Liquid Cooling in Data Centers
Where traditional air cooling reaches its physical limits, liquid cooling ensures stable temperatures in data centers. Precise monitoring is essential for efficient and safe operation of the cooling circuit. wenglor flow sensors enable precise flow monitoring, protect against failures and ensure trouble-free cooling. In addition to the flow sensors, pressure sensors can be installed to ensure reliable pressure monitoring in the cooling circuit.
At a Glance: Sensors for Reliable Liquid Cooling
Adapted to Different Cooling Media
Variants for deionized water, normal water and PG25 take into account the different thermal properties of the coolants and enable reliable flow monitoring.
Flexible and Adjustable
The portfolio offers flow sensors with different probe lengths and process connections – ideal for different pipe diameters and applications.
Stainless Steel 316L Housing with IP69K
The sensors feature a durable and robust stainless steel 316L housing, and IP69K protection class ensures durability in harsh industrial environments.
Small Measuring Point
Thanks to the small measuring point on the flow sensors, the cooling circuit is hardly influenced and the pressure drop in the system is reduced to a minimum.
Compact and Resistant to Cleaning Agents
Thanks to the compact design and hygienic sensor surface, no dirt, germs or deposits can accumulate in the dead spaces.
Dirt-Resistant
There are no moving parts on the sensor, which makes it wear-free and extremely resistant to deposits and dirt.
Why Is Liquid Cooling so Important in Data Centers?
Modern data centers are under ever-increasing pressure to perform – especially due to the boom in artificial intelligence and the increasing number of data-intensive applications. The increasing demand for computing power, ever faster servers, more powerful processors and CPUs (Central Processing Units) lead to enormous energy consumption and thus to significantly more waste heat. While, in the past, the generated heat could be dissipated with conventional air cooling, this is often no longer sufficient due to the high heat loads. This is where liquid cooling comes in. This type of water cooling uses the high thermal conductivity of water or other liquids to absorb and efficiently dissipate this heat directly at the source – in the racks.
Flow sensors are used to ensure reliable water cooling at the rack and in the CPUs. These sensors are mounted in the pipes inside the CDUs and ensure reliable flow monitoring. They also protect against failures and overheating. In addition to the flow sensors, weFlux² series pressure sensors can also be installed in the pipes of the coolant circuit. This means that, not only is the flow measured, but the water pressure in the pipes is also continuously checked.
How Does Liquid Cooling Work?
Liquid cooling has two cooling circuits. The primary circuit is responsible for external cooling. The heated liquid is removed from the data center and cooled via cooling units such as cooling towers or chillers. The secondary circuit returns the cooled liquid directly to the servers or racks. Between these two circuits is a central unit, the CDU (Coolant Distribution Unit). It separates both circuits, e.g. via a plate heat exchanger, and ensures that no contaminated water from the primary circuit enters the IT area of the secondary circuit.
Server Rack
CDU (Coolant Distribution Unit)
Primary Circuit
Secondary Circuit
Flow Monitoring in the Primary and Secondary Circuit
Primary circuit
Secondary circuit
weFlux² flow sensor
weFlux² flow sensor
weFlux² flow sensor
weFlux² flow sensor
Primary Circuit
The primary circuit connects the cooling unit outside the building to the coolant distribution unit, or CDU for short. As the pipes are partly exposed to low ambient temperatures, water or the frost-proof water-propylene glycol mixture PG25 is used, depending on the application. Flow sensors with correspondingly long measuring rods are suitable for larger pipe diameters.
Secondary Circuit
The secondary circuit runs between the CDU and the racks or servers inside the building. Water, deionized water or glycol mixtures at temperatures up to 60 °C are used as cooling media. Consistently high media quality is a prerequisite for reliable operation of the cooling circuit. Flow sensors monitor the supply and return and contribute to an even coolant supply.
Which Medium Is Used for Liquid Cooling?
The choice of cooling medium depends on the system architecture, the ambient temperatures and the requirements for heat transfer and frost protection. In liquid cooling systems, water, deionized water and water-propylene glycol mixtures are mainly used. Since their thermal and electrical properties differ, the sensors must also be adapted to the respective medium.
Water
Water is readily available and has a high thermal conductivity. However, without appropriate treatment, corrosion and biological deposits can occur in the cooling circuit.
Deionized Water
Deionized water is fully desalinated or demineralized and enables efficient heat transfer. Depending on the system, additives are added for passivation of metals and for biocontrol. Due to the low electrical conductivity, conventional magnetic-inductive flow sensors are not suitable for this application.
PG25
PG25 consists of 25 percent propylene glycol and 75 percent water. The glycol content typically protects the system from freezing down to approximately −10 °C. At the same time, PG25 has approximately three times the viscosity of water at 25 °C. As a result, the thermal conductivity is slightly reduced and the pumps require more energy. Additives can also reduce corrosion and biological activity.
Suitable Flow Sensors for Different Cooling Media
| Applications | Recommended sensors | |
|---|---|---|
| Water and deionized water | Primary and secondary circuits if no frost protection is required | |
| PG25 | Primary and secondary circuit with requirements for frost protection |
The following applies to both sensor versions: Installation is possible regardless of the flow direction.
weFlux² Pressure Sensors for Pressure Monitoring
Versatile Use in Existing and New Systems
- weFlux2 pressure sensors can measure pressure and temperature simultaneously
- Reliable pressure measurement of gaseous and liquid media
- Wide range of output functions
- Depending on the product variant, with IO-Link interface for quick and easy parameterization
- Also available with display for direct reading of process values
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