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HVAC stands for heating, ventilation, and air conditioning. In large data centers, HVAC systems regulate the ambient environment (temperature, humidity, airflow, and air filtering). This system must be planned carefully, operated alongside other data center equipment like cabling, data storage, computer hardware, fire protection, physical security systems, and power.
Therefore, in data center planning, a crucial step includes selecting an HVAC contractor and following all the guidelines and strategies for efficient cooling.
For details regarding the guidelines for data center design, please visit: Data Center Design Standards and Guidelines You Must Follow
Nearly all computer hardware comes with environmental guidelines and requirements that include humidity and temperature ranges. A separate space called a plenum is allocated to allow air circulation adhering to the environmental guidelines. This facilitates air circulation for HVAC and cabling, mainly between the structural and drop-down ceiling or under a raised floor.
Data centers house loads of computer servers that provide and facilitate internet and networking-based services for the users. They vary vastly in size, ranging from small single-room facilities to enormous internet giants like Google and Facebook.
With more and more facilities being developed and designed, they must run as efficiently as possible. In addition, all the internet and networking facility users rely on these data centers for internet and remote services to store, access, and stream data.
As the data centers operate 24/7, they consume lots of electricity, which is used to power the servers to process the tons of data being collected. This generates much heat, which needs to be eliminated since it causes the electrical components and hardware to overheat and fail, or even cause fire, costing a lot of working capital for the downtime.
Here, we will focus on data center HVAC, emphasizing the cooling systems used and how the technology works. We shall compare how the different cooling strategies work and optimize their efficiency, especially with Computer Fluid Dynamics or CFD.
A combination of raised flooring and computer room air conditioner (CRAC) or computer room air handler (CRAH) infrastructure are employed in traditional data center cooling approaches.
In the first part, we’ll cover the non-data hall areas, including where the staff, security guards, engineers, and technicians are located. These cover the offices, toilets, workshops, and rest areas.
These areas shall be served with a separate mechanical ventilation system and will either use an air handling unit or a rooftop unit to allocate the airflow to suit the needs of the staff and might use a separate split unit or VRF system for regulating the temperature in these areas.
Coming to the server rooms, one of the most common methods of cooling is to place the server racks on a raised floor and then use Computer Room Air Conditioners or CRAC units to distribute cool air to the individual server racks.
The Computer Room Air Conditioners (CRAC) have heat exchangers inbuilt, connected to refrigeration units or chilled water systems to remove the heat of the respective server racks.
In addition, some equipment can humidify or dehumidify, which plays an important role in determining the control of static electricity in the air. Finally, they have filters inside to remove and clean the dirt and dust seeping in as a fan circulates and distributes the air.
In order to optimize the efficiency of CRAC systems, energy-efficient filters, EC or electronically controlled fans, and pressure sensors in the floor void should be used to accurately and precisely control the supply rate.
Also, placing temperature sensors on the intake grills is recommended to maintain the supply temperature from the CRAC units and match the actual intake.
The cool air from the air conditioners in the CRAC unit is forced into the void under the floor, and small holes or grills are installed to allow the air to exit strategically through the required exit points.
The stand-down below heats up gradually by absorbing it and slowly rises. The CRAC units efficiently suck up the warm air back into their ducts to be reconditioned.
Previously, in traditional models, the servers in the data center were faced in separate directions. Soon, engineers realized that the system was inefficient because the fresh cool air from the CRAC units was mixing up with the warm air of the racks. This caused intermixing of the temperatures leading to greater energy consumption and higher failure rates of these units.
To combat the problem, engineers designed the racks facing the same direction so that the air of different temperatures was separated and optimized.
The following strategy used is the method of using Hot and Cold aisles. This is a great improvement from the old traditional designs because it efficiently separates the fresh cold air stream from the conditioners with the hot discharge air from the racks.
The cold air rises from the grills on the floors and is maneuvered through the server racks, and all the discharged hot air is collected into the ducts and eliminated into the CRAC units for further cooling.
This ensures the servers only receive fresh air and the CRAC units get the hot discharge air, increasing the temperature differential across the heat exchangers and improving the facility’s efficiency.
Though the system seems perfect, various problems can arise, causing the intermixing of Hot and Cold air streams. They may include:
There could be leakages on the cutouts or grills on the floor, which means that the hot air can mix with the cold air in the hot aisle.
Floor grills close to the CRAC units could result in cold air circulating back to the CRAC unit and intermixing with the return stream of hot air.
Server racks can have broad gaps that make the air recirculate around the racks and can be resolved by introducing blanking plates.
If more cold air is pushed than required, it could flow over the units and mix with the returning discharge.
You can use a much better and improved design and is very popular in growing data centers in modern times is to use a physical barrier to separate the two air streams.
There are a couple of methods of achieving this. First, the facilities can use a barrier around the server racks and then contain hot or cold air.
Cold air containment is used in various data centers and is growing in demand recently. This is because it is cheaper, and the payback is rapid. The cold air from the conditioners fills the cold aisles, and the hot air from the racks discharge fills the rest of the server room, with the CRAC units pulling it back in for reconditioning.
The contemporary competitor is the hot air containment method, best suited to growing centers due to its higher costs. According to this strategy, the cold air fills the room, and the hot air is pushed into a separate void present in the ceiling.
The intake method of the CRAC units is also separated into the ceiling to pull the hot air in for reconditioning. This process is more efficient and provides better performance, with a slight cooling buffer in failure.
Using CFD or Computer Fluid Dynamics, we can quickly and accurately compare the performance of different setups of the server room facilities. At Mechartes, we use advanced simulations using revolutionary cloud-based CFD and FEA engineering tools to recreate the process.
Mechartes focus on providing accurate simulation results with a professional approach using advanced engineering tools. We provide Data Center Validation Services, including the pre-design stage, design stage, and construction stage.
Looking for CFD Analysis in HVAC Systems in Saudi Arabia? Click here.
Our specialty includes Data Center Architecture and Engineering. The different stages we design, and the specific technologies we use are:
Pre-Design Stage: We use External Flow CFD analysis for the chiller and generator yards present in the Data Center sites. We carefully assess the wind directions and weather conditions to judge the perfect placement of the chiller and generator units.
Design Stage: We use CFD Analysis to validate and optimize the HVAC (Heating, Ventilation, and Air Conditioning) design of the following areas per specific project requirements: Data Hall, Generator room, and DRUPS room.
Construction Stage: Stress analysis is used to analyze the existing piping networks as it helps diagnose the design’s compatibility with its weight, pressure, and thermal stress. We provide support and design suggestions for the most effective design based on the detailed stress analysis report.
For expert consultation on designing or expanding your data center, visit Mechartes and get the best guidance adhering to all the common problems beginners face, all the way up to advanced tier 3 designs of data centers for mega users.
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