Which is more prone to scaling, immersion liquid cooling or cold plate liquid cooling?

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By combining technical principles with industry practices, the scaling risks of plate-type liquid cooling and immersion liquid cooling differ in certain aspects. Overall, plate-type liquid cooling presents a greater risk of localized scaling, while the scaling risk associated with immersion liquid cooling is closely related to the type of coolant. The specific comparisons are as follows: 1. Plate-type liquid cooling: Local flow channels are prone to scaling, and water quality control is crucial. Plate-type liquid cooling is a form of indirect contact cooling, where the coolant circulates within enclosed metal channels and does not come into direct contact with the server chips. The risk of scaling mainly occurs in the tiny flow channels inside the cold plates, the heat exchangers in the CDU (Cooling Distribution Unit), and the inlet areas of the pumps. The main reasons for this are low local flow velocities and large temperature fluctuations: the diameter of the flow channels in the cold plates is small (usually 1–5 mm), resulting in slow flow rates of the cooling fluid. Additionally, the heat generated by the chips creates large local temperature gradients, which facilitates the precipitation and deposition of trace minerals in the cooling fluid, such as calcium and magnesium ions, as well as other impurities, thus forming scale layers. High water quality requirements are present, but it is difficult to meet them entirely: Cold plate liquid cooling systems typically use deionized water or coolants with low electrical conductivity. However, over time, factors such as aging of pipe seals and the intrusion of external contaminants can still lead to a deterioration in water quality, accelerating scale formation. The system has a complex structure with many dead zones: areas such as the CDU heat exchangers, elbows, and valves are prone to forming fluid dead zones, where suspended particles and crystalline substances can accumulate, gradually leading to the formation of stubborn scale. II. Submersion liquid cooling: The risk of scaling is closely related to the type of coolant, with an overall lower risk level. Submersion liquid cooling is a form of direct-contact liquid cooling, in which the server is completely immersed in the coolant. The risk of scaling depends on the chemical properties of the coolant and the operating mode of the system. There are two scenarios: single-phase submersion liquid cooling (where no phase change occurs in the coolant); in this case, the coolant such as mineral oil or fluorinated fluids only experiences temperature changes during circulation, without any boiling or condensation processes. Such coolants are high-purity organic liquids that contain no minerals, and virtually do not form what is traditionally known as \"scale\". However, over long periods of operation, the coolant may develop gums and sludge as a result of oxidation and decomposition, which attach to the surface of the equipment and reduce its heat dissipation efficiency. Such \"organic contaminants\" are more difficult to remove than inorganic scale. Two-phase immersion liquid cooling (with phase change of the coolant): The coolant (such as deionized water) absorbs heat and boils to become vapor; this vapor is then cooled back to a liquid state in a condenser before returning. Due to the continuous evaporation of coolant, if the water quality used for replenishment is not carefully controlled, scale may form in components such as condensers and return pipelines as a result of mineral concentration. The risk of scaling is similar to that in plate-type liquid cooling systems, but the scaling occurs more frequently in the condensation system rather than in the areas where the chips come into contact with the coolant. III. Summary of Key Differences
Cooling method: Cold plate liquid cooling, Immersion liquid cooling (single-phase), Immersion liquid cooling (two-phase)
Type of scaling: Inorganic scale (calcium and magnesium crystals, impurity deposits), Organic fouling (gels, sludge), Inorganic scale (concentrated mineral crystals)
Locations of scaling: Flow channels in cold plates, CDU heat exchangers, pump inlets; Server enclosures, coolant circulation pipes; Condensers, return pipes, water replenishment systems
Scaling risk level: Medium to high (fouling tends to accumulate in enclosed flow channels), Low (the coolant itself contains no minerals), Medium (depends on the quality of water used for replenishment)
Key challenges in prevention and control: Maintaining water purity, cleaning dead corners in flow channels; Preventing oxidation of the coolant and breaking down organic fouling; Monitoring water quality during evaporation and concentration processes

IV. Conclusions and Recommendations
The scaling risk associated with cold plate liquid cooling is more apparent, as it occurs in specific areas of enclosed flow channels. Prevention and control require high-precision filtration, regular chemical cleaning, and real-time monitoring of water quality. Submersion liquid cooling (single-phase) presents almost no risk of traditional water scale, but attention must be paid to organic fouling resulting from the oxidation of the coolant; this can be addressed by adding antioxidants and replacing the coolant regularly. The scaling risk of submerged liquid cooling (two-phase) is similar to that of cold plate cooling, but the scaling occurs away from the core heat-generating components, so its impact on computing performance is relatively delayed; it is essential to control the quality of the water used for replenishment and the degree of evaporation concentration.