What do you need to know about designing HVAC systems in data centers? (roundtable)

Overview

This piece is a roundtable discussion published in Consulting-Specifying Engineer in 2023. The participants are Bill Kosik, Brian Rener, Ameya Soparkar and Robert Sty. Four mission-critical HVAC engineers describe recent project experience.

On hot-climate design, a Middle East project is described, designed for 120 F ambient with 95-105 F condenser water, sand-trap louvres and 45-degree underground bends. Phoenix ambient exceeds 115 F; the advice is to relocate air-cooled chillers and generators and to use CFD to avoid exhaust and radiant heat recirculation. The piece also touches on air-side economization with fan-wall air handling units.

Project examples include the University of Utah: up to 10 MW, outside air plus direct evaporative cooling, Tier III, PUE 1.2-1.3, with backup air-cooled chillers running less than 5% of the year. A Korean 10 MW site supplies 75 F and 40% RH via direct outside air, switches to mechanical cooling on Gobi dust events, and reaches PUE 1.25. Colocation chilled water loops are set at 44/56 F for general use and 50/60 F for higher-temperature loops to extend water-side economization.

Unusual heat sinks include snow storage, canal water and in-rack CO2, and thermosyphon coolers are said to perform like towers below about 50 F outdoor temperature with no water use. The discussion also covers the energy-water nexus in drought-restricted regions. As a limit, these are experiences from specific projects and may not apply unchanged in another climate or at another load; they do, however, illustrate with concrete examples the design risks met in hot and arid climates.

Key points

1. Middle East project: 120 F ambient, 95-105 F condenser water, sand-trap louvres, 45-degree underground bends.
2. Phoenix ambient exceeds 115 F; relocate air-cooled chillers and generators and use CFD to avoid exhaust and radiant heat recirculation.
3. University of Utah: up to 10 MW, outside air plus direct evaporative cooling, Tier III, PUE 1.2-1.3, backup chillers run under 5% of the year.
4. Korean 10 MW site: 75 F / 40% RH via direct outside air; switches to mechanical cooling on dust events; PUE 1.25.
5. Colocation chilled water loops: 44/56 F general and 50/60 F higher-temperature loops to extend water-side economization.
6. Thermosyphon coolers perform like towers below about 50 F outdoor with no water use.
7. Unusual heat sinks: snow storage, canal water, in-rack CO2.

Using it in design

• Flag hot-climate risks in site design checks: ambient above 115 F, and recirculation between chillers and generator exhaust; suggest CFD.
• Support multiple chilled-water temperature loops per site.
• Report water use alongside energy so dry and evaporative options can be compared.
• For dusty regions, define a changeover scenario to mechanical cooling in the outside-air system.

Who should read it

Mechanical designers doing data center HVAC and site selection in hot and arid climates.

Related standards

• ASHRAE Thermal Guidelines for Data Processing Environments

Publication details

Authors

Bill Kosik; Brian Rener; Ameya Soparkar; Robert Sty

Publisher

Consulting-Specifying Engineer

Year

2023

Document language

English

Source type

Expert / community

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation