Direct Liquid Cooling (DLC) uses the exceptional thermal conductivity of liquid to provide dense, concentrated cooling to targeted areas. By using DLC and warm water, the dependence on fans and expensive air handling systems is drastically reduced. This results in much higher rack density, overall reduced power use and significantly higher performance potential.



A key component of the Passive and Active Coldplate Loops, CoolIT Systems’ patented Split-Flow Coldplates are solid copper components which deliver superior performance for today’s high thermal density processors.

The Split-Flow design uses microchannel architecture to minimize pressure drop, maximize coolant flow, and direct the coolest liquid to the hottest area of the processor first. Starting at only 2.4mm in height, Coldplates are easily integrated into extremely compact, low-profile blade architectures, and provide optimal performance.

Custom Coldplate designs are available.


To provide customers with product flexibility when integrating liquid cooling into new or existing data center facilities, CoolIT’s Rack DLC platform utilizes a three module “building block” approach which includes Passive Coldplate Loops, Rack Manifolds and Coolant Distribution Units.


Direct Cooling Liquid (DLC)

What is Direct Contact Liquid Cooling (DLC)?
DLC is a technology developed and patented by CoolIT Systems that uses warm liquid rather than cold air to dissipate heat from computer and server components. By capturing component heat in a liquid path, DLC allows for higher component performance and reliability, higher densities and decreased data center operating expenses through a decrease, or elimination of, chillers and CRACs.

Why choose liquid cooling instead of traditional air cooling?
By integrating DLC, dependence on expensive air conditioning and air handling systems is dramatically reduced, enabling more servers per rack, low power usage and access to significantly higher performance potential. Rack DLC integration translates into an effective and scalable cooling strategy which significantly reduces OPEX.

What is a Closed-Loop DLC System?
Closed-Loop DLC Solutions are cooling systems designed by CoolIT that exist entirely within the Desktop or Server. The sealed liquid loops ship charged with coolant, and installation is comparable to that of a standard heat sink. CoolIT has many types of Closed-Loop systems for desktops and servers (1U, 2U, and custom rack-mount).

What is CoolIT Systems Rack DLC?
CoolIT’s Rack DLC platform is a modular, rack-based, advanced cooling solution that allows for dramatic increases in rack densities, component performance and power efficiencies. Rack DLC is compatible with new and existing data centers and can work with or without facility water connection.

What does Rack DLC do for high performance computing (HPC)?
At the rack and server level, Rack DLC solutions allow for major increases in density while also allowing processors to run more cleanly at lower temperatures and utilizing fewer in-server fans. At the facility or facility’s infrastructure level, Rack DLC allows for 80% or greater reduction in air cooling infrastructure using ASHRAE W3-W5 water to cool the processor load.

What is the acceptable facility water temperature for Rack DLC?
The acceptable liquid temperatures are ASHRAE W2 to W5 (W4= 2°C-45°C , W5> 45°C).

What servers and racks are compatible with CoolIT Rack DLC?
CoolIT Rack DLC supports any server or rack model. Our low profile server modules are ideal for high density servers and easily accommodate any existing products.


What are the three modules that make a Rack DCLC solution?
They are: Passive Coldplate Loops, Rack Manifolds and Coolant Distribution Units (CHx or AHx).

What is the difference between CoolIT’s Rack DCLC CHx and AHx Coolant Distribution Units?
CHx: Liquid-to-liquid CDU which uses facility water to capture and remove component heat from the compute environment

  • CHx650: 650kW of processor load with ASHRAE W4 or W5 water (manages network of 5 to 20 racks)
  • CHx80: 80kW of processor load with ASHRAE W3-W5 water (manages a single rack)
  • CHx40:  40kW of processor load with ASHRAE W4 or W5 water (manages a single rack)

AHx: The liquid-to-air CDU platform requires no facility water to operate, sits on top of the rack for which multiple designs available such as: hot aisle, cold aisle, chimney, etc.

  • AHx20: Manages 20kW of processor load
  • AHx10: Manages between 7-10kW of processor load depending on configuration
  • AHx2: Factory test bench tool that manages up to 4 nodes

Service & Maintenance

Can users monitor and manage their Rack DCLC systems?
Yes, all Rack DCLC solutions ship with a management system that can be accessed remotely (SNMP and web server) and at the rack level.

