Liquid cooling

Technical guidePDFEditor’s pick

Open Compute Project Foundation · 2023

Guidelines for Using Water-Based Transfer Fluids in Single-Phase Cold Plate-Based Liquid-Cooled Racks

Write the Table 1 targets (TSS, TDS, conductivity, copper and iron, pH, hardness, turbidity, bacteria, azole inhibitor, chloride) into the fluid specification as acceptance criteria and request a certificate of analysis from the supplier.

• pH 8.0-10.5; total hardness below 30 ppm (below 2 ppm for fresh fill); turbidity below 5 NTU.

Liquid coolingWaterCommissioning

Read / Download

Technical guideFree to read

Energy Efficient HPC Working Group / Lawrence Berkeley National Laboratory · 2011

"Hot" for Warm Water Cooling (SC11 State of the Practice paper, LBNL-5128E)

Implement this stack-up as a design check: from the site's 99.6% design wet and dry bulb plus per-component approaches, compute the achievable chiller-less supply temperature.

• About 90% or more of heat is typically removed by liquid in the solutions considered.

Liquid coolingCoolingEnergy

StandardFree to read

ASHRAE (announcement via HPAC Engineering) · 2011

2011 Thermal Guidelines for Liquid Cooled Data Processing Environments (ASHRAE TC 9.9 White Paper)

In liquid-cooling design, tag facility water loops by W-class, noting that later editions may rename or revise them.

• Class W1 facility water supply is 2-17 C.

Liquid coolingCooling

StandardCitation

ASHRAE · 2019

2019 ASHRAE Handbook-HVAC Applications, Chapter 20: Data Centers and Telecommunication Facilities

Cite cooling design rules in an edition-aware way, distinguishing the 2019 and 2023 Handbook editions.

• This is the 2019 edition; the 2023 edition is a separate library entry.

CoolingAirflowLiquid cooling

Technical guideFree to read

Data Center World / AFCOM · 2026

2026 Data Center Trends: AI, Cooling & Power Insights (AFCOM State of the Data Center session, Bill Kleyman)

Use AFCOM density figures (16 kW average; 50-70 kW for AI) as reference bands in the rack-density selector.

• 80 percent of respondents report workloads moving from public cloud back on-premises.

RacksLiquid coolingEnergy

Technical guidePDF

Open Compute Project Foundation · 2024

30 C Coolant - A Durable Roadmap for the Future, Revision 1.0 (Oct 2024)

Default the liquid cooling design wizard to an S30 (30 C) TCS supply with a 6 C CDU approach (24 C FWS) and 1.5 LPM per kW.

• Typical CDU flow design is cited as 1.5 LPM per kW; CDU approach temperature is typically 4-8 C.

Liquid coolingCoolingEnergy

Read / Download

Research paperPDF

Energies (MDPI AG) · 2025

A Review of Non-Uniform Load Distribution and Solutions in Data Centers: Micro-Scale Liquid Cooling and Large-Scale Air Cooling

For high-heat-flux chips, weigh the pump-power increase of complex microchannel cold-plate geometry against the thermal-resistance gain (for example 11.8%).

• Chip heat flux is described as reaching ultra-high levels of 10^6-10^7 W/m².

Liquid coolingAirflowCooling

Read / Download

Research paperPDF

Fluids (MDPI AG) · 2026

A Review of Thermal Management in Modern Data Centres: Water Usage Effectiveness and Heat Transfer Coefficients

Set WUE targets from the heat-rejection topology (dry, free-cooling, hybrid, evaporative) and not only the server-side cooling technology; WUE depends on the share of heat rejected by evaporation.

• Dry facilities with closed-loop liquid cooling need essentially no water, while evaporative systems typically report WUE up to 2.5 L/kWh.

WaterCoolingLiquid cooling

Read / Download

Research paperPDF

Technology Review for Carbon Neutrality (Tsinghua University Press) · 2025

Accelerating liquid cooling adoption in data centers: necessity, challenges and solutions

For racks where GPU/accelerator thermal design power exceeds 1,200 W, take liquid cooling as a mandatory design input, and weigh the initial cost (about 1.9-2.2 times air cooling) against TCO (up to 20% lower after 4 years, vendor figure).

• Cooling systems in air-cooled data centres consume around 40% of total data-centre energy.

Liquid coolingReliabilityEnergy

Read / Download

Technical guideFree to read

Open Compute Project Foundation · 2021

ACS Door Heat Exchanger Requirements for Open Rack, Revision 1.0

Give rear-door HX catalog entries rated kW, fan power, coolant inlet temperature, flow, pressure drop and active/passive type.

• OCP Ready gear should meet ASHRAE Class A1 allowable conditions on the air side.

CoolingLiquid coolingRacks

Technical guideCitation

Uptime Institute Intelligence · 2024

Air-Assisted Direct Liquid Cooling: An Overlooked Option

Offer a 'liquid-to-air CDU / sidecar' as a DLC option.

• Published as UII Update 233 in Q1 2024.

Liquid coolingCooling

StandardCitation

IEEE · 2023

An Investigation of Multi-Parameters Effects on the Performance of Liquid-to-Liquid Heat Exchangers in Rack Level Cooling (ITherm 2023)

Record controller type and supply-temperature stability (e.g. +/- C) in CDU catalogue entries.

• Fluctuations with amplitude under 1 C could converge into larger oscillations depending on settings.

