The Cray supercomputing cabinets are designed in serial from a cooling perspective. On the left hand side you can see an air pre-conditioning unit on the end of the stack, followed by a thin red cabinet that hosts blowers, the larger open red door that houses a rack of blade servers (as does the next cabinet), before another fan unit (thin red door), and so forth.

The pre-conditioning unit controls the temperature of the air being sucked into the supercomputer on the off-chance there has been a heat event in the facility while the fans/blowers project that air onto the racks. The racks are in turn water-cooled by a 22-degree line of groundwater drawn up from an aquifer underneath the facility.

The final exhaust at the other end should - if all goes to plan - return air back into the data centre at neutral (the same temperature it came in at). Arguably, in cooler climes a machine like this could run in a data centre using free cooling and avoid the use of chillers altogether.

As it is Pawsey is saving millions on water and quite a bit on power, but they have still installed chillers in this room as a precaution. Perth is a pretty hot place, after all, and there are other machines in the same room that don't run quite as efficiently.