Investigation of Heat Management in High Thermal Density Communication Cabinet by a Rear Door Liquid Cooling System

Overview

To solve the heat-dissipation problem of high-heat-density data centres, the study applies mature transformer-oil cooling technology to the data room and proposes a rear-door oil-cooling heat exchanger (RDHE) at cabinet level. Heat dissipation of liquid-cooled and conventional air-cooled cabinets was compared; cabinet operating temperature, circulating oil system temperature, cabinet exhaust temperature, cabinet heat density, oil flow rates and fan power were analysed. Cabinet, oil and exhaust temperatures, heat-dissipation efficiency, cumulative heat removal and heat-recovery potential were measured at different oil flows and fan speeds, and an energy-balance model was validated against the tests.

Compared with the traditional air-cooled cabinet, the RDHE increased heat-dissipation capacity by an average of 56.2% and by up to 66.6%. For simulated heat-source power of 800-1600 W, average heat-dissipation efficiency of the RDHE was 44.1%. At 7.8 m³/h cooling-oil flow, 7 m/s air speed and an 800 W heat source, heat-dissipation efficiency reached 58.8%. Air-cooled cabinet operating temperature reached as high as 55 °C, while the liquid-cooled cabinet stayed at or below 50 °C.

After heat exchange, oil temperature reached 46.9 °C and cabinet exhaust air 42.8 °C, which the authors propose for domestic hot water or desiccant regeneration. The oil rear door clearly outperformed plain air cooling and produced warm oil and exhaust air usable for low-grade heat recovery.

Limits: the test scale is far below modern high-density racks (800-1600 W), so absolute capacities do not transfer, and the heat sources are simulated. Practical issues of oil cooling such as leakage, maintenance and weight were not examined.

Key points

1. Compared with the traditional air-cooled cabinet, the rear-door oil heat exchanger (RDHE) increased heat-dissipation capacity by an average of 56.2% and by up to 66.6%.
2. For simulated heat-source power of 800-1600 W, average heat-dissipation efficiency of the RDHE was 44.1%.
3. At 7.8 m³/h cooling-oil flow, 7 m/s air speed and an 800 W heat source, heat-dissipation efficiency reached 58.8%.
4. Air-cooled cabinet operating temperature reached as high as 55 °C, while the liquid-cooled cabinet stayed at or below 50 °C.
5. After heat exchange, oil temperature reached 46.9 °C and cabinet exhaust air 42.8 °C, which the authors propose for domestic hot water or desiccant regeneration.

Using it in design

• Consider a cabinet-level rear-door heat exchanger as an option that can raise heat dissipation by 56-67% over air cooling; compare oil or water coolant separately on leakage risk and maintenance.
• Consider the warm oil (46.9 °C) and exhaust air (42.8 °C) leaving the rear door for low-grade heat recovery (domestic hot water, desiccant regeneration).
• Keep in mind the test scale (800-1600 W) is far below modern high-density racks and do not carry capacity values over directly.

Who should read it

Cooling designers evaluating cabinet-level rear-door liquid cooling and low-grade heat recovery.

Document contents

1. 1. Introduction
2. 2. System Description (2.1 System Principle, 2.2 Testing rig, test conditions, test methods)
3. 3. Methodology (3.1 Theoretical Analysis, 3.2 The Energy Balance Model)
4. 4. Results and Discussion (4.1 Comparison, 4.2 Average heat dissipation efficiency, 4.3 Cumulative heat dissipation, 4.4 Potential heat recovery characterization, 4.5 The coefficient of thermal performance, 4.6 The RDHE calculation model)
5. 5. Conclusions

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Publication details

Authors

Wansheng Yang; Lin Yang; Junjie Ou; Zhongqi Lin; Xudong Zhao

Publisher

Energies (MDPI AG)

Year

2019

Volume

12

Issue

22

Pages

4385

Document language

English

Source type

Scientific

Access

Open licence — downloadable

DOI

10.3390/en12224385

Licence

CC BY 4.0 — share with attribution

Licence evidence

www.mdpi.com

Citation