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KAORI Heat Treatment Ltd


Demonstrating the superiority of liquid immersion cooling over air-cooling or direct-to-chip (D2C)

Project Overview

When it comes to thermal management, data centre infrastructure is still predominantly based on air cooling technology. Consequently, it is standard practice to retrofit air-cooled servers for use in immersion cooled systems. If the servers were originally designed to function in air-cooled systems, how can they be expected to perform immersed in a dielectric fluid?

The purpose of this technical white paper, based on results from a proof-of-concept study conducted by KAORI Heat Treatment Ltd. and the MIVOLT team, is to demonstrate the suitability and benefits of immersion cooling a retrofitted server (designed for air cooling) from SuperMicro in a synthetic ester fluid – MIVOLT DF7. The main areas of focus are to analyse thermal performance and understand material compatibility in an immersion cooled system with a synthetic ester fluid.

The Challenges

1- Adaptations

Adaptations were necessary in order for the air-cooled server to operate in the immersion system. One example is the motherboard firmware, which had to be modified to allow the server to run without fans.

2- Thermal Performance

Thermal management is critical to sustain data centre performance and protect components. This proof-of-concept study would need to demonstrate improvements in thermal management without any disruption to components when a server is immersed in MIVOLT.

3- Energy Consumption and Power Savings

Energy is usually the largest operating cost for data centres. Therefore, this study would need to illustrate how liquid immersion cooling could reduce costs and lead to power savings.

4- Compatibility

One of the major concerns surrounding liquid immersion cooling is material compatibility, will the dielectric liquid cause corrosion or affect the materials in the server components? It was therefore necessary for this study to closely examine the interaction between MIVOLT and server components.

The MIVOLT Solution

The immersion system (provided by Kaori Heat Treatment Ltd.) was an all-in-one solution integrating a 2U tank and a 3 kW air-cooled Cooling Distribution Unit (CDU). The system included a monitoring system that allowed for data collection from the tank, such as inlet and outlet temperatures, coolant flow rates and power data from the Power Distribution Unit (PDU).

MIVOLT DF7 was the dielectric synthetic ester fluid selected for this study. Liquid immersion cooling with MIVOLT was the perfect choice, as it maximises PUE (Power Usage Effectiveness), enhances performance and assures reliability. The following results were observed:

1.

Thermal Performance

Clear benefits with MIVOLT liquid immersion cooling were achieved, especially at a high ambient temperature of 40°C, at which the server would not operate under if air-cooled.

2.

Power Savings

Significant power savings of up to 20% were achieved with liquid immersion cooling solely by removing the Central Processing Unit (CPU) and Graphics Processing Unit (GPU) fans.

3.

Energy Consumption

Energy consumption was reduced by 71% compared to an average air-cooled data centre facility (an average annual PUE of 1.55 was reported by Uptime Institute in 2022).

4.

Material Compatibility

No significant interaction of the server components and immersion system was observed, which demonstrates the suitability of using MIVOLT in server cooling applications.

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