Data Centre Cooling - Temperature

Evaporative cooling is a very simple method of cooling air without using refrigerants.  The CREC is a direct evaporative cooler, using wetted filter pads to cool air by bringing it into contact with water.  Water evaporates into the air stream and cools it.  The amount of cooling is dependent upon the temperature and relative humidity of the air.  In the UK the maximum theoretical air off temperature is 22°C.  In practice the actual temperatures achieved using evaporative coolers in UK data centres can approach 24°C on the very warmest days.  This allows full compliance with ASHRAE temperature standards.

Since the ambient temperature is low for much of the time in the UK it is possible, for no additional operating cost, to cool at the lower end of the ASHRAE standards with 18.5°C being a typical set point.  This permits a more comfortable environment for operators and also reduces temperature related failures.  ASHRAE claims typical temperature failure rates to be over 25% less at 18°C compared with 25°C.

Experience has shown that it is low temperatures which can cause the greatest problems in a data centre using fresh air systems.  The attemperation of air on very cold days is essential to provide a constant flow and temperature compliant conditions.  Some servers automatically shut down when low temperatures are detected.  The CREC system can achieve +/- 0.5°C temperature accuracy.

Data Centre cooling - The Psychrometric chart

Data Centre cooling - The Psychrometric chart

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