How does a liquid cooling system work? What are the components?

Liquid cooling systems use a coolant (usually water or a specialized liquid) to absorb and dissipate heat from the CPU and GPU. The coolant circulates through a water block connected to the heat-generating component, conducts the heat to the radiator, and then exhausts it through a fan.

Air cooling uses heat sinks and fans. However, liquid cooling systems have better thermal conductivity and can handle the thermal stress of high-performance computing workloads, such as overclocking. They run quietly because the fan speed is reduced, and have the advantage of adjustable appearance. Liquid cooling is critical in personal computers and industrial applications because low operating temperatures ensure system stability.

1. Basic principles of liquid cooling

Liquid cooling systems utilize heat conduction and convection. First, heat is conducted from the IHS of the component to the baseplate of the water block. Thermal paste reduces thermal resistance. A heat sink made of copper or aluminum increases the airflow contact area, dissipating heat to the surrounding air.

The liquid cooling cycle begins with the coolant absorbing heat from the water block. The heated coolant is delivered through a pipe to the heat sink, where it circulates through tiny metal channels with thin fins. The heat is quickly dissipated by the fan-cooled fins. The liquid returns to the water block after cooling to absorb more heat. A continuous closed-loop process maintains the ideal temperature of high-performance components.

2. Components of a Liquid Cooling System

(1) Coolant

The heat transfer efficiency of a liquid cooling system depends on the coolant. For example, distilled water is the most common form due to its high specific heat capacity (4.186 J/g°C) and thermal conductivity (0.624 W/mK). The choice of coolant affects system performance, and the pH and conductivity of the coolant need to be regulated to prevent galvanic corrosion between dissimilar metals.

(2) Water Pump

The liquid cooling system circulates the coolant through a water pump. Most centrifugal water pumps have high flow rates and head pressures. When selecting a water pump, the flow rate should be matched to the system resistance to ensure constant flow under different conditions. Reliability is important; the water pump may be designed to run continuously for tens of thousands of hours.

(3) Radiator

The radiator dissipates the heat of the coolant into the environment. The larger the radiator area and the larger the fan, the better the heat dissipation effect. Fin density (FPI, or number of fins per inch) affects performance. A higher FPI increases the surface area but may require a fan with a higher static pressure.

(4) Water blocks

Water blocks transfer heat directly to the coolant. Acrylic top covers are aesthetically pleasing but slightly affect thermal performance. The flexibility of the system determines whether to use a general-purpose or component-specific water block. Component-specific water blocks perform better because they are in closer contact with the heat source.

(5) Tubing and fittings

The tubing and fittings of a liquid cooling system are responsible for transporting the coolant in the loop. Silicone is used in complex loops because of its flexibility and high-temperature resistance. Compression fittings seal better and leak less, while quick-disconnect fittings are easier to maintain but restrict flow. Tubing must be durable and chemically resistant in glycol or other specialized coolant systems to prevent aging.

3. Applications of liquid cooling

(1) High-performance computing (HPC):

In HPC environments, liquid cooling manages the large amounts of heat generated by dense processor clusters. In addition, liquid cooling increases rack density, allowing more computing power to be packed into a limited space.

(2) Gaming PCs and workstations:

Liquid cooling improves the thermal performance of gaming PCs and workstations because the CPU and GPU can maintain peak clock speeds when working at high loads. Liquid cooling reduces thermal constraints, providing consistent frame rates and processing power for rendering and gaming.

(3) Industrial applications:

In industrial environments, liquid cooling helps regulate the heat of high-power electronic devices and machines. It is suitable for automation systems and power electronics. In addition, liquid cooling extends the life of industrial components while preventing overheating, reducing maintenance time and costs in critical operations.

4. Future trends in liquid cooling

(1) Liquid cooling systems are being improved as current data centers face increasing power density and heat. This results in hot spots and reduced efficiency. Therefore, liquid cooling is 50 to 1,000 times more efficient because it handles heat loads by contacting heat-generating components with cooling liquid.

(2) This is particularly important in meeting environmental goals in data centers. Liquid cooling supports sustainability by reducing cooling energy use by 10-20%. Small liquid cooling structures maximize rack density. Hybrid cooling methods combine liquid and air systems, potentially saving operating costs in traditional data centers.