Guidelines and Base Specification for Dielectric Fluid-Based Two-Phase Cold Plate Heat Transfer Fluid

Author: Shahar Belkin, ZutaCore Collection: 2026-OCP-EMEA-Summit-Cooling-Environments-And-Liquid-Cooling

Summary

This presentation introduces two OCP documents from the Cooling Environments — Cold Plate workstream: (1) the Guidelines document (already published and available) and (2) the Base Specification (submitted and in review at time of presentation, planned publication within weeks). Both documents are led by Lilac Bussmann from ZutaCore and address dielectric fluids used in two-phase cold plate liquid cooling systems. The motivation is identical to the broader industry push: GPU and CPU TDPs are rising beyond what single-phase water-based systems can handle economically, and two-phase dielectric fluids offer higher heat transfer capacity per unit flow rate. The OCP workgroup deliberately prioritized multi-vendor interoperability — learning from the single-phase water era where vendor lock-in created deployment friction — so that operators can select fluids from multiple vendors without re-qualifying their entire cooling infrastructure.

The Guidelines document covers fluid selection criteria (ASHRAE A1/A2L classification, low GWP, zero ODP, non-conductive), system design and operation practices, installation and maintenance (filtration, monitoring, no replacement needed over system lifetime of 20–30 years), and lifecycle handling including reuse. The Base Specification codifies mandatory measurable properties: boiling point range −50°C to 60°C at atmospheric pressure; latent heat ≥100 kJ/kg; density >800 kg/m³; dielectric strength ≥30 kV; toxicity ASHRAE Class A; flammability Class 1 or 2L; GWP <700 (with a recommendation to select <10); ODP ~0. Validation requires ASTM D471 material compatibility testing — long-term exposure at the fluid's boiling point with less than 5% change in sealing weight, stiffness, and volume. Fluid purity must comply with AHRI 700. The key operational insight is that these fluids do not need to be replaced over the system lifetime, require only 100 µm filtration (no biological growth, no corrosion), and operating pressure is low enough that maintenance is minimal.