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

Overview

The specification is a product of the OCP Cooling Environments cold-plate sub-project and focuses exclusively on dielectric fluids used in cold plate liquid cooling; in the document 'dielectric fluid' means two-phase dielectric fluid. In two-phase cooling the liquid boils at the chip and absorbs latent heat, the vapour moves to a condenser and returns to liquid. The text says this gives better heat removal than single-phase liquid cooling, reduces short-circuit risk on leaks because the fluid is non-conductive, and lowers water consumption.

Essential fluid properties are listed: heat transfer effectiveness, electrical insulation, boiling point, viscosity, oxidation stability, material compatibility, flammability, toxicity and environmental impact. Four fluid families are compared. PFCs have excellent dielectric properties but very high GWP. HFEs offer lower GWP with slightly weaker dielectric properties. HFCs are widely available but carry higher GWP. HFOs are the newer generation with ultra-low GWP, good chemical stability and material compatibility.

The numeric requirements are: boiling point -50 to 60 C at 1 atm (application-dependent), latent heat of vaporization at least 100 kJ/kg, density above 800 kg/m3 at 25 C, operating temperature 4-75 C and storage -20 to 60 C. On safety, ASHRAE 34-2022 flammability class 1, with 2L acceptable in some uses, and typically an 'A' toxicity class. For GWP the text cites the US EPA AIM Act requiring refrigerants below 700 in new data centre cooling equipment and notes new European chiller refrigerant rules from 2027.

The validation plan covers prolonged metal and polymer exposure per ASTM D471, simulated ageing of 1,000 hours at 60 C (or 7 or 14 days at 100 C or higher) followed by GC-MS analysis, oxidation and flammability validation, and purity testing to AHRI 700-2024. Fluid purity is monitored annually and make-up fluid compensates minor evaporative losses and leaks. It is a short base specification; it names no product and sets class-level criteria only.

Key points

1. Scope is two-phase dielectric fluid only, for cold-plate direct-to-chip cooling.
2. Families compared: PFC (excellent dielectric, very high GWP), HFE (lower GWP), HFC (widely available, higher GWP), HFO (ultra-low GWP, good stability and compatibility).
3. Boiling point -50 to 60 C at 1 atm (application-dependent); latent heat at least 100 kJ/kg; density above 800 kg/m3 at 25 C.
4. Thermal performance must remain stable after laboratory testing that simulates five years of operation.
5. Flammability class 1 per ASHRAE 34-2022 (2L acceptable in some cases); toxicity typically class 'A' (for example A1).
6. US EPA AIM Act requires GWP below 700 for new data centre cooling equipment; EU chiller refrigerant rules change from 2027.
7. Operating temperature 4-75 C and storage -20 to 60 C; fluid purity monitored annually.
8. Validation: ASTM D471 material exposure, 1,000 h at 60 C (or 7-14 days at 100 C or higher) ageing then GC-MS, AHRI 700-2024 for purity.
9. No degradation or polymerization in the presence of copper, aluminium or stainless steel.

Using it in design

• Record ASHRAE 34 safety class, GWP, ODP, boiling point and latent heat in the two-phase cold-plate fluid catalogue.
• Warn when a selected refrigerant exceeds GWP 700 for US projects, and trigger a ventilation and refrigerant-safety review (for example EN 378 / ASHRAE 15) for class 2L fluids.
• Select the boiling point together with system pressure and condenser temperature; the document says boiling-point choice balances heat absorption against system pressure.
• Include annual fluid purity sampling and make-up fluid in the O&M plan, and account for that make-up in two-phase CDU sizing.
• In the wetted-material check require the supplier's ASTM D471 results for copper, aluminium, stainless steel, polymers and elastomer seals.
• Treat the future direction of PFAS and GWP regulation as a risk in fluid selection.

Who should read it

Cooling engineers, system integrators and fluid suppliers selecting two-phase cold-plate systems.

Document contents

1. License
2. Compliance with OCP Tenets
3. Scope
4. Overview
5. Base Specifications
6. Description
7. Goals and Vision
8. User Requirements/User Stories
9. Key Properties and Types of Dielectric Fluids for cold plates
10. Essential Fluid Properties
11. Types of Dielectric Fluids
12. Requirements
13. Thermal Performance Requirements
14. Density
15. Boiling point
16. Safety, Environmental and Chemistry requirements
17. Constraints
18. Test and Validation Requirements
19. Compliance
20. References
21. Appendix: Glossary

Related standards

• ASHRAE Standard 34-2022
• US EPA AIM Act Technology Transitions rule
• ASTM D471
• OCP Guidelines for Dielectric Fluids in Two-Phase Cold Plate Racks

Read the document

Publication details

Authors

Belkin, S.; Butchmits, L. (ZutaCore); contributors incl. Chemours

Publisher

Open Compute Project Foundation

Year

2026

Document number

v1.0.0

Document language

English

Source type

Industry body

Access

Open licence — downloadable

Licence

OWFa 0.9 — Open Compute open specification licence; redistribution permitted

Licence evidence

www.opencompute.org

Citation