By Michael Young (Pr.Eng)
It’s enough cooling – but what of bad air distribution?
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Michael Young is a trainer, coach and a pre-sales engineer in the HVAC industry. He graduated from the University of the Witwatersrand in the field of Mechanical Engineering (B.Sc Mech Eng) in 2008 and qualified as a Professional Engineer (Pr.Eng) in 2013. Michael is passionate about promoting knowledge and helping other young engineers grow within the industry through his training workshops and coaching sessions. |
Excessive heat can damage components on IT servers – and many servers contain safety devices that detect high temperatures and shut down the equipment before permanent damage is caused.
For IT equipment to be cooled, air enters a server rack through the front face and hot air exits from the rear face of the air-cooled racks.
In this type of server rack, air is the cooling medium that will ensure that the IT equipment continues to function. Should the cold air not reach the rack, the IT equipment can shut down due to bad air distribution rather than insufficient cooling.
So, what does this mean? A cooling unit will change a certain volume of air from one condition to a different condition. It is the change of the air condition (temperature and humidity from one state to another state) that results in a cooling capacity.
So here is an example. Imagine we trap one litre of air in a soda bottle. Now we want to change the temperature of this trapped air from 30°C to 20°C. To do this, we will need to cool the air by a certain amount.
Now this is where air distribution comes into play. If you took this soda bottle, placed it over your face, removed the lid and squashed all the air out of the bottle. What would you feel? You would feel that litre of cool air rush past your face and you would feel pretty cool right? Now what would happen if you took the same bottle, stood 20cm away and did the same thing. What would you feel? Would you agree that you wouldn’t feel so cold?
The reason why you don’t feel so cold is that the air that leaves the bottle goes everywhere. Some of it goes to other parts of the room while other parts go onto your face. Even if we cooled all that air to a lower temperature, you may still not feel as cool as having the bottle directly near your face since you are short of airflow and not cooling capacity.
To make you cold when the bottle is a distance away from your face you either need to have more air available or you need to direct all the air that leaves the bottle onto your face. This is the problem that some data centres face. The cold air that is meant to be directed straight onto the servers is blown all over the place as the cooling units can be many metres away from the racks.
When this starts to happen, the data centre is experiencing an airflow issue and not a cooling issue as the correct amount of air is being conditioned but this cold air is not being distributed to the server racks in the correct manner.
So how does one distribute the air in the correct manner?
Find out in our next publication.
Wishing you a successful month ahead.
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