Cooling of server electronics: A design review of existing technology

• Review heat transfer/flow parameters from studies on server cooling technologies.
• Perform direct quantitative comparison between cooling technologies.
• Identify heat transfer limitations, power requirements, etc.
• Summarize industry implementations of each cooling solution from a design perspective.
• Identify the capacity of cooling solution relative to heat loads expected by 2020.

This review quantitatively examines and compares the heat transfer characteristics of several cooling technologies with potential application in the server electronics industry. Strategies that have been examined include traditional air cooling, single and two-phase indirect liquid cooling, heat pipes, pool boiling, spray cooling, and jet impingement. The characteristics that have been examined include heat flux values, coolant temperatures, and coolant flowrates; which serve as indicators of the heat transfer limitations and power requirements of each cooling solution. A direct comparison against anticipated server heat loads has shown that some form of liquid cooling is necessary in high performance computing applications; where individual processor heat loads are expected to reach 300 W by the year 2020. While in the case of general purpose computing, where individual processor heat loads are expected to reach 190 W, air cooling remains a viable option; although other factors such as operating costs, chip reliability, and waste heat recovery may still encourage the use of liquid cooling.