Simulation Test on Cooling and Fire Suppression with Liquid Nitrogen in Computer Room of Data Center

Overview

The paper notes that Chinese computer-room design rules allow gaseous agents (HFC-227ea, IG541, aerosol) and water-based systems (pre-action, high-pressure fine water mist), and argues that gaseous agents are costly and water damages equipment, so it examines liquid nitrogen as an alternative. The rig is a 1 m acrylic cube containing six 25 cm × 25 cm × 35 cm boxes representing computers, scaled from full size with Froude scaling (Q_M/Q_F = (l_M/l_F)^(5/2)), with heaters, oxygen sensors and thermocouples.

Seven fan-shaped and solid-cone nozzles were compared, then optical-fibre and UPS-component fires were extinguished. The authors state the injected liquid nitrogen must occupy more than 33% of the fire-site space; because electronics tolerate low temperature differently, injected mass was limited to less than 0.65 kg, from an initial room temperature of about 20 °C. With the 6520# nozzle the minimum container-side temperature fell to about 10 °C within 300 s, against about 12 °C within 600 s for 6510# and 16 °C for 6530#. Solid-cone nozzles were prone to frosting and blocking.

With the best nozzle, relative temperature changed by more than 50% within 5 min and oxygen concentration in the test space dropped below 10%. Liquid nitrogen extinguished the optical-fibre fire within 3 min and the UPS-component fire within 2 min; the ignition range of the UPS combination was relatively small compared with optical fibre.

Limits: it is a small-scale, preliminary study; airflow in full-size rooms, occupant safety under oxygen depletion, low-temperature tolerance of equipment and nitrogen storage are unresolved. It supports exploration rather than design values.

Key points

1. Chinese computer-room design rules allow gaseous agents (HFC-227ea, IG541, aerosol) and water-based systems (pre-action, high-pressure fine water mist); the authors argue gaseous agents are costly and water damages equipment.
2. The test rig was a 1 m acrylic cube containing six 25 cm × 25 cm × 35 cm boxes representing computers, scaled with Froude scaling (Q_M/Q_F = (l_M/l_F)^(5/2)).
3. Injected liquid nitrogen must occupy more than 33% of the fire-site space; injected mass was limited to less than 0.65 kg because electronics tolerate low temperature differently; initial temperature about 20 °C.
4. With the 6520# nozzle the minimum container-side temperature fell to about 10 °C within 300 s, against about 12 °C within 600 s for 6510# and 16 °C for 6530#; solid-cone nozzles were prone to frosting and blocking.
5. For the best nozzle, relative temperature changed by more than 50% within 5 min and oxygen concentration dropped below 10%.
6. Liquid nitrogen extinguished the optical-fibre fire within 3 min and the UPS-component fire within 2 min.

Using it in design

• When assessing non-gas, non-water suppression options, note liquid nitrogen only as a preliminary-stage option, and ask for full-scale testing and an occupant-safety analysis for oxygen depletion before taking design values.
• In inerting approaches where oxygen falls below 10%, make personnel evacuation and access control a mandatory part of the suppression design.
• Document the test data that limited injected nitrogen mass and nozzle type for low-temperature-exposed electronics as the basis.

Who should read it

Fire-safety engineers investigating gas-free and water-free suppression alternatives for data-centre computer rooms.

Document contents

1. 1. Introduction
2. 2. Materials and Methods (2.1 Simulation Test System, 2.2 Simulation parameters and data acquisition and processing, 2.3 Test)
3. 3. Results and Discussion (3.1 The Variations of Temperature in Cooling Process, 3.3 Extinguishing Effects of Liquid Nitrogen on Optical Fiber Combustion, 3.4 Extinguishing Effects of Liquid Nitrogen on Combined Combustion of UPS)
4. 4. Conclusions

Related standards

• NFPA 2001
• NFPA 75
• GB 50174

Read the document

Publication details

Authors

Jianbing Meng; Tingrong Wang; Guanghua Li; Jianhong Kang

Publisher

Fire (MDPI AG)

Year

2023

Volume

6

Issue

3

Pages

116

Document language

English

Source type

Scientific

Access

Open licence — downloadable

DOI

10.3390/fire6030116

Licence

CC BY 4.0 — share with attribution

Licence evidence

www.mdpi.com

Citation