Data Center

Data centers, simply put, are computer server rooms which provide networking and internet based services. They range in size from a small single room serving a single organization and scale all the way up to enormous internet giants such as Google and Facebook.

More and more data centers are opening each year as we use and rely increasingly on the internet and remote services to store, access and stream our data. With this growing trend it’s important that the buildings run efficiently as possible.

As the data centers are operational 24/7 they can consume vast amount of electricity and as this electricity is used to power the servers and process all the data, it generates a lot of heat. This heat needs to be removed otherwise the electrical components will overheat and fail or even catch fire.

The energy consumption for a typical data center might be split with around ~50% being used by the IT equipment, 35% on cooling and HVAC, 10% on Electrical Infrastructure & Support and around 5% on Lighting. The electrical demand for data centers really varies from just a few kW up into the megawatts depending on the size and location.

Types of Units used in a data center

One of the most common methods currently used is to place the server racks onto a raised floor and then use Computer Room Air Conditioners or CRAC units to distribute conditioned air to the server racks.

CCU/CRAC units

The CRAC units have heat exchangers inside which are connected to refrigeration units or chilled water systems to remove the heat of the server racks. Some can also humidify or dehumidify the air that’s important in order to control the static electricity in the air, they have filters inside to remove dust from the room as well as a fan to circulate and distribute the air. For extra efficiency the CRAC units should use energy efficient filters, EC or electronically controlled fans and pressure sensors in the floor void to precisely control the supply rate, placing temperature sensors on the intake grills on the server rack is recommended to control the supply temperature from the CRAC units as this matches the actual intake.

Raised floor

The conditioned cold air will be forced by a fan in the CRAC unit into the void under the floor and small holes or grills in the floor tiles will allow the air to leave the void in strategic places. This air will collect the heat and rise up towards the ceiling. The CRAC units then suck this warm air back into the unit to be reconditioned. In the early days the server racks were positioned facing different ways and engineers soon realized this was very inefficient because the fresh cold air was just mixing with the warm discharge air off the servers and this meant that the servers were receiving different air temperatures, some hot some cold and this lead to higher energy consumption and a high failure rate of servers.

To combat this the servers were positioned so that all the server racks were facing the same way. This was a slightly improved strategy but quite often some of the discharge air was being pulled into the intake of the server racks sitting behind it which leads to mixing and an increased air temperature.

Hot and cold aisles

Hot and cold aisles is a strategy which is still very common today. This is a great improvement on the previous designs because it separates the fresh cold air stream from the hot discharge air. The cold air rises out of the floor grilles and is pulled through the servers, all the discharged hot air collects into the hot aisle and rises up towards the ceiling where it is then pulled back into the CRAC unit. This means the servers receive only fresh cold air and the CRAC units receive the hot discharge air which increases the temperature differential across the CRAC unit’s heat exchanger and that will improve the efficiency of the machine.

This is not perfect however because there will still be some mixing of the hot and cold air streams due to the following reasons:

1. Cut outs in the floor can result in air leaks, this means cold air can leak into the hot aisle.

2. Floor grills too close to the CRAC units result in cold air recirculating straight back to the CRAC unit and mix with the return stream.

3. Gaps between the servers can result in air recirculating around inside the server rack, this can easily be solved by installing blanking plates.

4. If more cold air is supplied than needed it will flow over the untis and mix with the discharge

5. If insufficient cold air is supplied then warm discharge will be pulled over the top or around the side of the server and into the cold aisle and will mix with the stream.

A much improved design and one that is very popular currently for both new and existing data centers is to use a physical barrier to separate the two air streams. There are a couple of ways to do this, we can use a barrier around the server rack and then contain either the hot air or the cold air.

Cold air containment

Cold air containment is a very popular choice for existing data centers, because it is easy and cheap to implement which means the payback is quick. The cold air fills the cold aisle and then the hot discharge fills the rest of the room with the CRAC units pulling this in for reconditioning. If you have an existing data center that isn’t currently using this method then I recommend you contact us for a quotation ASAP!

Hot aisle containment

The other containment strategy in use is the hot aisle containment, this is best suited to new buildings as it costs more to install. In this strategy the cold air fills the room and the hot discharge air is pushed into another void within the ceiling. The intake for the CRAC unit is also ducted into the ceiling to pull this hot air out for reconditioning. The hot aisle containment provides superior performance and also allows a slight buffer of cooling should the power or cooling system fail.

We install all the systems described above at affordable prices,calls for more information or place you quotation request today,we will be happy to help.