In the previous article of our liquid cooling series, we looked at what infrastructure is needed to establish a liquid cooling environment in a data center, and how the individual components must work together in order to integrate a high-performance liquid cooling system there. In this blog, we now want to focus on the STULZ portfolio and show how modern liquid cooling environments can be operated using the new systems from STULZ.
Combining air cooling and liquid cooling with CyberCool CMU
Liquid cooling supplements air cooling at high power densities
The STULZ company already has more than 50 years of experience in the field of data center air conditioning. As the STULZ portfolio has constantly evolved, it hasn’t only been outstanding quality and high efficiency that mattered: a high level of individualization, which can also cover special requirements, has also always been key for our customer-specific solutions.
In recent years, a marked trend has been apparent in the global data center market: ever higher power densities – mostly on footprints that have remained the same. This development brings new challenges, especially where cooling is concerned. This is due to increasing demand for power intensive applications, for example in AI, autonomous driving, medicine, and science. To keep the high-performance computing environments needed for these technologies sufficiently cool, liquid cooling is growing in popularity, because liquid can absorb and discharge considerably more heat than air can.
Experts believe that about 50 percent of all servers will be liquid-cooled as early as the year 2030. STULZ had already identified this trend a long time ago. To enable us to offer individual solutions to customers with particularly high power densities, STULZ design engineers brought their experience to bear in the design of powerful liquid cooling components that can be seamlessly integrated in existing data center air conditioning systems and can also be combined with other STULZ products.
However, air cooling is still the method of choice for applications with power densities of up to 25 kW per rack (with 50 kW heat exchanger door) and for dissipating residual heat in liquid cooling environments.
The first coolant distribution unit (CDU) from STULZ: CyberCool CMU
The CyberCool CMU is STULZ’s first pure liquid cooling product. The coolant distribution unit (CDU) is designed for both liquid cooling environments and hybrid environments, where air and liquid cooling are used in parallel.
A key feature of the CDU is that it separates the FWS (facility water system) and the TCS (technology cooling system) by means of a heat exchanger. This allows the temperature and flow of both circuits to be regulated independently by valves and pumps. In addition, this separation enables compliance with the stringent purity requirements for TCS water, and allows the use of fluids that do not damage servers in the event of leakage.
The CDU is available with a rated heat exchange of 345 to 1380 kW under standard system conditions, and copes with temperature windows from class ASHRAE W32 to ASHRAE W+. It is therefore suitable for use in combination with a chiller with Free Cooling function, for direct-to-chip and immersion cooling – and even for year-round Free Cooling, if the TCS temperature is appropriate.
What’s more, the achievable temperature ranges are an ideal basis for integrating waste heat recovery systems. And with the STULZ E² Controller, simple closed-loop control and connection of the CMU to a DCIM system are no problem either.
CDU as the central element for hybrid cooling solutions
Even air conditioning units, in-line air conditioning units and door cooling units that were previously used purely for air cooling can also be used in parallel with liquid cooling components. Moreover, air conditioning units such as the CyberAir 3 PRO can remove the 20 to 30 percent of residual heat originating from non liquid-cooled components, such as power supply units, for example. In-line air conditioning units such as our CyberRow systems can also discharge the residual heat from the air, but are situated directly between the racks, offering shorter and therefore more efficient air conduction routes. Alternatively, heat exchanger doors such as STULZ’s CyberRack system can be fitted to the back of the racks, removing residual heat directly from them. When heat exchanger doors are used, there’s no need to divide server rooms into hot and cold aisles, because the hot air is no longer discharged into the room.
To cool the facility water system, the CyberCool CMU is usually combined with a chiller with Free Cooling function, such as the STULZ CyberCool Explorer. This is able to work in three different modes, depending on the configuration: Free Cooling, Free Cooling in combination with compressor cooling (with infinitely variable control), or pure compressor cooling. At the ASHRAE W32 to ASHRAE W+ temperature ranges mentioned above, the chiller can make use of energy-saving Free Cooling mode almost all of the time in temperate zones. Of course, STULZ offers many other chillers for a large variety of applications, for a rated heat exchange from 40 to 1860 kW.
Complete liquid cooling solutions from a single source
With STULZ MODULAR, as well as providing the cooling solutions ourselves, STULZ is also your one-stop shop for fully pre-configured micro data centers and modular data centers. The modules are equipped with cooling (for example CyberCool Indoor Chiller, TelAir Shelter air conditioning unit, CyberCool CMU), power source (UPS, PDU) and Data Center Infrastructure Management (DCIM), so all the customer needs to do is add IT and network equipment. As well as the in-house components mentioned above, STULZ also uses components from partner companies such as Asperitas to equip these modules. Asperitas is a liquid cooling specialist that provides tank systems for immersion cooling which, in combination with CDUs, chillers and air conditioning units from STULZ, enable the complete cooling of a compact high-performance data center module with an IT capacity of up to 200 kW. STULZ Micro DC micro data centers are also available with liquid cooling for an IT capacity of up to 100 kW.
The liquid cooling product line is being expanded
With the CyberCool CMU, STULZ has laid the foundations for entry into the liquid cooling sector. As well as numerous products for air cooling – which is still the first choice in many application scenarios and is also constantly evolving – further liquid cooling products are set to enhance the STULZ portfolio for the long term in the high-performance computing sector. This way, STULZ’s ability to offer individual solutions for every kind of capacity will continue into the future.