Liquid coolingOperations

StandardFree to read

ASHRAE · 2024

ASHRAE TC 9.9 technical input to the European Commission on the review of Regulation 2019/424 (Ecodesign of servers and data storage)

Do not hard-code A2 as the minimum class; allow H1/A1 classes for AI racks.

• Letter from ASHRAE TC 9.9 to DG GROW, dated 8 July 2024.

CoolingLiquid coolingEnergy

Technical guideFree to read

National Academy of Engineering, The Bridge vol. 56 no. 1 · 2026

Avoiding Waste Heat through AI Infrastructure Thermal Integration

In the heat-reuse calculator, take coolant return temperature as the key input.

• About 70-80% of data centre heat could be recovered.

Liquid coolingSustainabilityWater

Technical guideFree to read

Data Center Frontier · 2024

AWS Unveils AI Data Center Designs Supporting 6x Increase in Density (David Chernicoff)

Support hybrid air/liquid halls and rack-level or near-rack backup power topologies in the design library.

• AWS claims about 12% more compute power per site from the new designs.

ElectricalLiquid coolingRacks

Technical guidePDF

Open Compute Project Foundation · 2022

Base Specification for Immersion Fluids, Revision 1.0, Version 1.0 (December 1, 2022)

Use the summary table as validation rules for immersion-fluid catalogue entries: flash point, pour point, viscosity, density and dielectric properties.

• Pour point below -30 C; critical temperature above 155 C.

Liquid coolingCoolingFire safety

Read / Download

Technical guidePDF

Open Compute Project Foundation · 2026

Base Specification for Two-Phase Dielectric Fluid-Based Heat Transfer Fluid (Cold Plate), Version 1.0.0

Record ASHRAE 34 safety class, GWP, ODP, boiling point and latent heat in the two-phase cold-plate fluid catalogue.

• Operating temperature 4-75 C and storage -20 to 60 C; fluid purity monitored annually.

Liquid coolingCoolingSustainability

Read / Download

Technical guideFree to read

Open Compute Project Foundation · 2025

Beyond ORv3 HPR Busbars: Enabling Next Gen AI Rack Power Levels with Liquid Cooling (OCP EMEA Summit 2025)

Give rack power distribution components fields for rated current, maximum voltage drop and cooling method.

• Liquid-cooled 750 kW busbar: 15,625 A, 1483 mm2, about 85 kg.

ElectricalRacksLiquid cooling

Research paperPDF

Energies (MDPI AG) · 2023

Conjugate Heat Transfer Modeling of a Cold Plate Design for Hybrid-Cooled Data Centers

In hybrid-cooled racks, represent a cold-plate server as a compact model in room-scale CFD: model the share of CPU heat going to the cold plate (~97%) and the residual escaping to air separately.

• A cited micro data centre with 1.2 kW IT capacity reached a maximum outlet water temperature of approximately 50 °C.

Liquid coolingAirflowRacks

Read / Download

Technical guideFree to read

Motivair · 2025

Coolant Distribution Units (Motivair by Schneider Electric)

Store CDU capacity in the catalog as a table over (primary supply T, secondary supply/return T, fluid) rather than a single kW, and compute available capacity at the project FWS/TCS temperatures.

• MCDU-40 nominal flow 280/240 gpm; pump head 15-51 psi across models.

Liquid coolingCooling

Research paperPDF

Energies (MDPI AG) · 2023

Cooling Technologies for Internet Data Center in China: Principle, Energy Efficiency, and Applications

In China, define project design targets from GB 50174-2017 temperature and humidity limits (18-27 °C, dew point 5.5-15 °C, RH at most 60%) and provincial PUE caps (for example Guangdong 1.25).

• Cooling accounts for about 35-40% of total IDC energy consumption, the second largest consumer after IT equipment.

CoolingEnergyLiquid cooling

Read / Download

Research paperPDF

IEEE Transactions on Components, Packaging and Manufacturing Technology (Institute of Electrical and Electronics Engineers (IEEE)) · 2021

CPU Overclocking: A Performance Assessment of Air, Cold Plates, and Two-Phase Immersion Cooling

For high-heat-flux chips, compare the point at which air cooling throttles (here 3.3-4 GHz) with the clock-rate gain from cold plates or 2P immersion (41-51%) in cooling technology selection.

• Compared with air cooling, cold plates gave up to 41% and 2P immersion up to 51% higher CPU clock rates.

Liquid coolingCoolingRacks

Read / Download

Research paperPDF

Frontiers in Energy Research (Frontiers Media SA) · 2022

Current Status and Challenges for Liquid-Cooled Data Centers

Design the CDU as redundant in liquid cooling and arrange the circulating pump as one duty plus one standby; a CDU failure can paralyse the whole system.

• Cooling systems are cited as consuming 30-50% of total data-centre energy.

Liquid coolingReliabilityCooling

Read / Download

Technical guideFree to read

Open Compute Project Foundation · 2025

Data Center Evolution: Powering the AI Revolution Sustainably (OCP EMEA Summit 2025 keynote, Madhusudan Iyengar)

Rack catalogue entries should carry a distribution-voltage attribute (48 VDC, +/-400 VDC, AC); flag 48 V in-rack designs above roughly 150 kW per rack as needing a sidecar or higher-voltage DC architecture.

• Related: OCP Open Rack V3, OCP Diablo 400 (Mt Diablo) power rack.

ElectricalLiquid coolingRacks

All content and rights belong to the respective authors and publishers. SoSo CAD provides only the citation, its own summary and a link to the source, and is not responsible for the sources' content.