Technical rooms – Data Center.

Using CFD for thermal optimisation

Why carry out a CFD study?

In the world of data centers, thermal management holds a central place. Usually, hot and cold aisles are arranged in the halls to optimise the cooling of the servers and equipment. However, when it comes to the technical rooms, the situation is quite different: each installation is unique, with its own constraints and configurations, which makes standardised cooling solutions often unsuitable.

In this context, expertise in CFD (Computational Fluid Dynamics) plays a key role. In the absence of established measurements and off-the-shelf solutions, it is essential to turn to advanced modelling tools to understand and optimise air circulation, heat dissipation and temperature distribution. Using CFD, an in-depth analysis of the infrastructures is carried out in order to identify the hot zones, optimise the airflows and design cooling solutions suited to these technical rooms.

3D modelling process

To build the 3D model of a technical room for the CFD study, the approach relies both on the room plans and on site visits. First, the detailed architectural plans of the room made it possible to recover the dimensions and the layout of the equipment. Then, during the site visit, more thorough observations and precise measurements were carried out, and specific details such as the cooling systems, the ventilation grilles and the obstacles were recorded.

Using 3D modelling software, geometric models of the rooms were created, incorporating the equipment and the obstacles of the room while respecting their real position. Finally, by assigning the appropriate physical properties to each element of the model (thermal conductivity of the materials, heat releases of the machines, performance of the air-conditioning systems), the CFD studies could be carried out.

Simulation results

Detection of the thermal anomalies and short-circuiting

During our simulations on the existing configuration of the technical rooms, excessively high temperatures were observed at the fresh-air intakes of the systems. These high temperatures are caused mainly by short-circuiting phenomena, where the hot air is recycled instead of being removed efficiently.

In addition, the presence of hot spots, zones where heat dissipation is insufficient, was identified, which can lead to risks of equipment overheating. A new design is then necessary to optimise air circulation, avoid the short-circuiting phenomena and improve thermal dissipation.

Bespoke solutions

New designs suited to each room were proposed to avoid the short-circuiting phenomenon and reduce the excessive temperatures:

• STS

  Ducting of the heat releases to better channel and remove the heat.

• UPS

  Full enclosure between the upper and lower parts to compartmentalise the hot and cold air masses.

• TR

  Raising of the CRAH intakes for better capture of the heat-laden air.

These new designs were submitted to advanced CFD simulations to assess their effectiveness. The results are very encouraging: they clearly show that the new designs make it possible to avoid the short-circuiting phenomenon and to reduce the temperatures at the fresh-air intakes of the systems. The temperatures could be lowered by 5 °C, which greatly contributes to guaranteeing optimal operating conditions and to reducing the risks of overheating in the technical rooms of the data center.

Redundancy study: CRAH shut down

A meticulous redundancy analysis was carried out in the technical rooms in order to ensure unrivalled reliability of the cooling systems. For this, two CRAH units are installed in each room, operating in parallel for optimal operational redundancy. This approach makes it possible to maintain sufficient cooling capacity even in the event of a failure of one of the units.

In order to validate the effectiveness of this redundancy, detailed simulations were carried out considering the deactivation of one CRAH unit. The results showed that even with one CRAH shut down, the temperature in the technical rooms remains within a suitable range, with no risk of overheating. This demonstration highlights the effectiveness of the redundancy put in place.

At EOLIOS, the crucial importance of redundancy in critical environments such as data centers is always taken into account. Expertise in CFD simulation makes it possible to design robust and reliable cooling solutions, thereby guaranteeing continuous availability of the equipment even in the event of a failure of one unit.