The analysis assumes 28[degrees]F [DELTA]T for IRAH (95[degrees]F EAT, 67[degrees]F LAT) and 19[degrees]F [DELTA]T for CRAH (95[degrees]F EAT, 67[degrees]F LAT) so the CRAH requires 50% more cfm in the analysis.
The analysis fails to recognize that IRAH have higher pump energy.
Currently, one manufacturer pretty much owns the market for chilled water IRAH in the US.
IRAH will not require a raised floor or plenum return system that offsets the higher capital cost.
There are typically three to five times as many IRAH as CRAH for any given application.
Authors: To look at the whole picture, the IRAH will not require the raised flooring or return plenum as the CRAH, offsetting any additional piping work.
Chilled water IRAH requires that chilled water pipes run under or over the racks.
IRAH only serve a single hot aisle, while CRAH typically serve the entire data center.
IRAH can achieve redundancy at the row level by adding one to two units per hot aisle (can vary by airflow and density requirements).