5 min read

Liquid Cooling in Data Centers, why is it needed?

What is Liquid Cooling?

In theory, it is a simple cooling methodology, using liquid as the primary means for capturing and expelling heat created by IT load. Unfortunately, there are many misconceptions about the different technologies available, with a large portion of our industry believing there are only two types of Liquid Cooling:Immersion Cooling
IT equipment is submerged inside an electrically non-conductive liquid inside a tub that absorbs heat.Direct Chip Liquid Cooling (DCLC) 
Small hoses bring cool water to heat sinks or cold plates and circulate warmed water to a heat exchanger. Even though both technologies have merit, there are considerable downfalls. With immersion cooling there are significant setup costs, it does not capture 100% of the heat generated, which would mean you would require a secondary, supplementary cooling source, and this is the same with Direct Chip Level Cooling, which only captures between 60-80% of the heat.

Liquid Cooling in Data Centers, why is it needed?

Modern chips and processors are smaller than ever and are at the point that the manufacturing process has exhausted Moore’s Law.These modern chips and processors are compacted so tight it creates a significant heat load, which then means we need more efficient and sustainable cooling solutions, e.g., they need to absorb heat more efficiently than standard air cooling. This has led the Data Center industry to investigate Liquid Cooling in more depth.

So, is there an alternative technology?  

Yes, there is…… Rear Door Heat Exchangers (RDHx), or known also as Rear Door Coolers (RDC), is a proven liquid cooling technology, sometimes known as Air Assisted Liquid Cooling, which is designed to operate as a closed loop system.
In principle there are two main types of Rear Door Cooling methods, passive and active.
coil, with the resulting chilled air being expelled back into the room.
Similarly, with an ProActive Rear Door Cooler (RDC), ambient air is pulled into the rack by the IT equipment fans, however the resulting hot exhaust air is assisted by EC fans mounted within the proactive door and the air expelled over a heat exchanger,
transferring the heat into the liquid inside the coil, with the resulting chilled air being expelled back into the room at, or just below, the predetermined room ambient temperature.
In this way the ProActive Rear Door Cooler can control the whole room temperature environment, without supplementary cooling technology.


When the whole data center is taken into account, all liquid cooling solutions require air to assist in the data center cooling process, the ColdLogik solution integrates this as standard without the need for supplementary cooling equipment. There are many misleading industry articles, hopefully this document sets the record straight.

Challenges and Solutions


Bulk faced the following challenges:

  • How to design a solution for a colocation customer when specific IT technology, density or rack configuration is not known.
  • How to cater for the current GPU trend requiring 40-50kW+ per rack, while also considering future tech upgrades that could scale to even higher densities including Direct Liquid Cooling (DLC).
  • Find a flexible solution that allows its customer the option to select and bring in their own racks of different sizes and manufacturers.
  • Maximise operational efficiency through optimised airflow and heat rejection.
  • Reduce time for white space fit out and customer deployment by pre-installing and testing all cooling components.


The ColdLogik solution:

  • Energy Efficiency Ratio (EER) of over 100 at maximum capacity.
  • Average 15% reclaimed power for Compute by comparison to traditional cooling.
  • Potential Cooling PUE available of 1.035 with RDC.
  • Over 50,000 trees worth of carbon saved per 1MW ColdLogik deployment.
  • Adaptive Intelligence that controls the whole room temperature.
  • Higher water temperatures reduce the need for mechanical cooling, whilst maintaining ASHRAE A1 temperatures.


Data Center Products 

that Exceed Expectations

Discover the High Performing Data Center products, including ColdLogik Rear Door Coolers – RDHx, ColdLogik InRow Cooler, ColdLogik & EDGE LX Plant.
Rear Door Heat Exchanger

CL21 Passive Rear Door Heat Exchanger

The CL21 Passive RDHx offers high-performance cooling at zero-operational cost.

ColdLogik CDU

Efficiency, reliability, and innovation define our CDU.
Server Cabinet

USpace - 4210 Cabinet

Cost-effective and versatile Rack, adapts to diverse applications, offering ease and flexibility.
InRow Coolers

CL80 600W InRow Cooler

Precision cooling solutions for aisle containment, ensuring optimal performance.
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Server Cabinet

USpace - 5210 Cabinet

High-density design with flexible configuration for evolving IT environments.
InRow Coolers

CL80 300W InRow Cooler

The highest cooling capacity available in a footprint of a chilled water InRow.


Data Center Solutions
that Exceed Expectations

Get in touch with us at USystems Ltd to join the journey towards more efficient and sustainable data centers. Our leading and innovative technologies are designed to help you use less energy and reduce your carbon footprint on a global scale. Contact us now to explore how we can work together for a greener future.
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