Data Center Immersion Cooling: Types of Coolants and Their Advantages

Immersion cooling technology in data centers involves submerging servers and other equipment in non-conductive coolants to dissipate heat directly through liquid heat exchange. 

The choice of coolant is critical, with the main types being single-phase liquids and phase-change liquids. Here’s a detailed breakdown:

1. Single-Phase Coolants

 Characteristics: Remain in liquid state without boiling, relying on convection and conduction for heat transfer.  

 Common Types & Advantages:  

  ① Mineral Oil (e.g., 3M Novec, Engineered Fluids' Bolt)  

      - Advantages: Low cost, chemically inert, compatible with most materials (rubber, plastics).  

      - Disadvantages: Higher viscosity may reduce flow efficiency, often requiring pumps.  

 ② Synthetic Hydrocarbon Oil (e.g., Shell Immersion Cooling Fluid)  

     - Advantages: Excellent thermal stability, resistant to degradation, suitable for high-temperature environments.  

 ③Silicone Oil

    - Advantages: Low toxicity, high dielectric strength, ideal for high-voltage applications.  

 Shared Benefits of Single-Phase Coolants:  

    - Simple system design (no phase change to manage).  

    - Low maintenance, no evaporative losses.  

2. Phase-Change Coolants

 Characteristics: Absorb heat through boiling (phase change), with vapor condensed and recycled.  

 Common Types & Advantages:  

   - Fluorinated Liquids (e.g., 3M Novec 7100/7500, Fluorinert FC-72)  

   - Advantages:  

    - Ultra-low viscosity for superior flow and heat transfer.  

    - Low boiling point (50°C–60°C), high latent heat for extreme cooling efficiency.  

    - Non-flammable, non-toxic, and chemically inert, ideal for high-density setups.  

    - Disadvantages: High cost, requires sealed systems to prevent evaporation, may need condensers.  

 Shared Benefits of Phase-Change Coolants:  

  - Far higher heat dissipation than single-phase (5–10x via latent heat).  

  - Best for extreme power densities (e.g., GPU clusters, AI servers).  

3. Emerging Coolant Technologies  

  - Hydrocarbon/Hydrofluoroether Blends: Balance cost and performance while reducing environmental impact (e.g., high GWP concerns).  

  - Ionic Liquids: Non-flammable and thermally stable, but expensive and experimental. 

Selection Criteria

Trends & Challenges

- Environmental Regulations: The EU and U.S. are restricting high-GWP fluorinated fluids, driving demand for alternatives (e.g., 3M Novec 649).  

- Cost Optimization: Single-phase dominates edge data centers; phase-change suits HPC/AI clusters.  

- Material Compatibility: Long-term effects on server components (e.g., seals, cables) require validation.  

The final choice depends on cooling needs, budget, operational complexity, and environmental compliance.