Development of a Liquid Cooled Rack Specification

Development of a Liquid Cooled Rack Specification

About the Project

Project Background & Purpose

There are currently no common specifications with most liquid cooling solutions being unique and proprietary. Such lack of standards and lack of multi-source solutions are seen as impediments to wide market adoption of liquid cooling. Influential market players could drive faster development and adoption of such technology for the benefit of themselves as well as the industry. Many vendors have entered the market with liquid cooling solutions, however most/all are proprietary and generally non-compatible with each other. This is acceptable for some homogeneous compute environments, but less acceptable for non-homogeneous compute environments where standard multivendor solutions are strongly preferred. Buyers in the market would benefit from greater standardization. The hypothesis is that incompatible proprietary systems are a market barrier that will continue to inhibit adoption of warm liquid cooling.

The scope of this project is to develop an open specification for the secondary fluid (closed loop between the CDU and the IT equipment), manifolds, tubing, quick connectors, and the operating conditions. It does not include the CDU or the heat exchangers in or on the IT equipment. The goal of the project is to develop a liquid cooled rack specification that could accommodate multiple vendors and provide a reusable infrastructure for multiple refresh cycles with a variety of liquid cooled servers/suppliers.  The specification could include but is not limited to, fluid selection and quality, supply pressure, temperature, and flow, delta pressure and temperature, header size and material, connection spacing, size, and details. 

Merging with OCP's Advanced Cooling Solutions Project

The Open Compute Project (OCP) has initiated the Advanced Cooling Solutions (ACS) project. The ACS project shall create specifications, standards, support documentation, or reference designs which enable global adoption of liquid cooling for the data center equipment with the goal of harmonization of liquid cooling solutions that benefit OpenRack and Olympus (EIA-310 compatible) based products as well as Project Scorpio in China. The initial working group effort (see below) is now being merged and continued through ACS. This will help ensure that the final specification will be compatible with server rack designs promulgated by multiple open standards organizations such as Project Scorpio (China), the Open Compute Project (OCP), and Open19. Parties interested in getting involved in the effort should contact

Project Progress & Focus

The Open Specification for a Liquid Cooled Server Rack Progress Update document details the accomplishments made by the working group so far. The working group has focused on the following specifications:

  • The wetted material list (all components must be compatible with this list)
  • Water based transfer fluid quality and treatment
  • Proposed fluid operating ranges
  • A universal (multi-vendor) quick connect
  • General operating specifications (such as pressure and temperature ranges)

Related Working Group Effort

Initial efforts of the project were housed under a bilateral initiative from the U.S. Department of Energy (DOE) and China’s Ministry of Industry and Information Technology (MIIT) to increase efficiency in data centers. The Lawrence Berkeley National Laboratory (LBNL) and China Institute of Electronics (CIE) steer this initiative and coordinate the contributions of industry stakeholders. A small working group of influential potential users/buyers of warm liquid cooled equipment that are active in open standards organizations was formed.

Learn more about this phase of the project here. 

View white paper detailing the resulting specifications from this project phase.

Relevant Documents

  • Open Specification for a Liquid Cooled Server Rack Progress UpdateThis document is a progress update on the development of an open specification for a liquid cooled server rack, including the proposed wetted materials list, wetted materials to be avoided, proposed fluid operating ranges, fluid thermo-physical properties, fluid quality, and other considerations. 
  • Open Specification for Liquid Cooled Rack – Transfer Fluid (Draft)This draft specification on transfer fluid is one section of a comprehensive Specification for the overall Liquid Cooled Rack System. Compatibility is driven by the wetted materials, the transfer fluid, connectors, and operating conditions (e.g., temperatures and pressure).  In the case of the transfer fluid, compatibility is particularly important with the wetted materials list. 
  • Presentation- Harmonization of Open StandardsSlides from presentation given at the Data Center Dynamics Conference in San Francisco in June, 2018. The presentation covers the working group effort to develop a liquid cooled rack specification. 
  • CoE Liquid Cooling PageLiquid cooling is valuable in reducing energy consumption because the heat capacity of liquids is orders of magnitude larger than that of air and once heat has been transferred to a liquid, it can be removed from the data center efficiently.