Cooling Trends & Data Centers by “Engr. Zohaib Ilyas”

Data centers comprise servers, storage systems, and networking equipment, primarily designed for processing and storing large volumes of data, which generates significant heat due to high-density computing. Therefore, effective cooling is critical for optimal equipment performance and reliability. Insufficient cooling can lead to overheating, resulting in costly downtime and potential data loss. The layout and configuration of data center rooms are essential for maintaining optimal temperatures and humidity levels, maximizing airflow, and minimizing hotspots.
Implementing efficient cooling strategies not only enhances energy efficiency but also prevents performance degradation, improves system reliability, and reduces energy costs. For data centers, a temperature range of 18°C to 27°C (64°F to 80°F) is recommended, with 20°C to 22°C (68°F to 72°F) considered optimal. Relative humidity should be kept between 45% and 60%; levels below 20% can cause static electricity, while levels above 80% can lead to condensation and potential equipment damage.
Traditional cooling methods include direct expansion and chilled water-based precision cooling units, such as Computer Room Air Conditioners (CRAC), Computer Room Air Handlers (CRAH), in-row cooling units, and in-rack cooling units. To optimize efficiency, these systems are often configured with raised floors, plenum designs, aisle layouts, and containment strategies.
Currently, cooling systems are the second largest consumers of power in data centers, following essential IT loads. As digital inclusion expands and the demand for high-density servers grows, the need for effective heat rejection increases, leading to higher per-rack densities. In this context, liquid cooling is gaining traction as an efficient solution.
Liquid cooling methods include direct on-chip cooling and immersion cooling.
On-chip cooling utilizes direct chip cooling cold plates configured for individual server loops, featuring quick disconnect fittings and leak-proof tubing connected to dry break couplings on manifolds. These systems efficiently capture heat from CPUs at (distilled water with additives) ASHRAE W3/W4 warm water inlet temperatures, maintaining optimal temperatures for overclocked processors. Cold plates can also transfer heat from other components, such as VRMs and memory.
The liquid distribution manifold serves as a bridge between the coolant distribution and servers, incorporating a Coolant Distribution Unit (CDU) with controlled immersion pumps for a closed-loop server cooling system. This setup requires only ASHRAE W3/W4 warm water and effectively exchanges heat with external loop of conventional cooling by dry cooler, cooling tower or chiller, addressing the cooling needs of power-dense racks.
Immersion cooling is as simple as submerging your server in a bath of non-conductive liquid, allowing heat generated by the components to transfer to the fluid. This can be cooled using either a single-phase or two-phase method. The liquid is fully biodegradable, is about 80% lighter than water and has twice the viscosity. It is non-conductive up to 60,000 volts and can handle over 5,000 amps across a 2mm gap. This capability enhances space utilization by allowing enclosure-free servers to be placed closely together.
Single phase immersion cooling is being done by circulating the coolant which is a dielectric liquid. The heat from submerged server in coolant bath tank is transferred to liquid which then sent to coolant distribution unit (CDU) using coolant pump, this CDU exchanges the heat with external loop of conventional cooling by dry cooler, cooling tower or chiller.
Two-phase immersion cooling is an innovative technology for data centers. In this system, electronic components are submerged in a dielectric heat transfer liquid, which conducts heat more effectively than air, water, or oil. The fluid has a low boiling point of 56°C (compared to water’s 100°C), allowing it to boil on the surfaces of heat-generating components. The rising vapor naturally facilitates heat transfer and exchanges to condenser running above liquid tank.
Two-phase immersion cooling liquids are clean, environmentally friendly, and non-flammable. This system eliminates the need for pumps and jets, as cooling occurs passively through evaporation, requiring no additional energy. This simplicity removes the need for conventional cooling hardware, enhancing overall cooling efficiency and significantly reducing energy consumption compared to traditional air, water, or oil cooling methods.
Immersion cooling technology enables highly efficient cooling, contributing to a low carbon footprint and achieving an ultra-low Power Usage Effectiveness (PUE) of 1.03 & below. n