurements in rooms with mixed density and short rows showed inlet reductions from 2.8 to 8.3 C (5 to 15 F).

Without eliminating recirculation, the only remedy is lowering the bulk supply temperature, which reduces air-conditioner efficiency and increases condensate and humidification needs. With blanking panels the same server inlet temperature is achieved at a higher air-conditioner discharge temperature, which reduces dehumidification and raises efficiency.

The paper discusses why panels are often omitted (misunderstanding, and the effort of screw-in panels) and compares tool-less 1U snap-in panels with screw-in kits for 100 racks with 10U empty each (1000U): snap-in panels save 41.2% of material and 96.7% of labour cost and install about 30 times faster.

A checklist covers other in-rack recirculation paths: blank all unused U; do not use 23 in (584 mm) racks with rails set to 19 in (483 mm); use brush or shield panels for cable pass-through; use fully perforated front and rear doors (no glass); bay racks together.

Key points

1. Test: 42U enclosure with an 11U gap, thirty 1U simulators at 150 W each (4.5 kW).
2. Blanking panels cut the hottest server inlet from 35 C to 23 C (12 C / 22 F); bottom servers stayed at 21 C.
3. Field inlet reductions were 2.8-8.3 C (5-15 F).
4. Without stopping recirculation the only fix is a lower supply temperature, which cuts efficiency and raises condensate and humidification needs.
5. For 100 racks with 10U empty each (1000U), snap-in 1U panels save 41.2% material and 96.7% labour and install about 30 times faster.
6. Checklist: blank all unused U; no 23 in racks with 19 in rails; brush/shield panels at cable pass-throughs; fully perforated doors; bay racks together.
7. With panels the same inlet temperature is reached at a higher discharge temperature, reducing dehumidification.

Using it in design

• Add rack catalogue fields for door perforation percentage (warn on glass or below the full-perforation spec), rail width versus cabinet width (warn on a 23 in cabinet with 19 in rails and no side seals) and blanking included.
• In the rack elevation editor compute empty U per rack, add 1U blanking panels to the BOM automatically, and warn when open U sits above or below powered equipment.
• Flag gaps between adjacent racks in a row (bay them together or add gap fillers).
• When blanking is not specified, assume up to a 12 C inlet penalty for equipment above open gaps.

Who should read it

Designers and operations teams managing in-rack airflow.

Publication details

Authors

Neil Rasmussen

Publisher

Schneider Electric

Year

2011

Document number

WP 44

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