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White paperCitation2018

WP#78 - An Introduction to Coolant Distribution Units

The Green Grid · Jason Zeiler, Andrew Wasielewski et al.

The Green Grid's introduction to coolant distribution units (CDUs), which supply coolant at stable flow and temperature under changing load, including cost and risk perceptions of liquid cooling.

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Overview

This white paper (WP 78) is an introduction to coolant distribution units (CDUs). It is dated 17 December 2018; its editor is Jason Zeiler (CoolIT) and it has many co-authors. Download is restricted to members. The paper explains to readers evaluating liquid cooling what a CDU does and why it is needed. This makes CDU selection one of the first steps in a liquid-cooled design.

The main purpose of a CDU is to supply coolant at a stable flow rate and temperature under changing loads. A CDU is typically required to enable a liquid cooling deployment at very high rack densities. According to the paper, liquid cooling can yield CapEx savings despite the added plumbing. The CDU is therefore treated as a critical component of a liquid-cooled system, both for the stability of heat rejection and for protecting the equipment.

The document also discusses perceptions of liquid cooling: perceived risk to IT equipment is a key barrier to adoption. As a limit, the content is known only from the summary on The Green Grid library page; numerical capacity or design values are not part of this record. The paper therefore offers a conceptual introduction rather than detailed selection criteria.

Key points

  1. Dated 17 December 2018; editor Jason Zeiler (CoolIT); download restricted to members.
  2. Main CDU purpose: supply coolant at stable flow rate and temperature under changing loads.
  3. A CDU is typically required to enable liquid cooling at very high rack densities.
  4. Liquid cooling can yield CapEx savings despite added plumbing.
  5. Perceived risk to IT equipment is a key barrier to adoption.
  6. Related references: ASHRAE TC 9.9 Liquid Cooling Guidelines and OCP CDU specifications.

Using it in design

  • In the CDU catalog, hold capacity (kW) at approach temperature, flow, pump head and redundancy.
  • Size CDUs from the TCS heat load.
  • Check the approach temperature against the facility water temperature.
  • In client presentations, add a section addressing the risk perception of liquid cooling.

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Who should read it

Cooling engineers designing liquid cooling and decision makers selecting CDUs.

Related standards

  • ASHRAE TC9.9 Liquid Cooling Guidelines
  • OCP CDU specifications

Publication details

Authors
Jason Zeiler; Andrew Wasielewski; Bob Spears; David Christoffel; Dev Kulkarni; Fred Rebarber; Michael Ellsworth; Yasuhito Nakamura; Peter Frantellizzi; Hitoshi Sakamoto
Publisher
The Green Grid
Year
2018
Document number
WP 78
Document language
English
Source type
Industry body
Access
Citation only
Licence
Copyright retained; citation only — the publisher’s terms apply to the original document
Original licence note

Download requires a free TGG account sign-in (Causeway/member level) and is governed by The Green Grid Terms of Use; summary and facts from the public library landing page; full text not redistributed.

Citation

Jason Zeiler; Andrew Wasielewski; Bob Spears; David Christoffel; Dev Kulkarni; Fred Rebarber; Michael Ellsworth; Yasuhito Nakamura; Peter Frantellizzi; Hitoshi Sakamoto (2018). WP#78 - An Introduction to Coolant Distribution Units. The Green Grid. WP 78. https://www.thegreengrid.org/en/resources/library-and-tools/491-WP%2378---An-Introduction-to-Coolant-Distribution-Units

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