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Solving the heat dissipation problem of 5G base stations
release time:2021-04-28 16:21:04Publisher: Tycooler

On June 3, Nokia announced in Espoo, Finland, that its 5G AirScale liquid-cooled base station solution has helped Finnish mobile operator Elisa to reduce the potential energy costs of its base stations by 30% and reduce carbon dioxide emissions by about 80%. This is the first deployment of a commercial 5G liquid-cooled base station solution in the world, demonstrating Nokia's firm commitment to sustainable development and climate change.


Screenshot of NOKIA liquid-cooled 5G base station press release

While reducing energy and emissions, Nokia said that liquid-cooled base stations run quietly and require no maintenance. In addition, compared with standard active air conditioning equipment, the volume is reduced by up to 50% and the weight is reduced by 30%. Liquid cooling technology saves a lot of operating costs for base station site operators and extends the service life of base station components as much as possible.


NOKIA 5G AirScale liquid-cooled base station

It is reported that Nokia announced its successful deployment of the world's first 5G liquid-cooled base station system on its official website on December 10, 2018. At MWC in 2017, Nokia once demonstrated Bell Labs liquid-cooled base station technology. With the continuous evolution of wireless technology from 2G to 5G, the power consumption of base stations is 2-3 times that of the 4G era. The traditional air-cooling system is about 4000 times smaller than water because of the heat capacity of air. Compared with the liquid cooling system, the traditional air-cooling system Energy efficiency is too low. Therefore, 5G base stations require more advanced liquid cooling systems.

Liquid cooling is a kind of cooling technology suitable for high-power power electronic equipment, using the large specific heat capacity of the liquid cooling medium to quickly take away the heat of the equipment. 
The current application and development focus includes single-phase liquid cooling, two-phase liquid cooling, immersion liquid cooling, spray liquid cooling, etc. In the first two liquid cooling technologies, the cooling medium does not directly contact the electronic devices, while the latter two liquid cooling technologies use dielectric liquids to directly contact the electronic devices, and the cooling effect is the best. 

Single-phase liquid-cooled coolant is driven by a pump and flows in the channel to take away heat. The most common application is water-cooled plates, which is a relatively mature technology. The cost of water-cooled plates is mainly concentrated in materials, runner forming and welding. 

The topological design of the flow channel of the water-cooled plate and the integrated process of simple flow channel grooving, sealing and welding are the two frontiers we have learned so far. 
The flow channel topology design, according to the explanation of Toyota researchers, is to combine jet impingement and runoff based on the optimized branched cooling channel in the heat sink, which can eventually take away most of it evenly while minimizing the pressure drop. Heat, without the need to install a large pump to increase the coolant flow rate, resulting in energy waste. 

The picture below shows the prototype of a liquid-cooled plate designed by Toyota using COMSOL Multiphysics® software for simulation topology design.


The picture on the left is a prototype of an aluminum heat sink with a layered micro-channel topology; the picture on the right is a prototype of an aluminum heat sink without a topology.

Now, we can also use AI computing technology to develop a topological design runner liquid cooling plate with a cooling efficiency increase of 20%.


Diabatix company uses AI to drive the topological design of the flow channel of the liquid-cooled radiator. The design is optimized for uniform surface temperature. The design method automatically considers flow restrictions (flow rate, pressure drop), thermal properties of the materials used, and manufacturing restrictions (such as CNC milling). Compared with the traditional design, under the same flow conditions, an efficiency improvement of up to 20% can be achieved.

For the one-time grooving and sealing welding of the simple runner of the water-cooled plate, please refer to our other report for details: Coreflow: TWI new machining technology, or trigger a revolution in the water-cooled plate industry.

Next, we will briefly introduce the two-phase liquid cooling. Two-phase liquid cooling is an efficient cooling technology that uses the latent heat of vaporization of the liquid medium (the latent heat is much larger than the single-phase sensible heat) to quickly remove heat. 

The two-phase liquid cooling product we are most familiar with is the Vapor Chamber. The Vapor Chamber can be combined with the cold exhaust to form an internal circulation system. The liquid reflux does not require a pump drive. It is under the action of vapor pressure or gravity or capillary force. Bottom, realize the internal return circulation (closely related to the installation position). 
In addition to the internal circulation two-phase liquid cooling, we can also add a low-power magnetic pump to achieve a pumping two-phase cooling system. Compared with single-phase liquid cooling, pumped two-phase cooling technology can bring twice the cooling efficiency.


Schematic diagram of ACT's pumping two-phase cooling system


The cooling medium of the pumped two-phase cooling system evaporates at the heat source, and the latent heat of evaporation quickly takes away the heat (picture source: ACT) 

The above briefly introduces the non-contact liquid cooling technology. Whether it is single-phase liquid cooling or two-phase liquid cooling, cold plates and pipelines are required to form a cooling liquid circulation system. Contact liquid cooling, that is, immersion liquid cooling, in which the electronic components of the circuit board are directly immersed in the dielectric cooling liquid, is currently the most efficient cooling technology. 

With the acceleration of 5G high-speed basic network construction, the cooling demand trend of 5G base stations, cloud computing, edge computing and other data centers is increasing, and efficient and fast cooling, reducing volume and weight, convenient deployment, and reducing operation and maintenance costs are the industry's concern for heat dissipation solutions. Focus. 

Information source: Nokia/Toyota/ACT, etc., for industry exchanges only!
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