Is it possible to disconnect any of the system modules in case of an emergency?
Yes, servers are hot-swappable with the Rack DCLC system. Dry-break quick disconnects allow removal of any part of the system (Passive Coldplate Loops, Rack Manifolds or CDUs) as needed without disrupting the cooling functionality of the remaining servers. This feature is particularly useful in case of an emergency or if users need to isolate any one area.

Does CoolIT provide partners and customers with support services and warranty?
Yes, CoolIT does provide support services and warranty to its partners and customers as required.

Does CoolIT have ISO Certification?
Yes, CoolIT is ISO 9001 certified.


Is liquid cooling going to increase my server costs?
The initial cost of integrating liquid cooling is quickly offset by several factors:

  • A high-density solution requires less standard data center equipment (racks, switches, raised-floor, etc.), which lowers overall capital expenses
  • Rack DCLC enables a 25-30% decrease in operating expenses, thanks to reduced chilled water requirements
  • The average ROI for Rack DCLC solutions is 0-6 months

What is the difference between Direct Contact Liquid Cooling and immersion cooling?

CoolIT Systems Rack DCLCTM Single Phase Immersion Cooling
$0.50 – $0.75 per watt (can go as low as $0.35) $1.05 per watt (*data from company website)
Allows for servers to be unplugged and maintained as per normal service protocols Servers must drip-dry and be cleaned prior to service
Uses only the highest quality components and materials, stringent manufacturing methods and extensive testing to ensure a long lifecycle Rubbers and plastic slowly leach into mineral oil which changes the heat transfer properties and reduces the lifecycle of components
Easily integrates into any data center environment using standard rack and server architecture Expensive to retrofit, requiring the replacement of all HDD with SSD (or adjustments to HDDD) and non-standard equipment, as existing racks must be discarded
Increases density with fully populated vertical racks which make the most of available square footage Mineral oil tubs do not maximize the use of space for traditional data rooms, resulting in far less density per square foot

STULZ Partnership

What geographic area will the STULZ / CoolIT partnership cover?
This is a global relationship. STULZ has a presence in 140 countries and on every continent.

Is this an exclusive relationship?
No. This relationship is not exclusive for either party and CoolIT Systems remains an independent company. Providing the best, customer-focused solutions will always be CoolIT Systems’ goal, regardless of the technology provider.

What is a “Chip-to-Atmosphere” solution?
Combining the expertise of STULZ and CoolIT Systems creates a unique partnership which provides customers with the world’s first “Chip-to-Atmosphere” solution. For customers, this represents a single provider of an integrated solution managing the entire heat cycle from the processor and IT equipment through to moving the heat out of the building. At this point, customers can choose to exhaust heat into the atmosphere or recycle the heat. Regardless of whether the IT is cooled by liquid, air, or a combination of both, the STULZ/CoolIT Systems partnership will deliver the solution for all data center cooling needs.

Will STULZ be doing the Service & Support globally for CoolIT Systems?
Yes. The service capabilities of STULZ will strengthen and expand the existing CoolIT Systems service organization to provide trained technicians in 140 countries. STULZ will also provide facilities to stock and forward repair parts to ensure cus-tomers needing replacement parts receive timely shipments, regardless of their data center location. These additional capa-bilities will be rolled-out over time.

Will STULZ be doing the installations globally for CoolIT Systems?
STULZ is a fully qualified partner and able to perform installations of CoolIT Systems technology around the world. STULZ technicians will concentrate on the liquid cooling infrastructure as much of the CoolIT Systems server technology is installed by the OEM at its factory, or by System Integrators.

Will STULZ be manufacturing for CoolIT Systems?
Yes. In time, STULZ will manufacture or assemble certain components for CoolIT Systems. This will be primarily driven by cost efficiencies resulting from scale or geographic advantages. CoolIT Systems will leverage STULZ’ manufacturing facilities across five continents to create cost-effective solutions for customers in their respective regions.

Who should we contact if we have questions?
Contact CoolIT Systems at We will forward your information request on to the appropriate person at CoolIT Systems or STULZ.


View our industry-leading collaborations with publicly disclosed customers.


Whether you own and operate a data center, or are an OEM or an HPC enthusiast, CoolIT has the right liquid cooling solution to fit your needs.