Flow network analysis of the IBM Power 775 supercomputer Water Cooling System

In 2011 IBM announced the Power 775 Supercomputing node/system which, for the time, was a monumental leap forward in computing performance and energy efficiency. The system was designed from the start with water cooling in mind. The result: a system with greater than 95% of its heat load conducted directly to water and a system that, together with a rear door heat exchanger, removes 100% of its heat load to water with no requirement for room air conditioning. In addition to direct water cooling the processor, the memory, power conversion, and I/O electronics also conduct their heat directly to water. Also included within the framework of the system is a disk storage unit (i.e. disc enclosure) containing an interboard air-to-water heat exchanger. A detailed flow network analysis was undertaken to assure adequate flow to all components in the system while minimizing pump power consumption for a wide range of system configurations. The analysis was validated by both early development experimentation as well as final system verification. The network analysis could therefore be used to establish pump speed tables for normal and abnormal modes of operation. This paper will outline the assumptions and methodology associated with the flow network analysis and demonstrates how the analysis was used for the design and operation of the water cooling system.