Bell
A CRAC and CRAH carry out the exact same function and still cool 90% of all data centres globally.
The difference between the two is simple. A CRAC unit is cooled by refrigerant and a CRAH is cooled by water. CRAC units usually have a single outside condensor for each CRAC unit where as a CRAH unit will get its chilled water form a chilleed water circuit from a bank of chillers.
Generally we see CRAC units in smaller data centres or in data centre in locations with extremely high temperatures. But even refrigerants have their maximum operating temperatures for examplle R22 can operate up to about 46degC but as I have experienced in some of the middle east this is sometimes not enough as some locations go up to 52degC. Not a nice location to have to work
So yes they still do play a major role in the provision of cooling in the data centre. For data centres with raised floors thses types of units deliver the cold air into the floor void.
Vincent
|