Swiftly Grasp Liquid Cooling(Bookmark for Reference)

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Swiftly Grasp Liquid Cooling(Bookmark for Reference)

What is liquid cooling?

Liquid cooling is a method that uses liquid instead of air to come into contact with the heat source for cooling. Depending on the type of contact between the cooling liquid and electronic components, it is divided into indirect liquid cooling and direct liquid cooling. Indirect liquid cooling is mainly based on cold plate liquid cooling technology, which allows for standardization and generalization. Direct liquid cooling is primarily based on immersion liquid cooling technology and can be further classified into phase-change and non-phase-change types. Although direct liquid cooling is more efficient, it requires higher operational and maintenance costs as well as a more rigorous and complex design.

Indirect liquid cooling

The Principle of Cold Plate Liquid Cooling Technology

Liquid Cooling Plate

 

A liquid cooling plate utilizes liquid as a heat transfer medium, flowing through internal channels within the plate. It is a non-contact liquid cooling technology that achieves cooling of the heat source through heat transfer. In a liquid cooling plate system, heat-generating components such as batteries and server chips do not directly contact the liquid. Instead, heat dissipation is achieved through the assembly of a cooling plate attached to the electronic components requiring cooling.

This approach results in minimal modifications to existing heat-generating components and associated parts, enhancing operability. It is currently the most mature and widely applied liquid cooling solution. (Cooling plates can be produced through various methods such as stamping, brazing, CNC machining, etc., and different manufacturing processes contribute to distinct performance characteristics of the product).

liquid cooling plate - XD THERMAL
C2M liquid cold tube

Liquid Cooling Tube/Cooling Tube/Serpentine Tube

 

Composed of thermally conductive metal, typically copper or aluminum alloy, the tubes undergo extrusion and corrugation processes to create an internal structure with a specific number of channels. These channels snugly adhere to the surface of battery cells. Typically, one to two rows of battery cells are sandwiched between every two serpentine flat tubes. This design effectively increases the heat exchange surface area on the battery side, promoting a more uniform temperature distribution during the operation of individual cells and reducing the overall temperature difference across the entire battery pack.

Heat Pipe Liquid Cooling

 

The aluminum substrate is CNC machined to mill grooves, and then pre-bent copper pipes are pressed onto the aluminum substrate using a stamping machine. Subsequently, they are brazed together, followed by further processing to create a water-cooling plate. Immersed tube liquid cooling plates typically come in three forms: shallow embedded tube liquid cooling plate, deep embedded tube liquid cooling plate, and double-sided tube-clamping process liquid cooling plate.

Heat Pipe Liquid Cooling

Direct liquid cooling

Immersion Liquid Cooling

 

Immersion liquid cooling, a typical form of direct-contact liquid cooling, submerges the heated electronic components in a coolant (cooling liquid). It relies on the circulation of liquid to remove heat. Due to the comprehensive direct contact between the heat-generating components and the coolant, immersion liquid cooling offers higher heat dissipation efficiency compared to traditional cooling methods (air cooling and liquid cooling). Additionally, it tends to have lower noise levels compared to cooling plates or spray liquid cooling.

Splash Liquid Cooling

 

Splash liquid cooling is a precision spray, direct-contact liquid cooling technology designed for electronic devices. The cooling liquid can be directly sprayed onto the heat-generating components of IT equipment or solid thermally conductive materials connected to them, either by gravity or system pressure. This enables heat exchange, achieving thermal management for IT equipment.

liquid cooling VS air cooling

The application fields of liquid cooling

Early liquid cooling technologies were primarily developed to replace fans and enhance heat dissipation efficiency. By 2010, as liquid cooling technology continued to improve, its applications gradually expanded. From years of experimentation and implementation, it is evident that liquid cooling technology is now widely employed in the thermal management systems of various electronic devices, the cooling systems of electric vehicle battery packs, as well as in automotive components, machinery, electrochemical energy storage, and many other fields. The technology has matured significantly. Currently, the majority of server chips utilize microchannel cold plates, and new energy electric vehicles employ stamped liquid cooling pipes or liquid cooling plates.

Taking the example of new energy vehicles—liquid cooling systems for power batteries

Due to the impact of temperature on the capacity, safety, and lifespan of electrochemical energy storage systems, it is necessary to implement thermal management for the power battery system of new energy vehicles.

Liquid Cooling System Components

The liquid cooling system utilizes the high heat capacity of the coolant, which can circulate to remove excess heat from the battery system, achieving optimal operating temperature conditions for the battery pack. Its basic components include: radiator (liquid cooling plate/liquid cooling tube), cooling fan, expansion tank, coolant pump, coolant, liquid cooling circuit (including hoses, high and low-pressure wiring, temperature sensors, valves), and liquid cooling unit (optional heater), among others. Liquid cooling systems often require more complex and stringent structural designs to prevent the leakage of liquid refrigerant and ensure uniformity among individual cells within the battery pack.

Thermal Management Solutions

The thermal management solutions for power batteries primarily involve three aspects:

 

1.Cooling of the battery pack: Achieved through the circulation of low-temperature coolant.

2.Preheating of the battery pack: Internal and external heating methods.

3.Insulation of the battery pack: In power battery packs applied in colder regions, the battery box typically requires insulation measures to slow down heat dissipation.

Major Consideration Factors Affecting Cooling Efficiency (including but not limited to):

1.Ambient temperature (operating conditions)

2.Thermal conductivity of battery cells

3.Temperature of the cooling liquid

4.Cooling liquid flow rate/velocity

5.Number of batteries/specific heat capacity

6.Relevant information about the liquid cooling plate

7.Thermal conductivity (thermal conductivity) of the thermal interface

Why Liquid Cooling is Better Than Air Cooling

The advantages of air cooling technology include simplicity, low cost, and easy maintenance. However, its heat dissipation efficiency is relatively lower, and it may not meet the demands of high-performance computing, data centers, and similar fields. Liquid cooling technology may be more suitable in such cases.

Air Cooling vs. Liquid Cooling

Advantages of Liquid Cooling:

 

1.Higher Heat Dissipation Efficiency: Liquid cooling technology can effectively reduce the temperature of devices, enhancing their performance and lifespan. The thermal conductivity of liquid is superior to that of air, allowing liquid cooling to efficiently remove the heat generated by devices.

2.Lower Noise Level: Compared to the noise produced by fans, liquid cooling operates with lower noise, providing a quieter working environment.

3.More Flexible Design: Liquid cooling technology allows for more flexible designs, enabling the installation of radiators and liquid pipelines in different locations to better meet the design requirements of the equipment.

4.More Environmentally Friendly: Liquid cooling can save energy and reduce environmental impact. Compared to the heat generated by fans, liquid can be more easily recycled and reused.

Driving Factors for the Liquid Cooling Market

The overlapping of policies is the main driving factor. Low-carbon economy has been universally recognized worldwide, and both governments and markets place high importance on the green and low-carbon development of industries. Therefore, for industries and business operators, green and low-carbon initiatives, cost reduction, and efficiency improvement are not only requirements of the broader environmental context but also ongoing necessities.

The fundamental reason for the penetration of liquid cooling in the market is the power increase. In the context of data centers, the innovative development of technologies such as 5G, cloud computing, big data, and high-performance AI chips has led to a rapid growth in the scale and quantity of data center construction. According to predictions, by 2025, the average power per cabinet in global data centers is expected to reach 25kW. The vast scale of facilities and the growing demand for computing power make traditional air cooling technologies inadequate to meet the increasing heat dissipation requirements of data centers. Liquid cooling has almost become the ‘only choice’ for the construction of future-generation data centers.

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