With the explosive growth of AI large models and supercomputing centers, single-rack power density has risen from single-digit kilowatts in the traditional air-cooling era to 30kW or even higher. Liquid cooling technology, with its heat exchange efficiency 50 to 100 times that of air cooling, has become the standard thermal solution for high-density computing centers. In the secondary-side flexible connections of liquid cooling systems, hose selection directly determines system safety, energy efficiency ratio, and total lifecycle cost. EPDM (Ethylene Propylene Diene Monomer) liquid cooling hoses, as one of the most widely used piping materials on the market, play distinctly different roles in the two mainstream liquid cooling architectures: cold plate and immersion cooling.
I. Core Performance Parameters of EPDM Liquid Cooling Hoses
EPDM liquid cooling hoses adopt a multi-layer composite structure: the inner layer is high-purity EPDM rubber with a smooth inner wall to reduce fluid resistance; the reinforcement layer uses polyester fiber braiding or aramid reinforcement to enhance pressure resistance; the outer layer is wear-resistant, weather-resistant, ozone-resistant EPDM rubber. Key performance parameters include: operating temperature range typically from -40°C to +120°C, with special formulations capable of withstanding 150°C to 200°C for short periods; bore size covering 6mm to 25mm; minimum bend radius as low as 2 times the hose diameter, enabling flexible routing in high-density cabinets; maximum working pressure up to 1.6MPa; flame retardancy meeting UL94 V-0 standard. EPDM hoses offer good compatibility with conventional coolants such as water, ethylene glycol, and propylene glycol, with a purchase price far lower than PTFE hoses and stainless steel corrugated tubes.
II. Cold Plate Liquid Cooling: EPDM’s “Home Turf”
Cold plate liquid cooling is currently the mainstream commercial liquid cooling solution for data centers. Its working principle involves direct contact between cold plates and high-power chips such as server CPUs and GPUs, using circulating coolant (e.g., deionized water, ethylene glycol solution) to efficiently remove heat, which is then processed and recirculated through the Coolant Distribution Unit (CDU).
In this architecture, EPDM hoses are the absolute mainstream choice. The core advantages are reflected in the following aspects:
Excellent media compatibility: EPDM offers good chemical stability with water-based and ethylene glycol-based coolants, with minimal swelling or performance degradation. When selecting, it is important to choose EPDM hoses with peroxide-cured formulation to avoid sulfate leaching that could contaminate the coolant.
Outstanding flexibility and installation convenience: EPDM hoses have a minimum bend radius of only 2 times the hose diameter, enabling flexible routing within compact 1U/2U server cabinets. With quick-connect couplings (UQD), single-server piping deployment time can be reduced to 1/3 of that of traditional metal pipes.
Significant cost advantage: EPDM hoses have a purchase price far lower than PTFE hoses and stainless steel corrugated tubes, reducing initial investment costs by over 50%.
Compliant safety performance: EPDM hose covers meet UL94 V-0 flame retardancy standards, providing reliable safety protection in high-heat-density data center environments.
Typical application scenarios: EPDM liquid cooling hoses are primarily used for in-rack CDU-to-manifold connections and cold plate connections of conventional server nodes in general AI clusters (single-rack power ≤30kW).
III. Immersion Cooling: EPDM’s “Forbidden Zone”
Immersion cooling involves fully submerging servers in dielectric coolant, achieving higher cooling efficiency with PUE as low as 1.1. However, immersion cooling is precisely EPDM’s “forbidden zone.”
The core issue is media compatibility. Coolants commonly used in immersion cooling include fluorinated fluids (such as perfluoropolyethers) and synthetic hydrocarbon dielectric fluids. EPDM generally exhibits poor compatibility with these media—multiple major coolant manufacturers list EPDM as having “poor compatibility” in their material compatibility data. EPDM is prone to swelling upon contact with fluorinated fluids, leading to a sharp decline in material properties; in synthetic hydrocarbon dielectric fluids, it also carries the risk of accelerated material degradation.
Therefore, in immersion cooling scenarios, EPDM hoses are replaced by PTFE (Polytetrafluoroethylene) or FEP/PFA fluoroplastic piping. PTFE corrugated cooling hoses can operate stably over a wide temperature range of -60°C to +260°C, with slower aging degradation and longer service life, significantly outperforming EPDM in media compatibility, high-temperature stability, and long-term reliability.
IV. Selection Recommendations and Future Trends
Cold plate liquid cooling (≤30kW/rack) : Prioritize EPDM hoses with UQD quick-connect couplings. When selecting, ensure the product uses peroxide-cured formulation and has UL94 V-0 flame retardancy certification.
Immersion cooling or high-density AI computing scenarios (≥80kW/rack) : Choose corrugated hoses made of PTFE, FEP, or PFA. For metal piping, 316L stainless steel is recommended.
Hybrid architectures or transitional scenarios: Select based on the specific coolant type—use EPDM for water-glycol circuits and PTFE/FEP for fluorinated fluid circuits.
In terms of technological evolution trends, as AI computing density continues to increase, the demand for high-power, high-temperature, long-life, and high-reliability liquid cooling is growing rapidly. Stainless steel corrugated tubes, with advantages such as zero leakage, long service life (15+ years), and full media compatibility, are gradually replacing traditional EPDM rubber hoses in high-density scenarios. However, EPDM hoses will continue to hold a place in low-to-medium-power cold plate liquid cooling systems due to their cost-performance advantage.
Conclusion
EPDM liquid cooling hoses are the most cost-effective mainstream choice in cold plate liquid cooling, but they are unsuitable for immersion cooling due to media compatibility issues. The key to selection lies in clarifying the liquid cooling architecture and coolant type—water-based/ethylene glycol coolants pair with EPDM, while fluorinated fluids/dielectric fluids require PTFE or FEP. Only with precise matching can the long-term stable operation of the liquid cooling system be ensured.
