A few days ago, I read a Nov 2006 White Paper (Doug Garday / Daniel Costello) on air-cooled high performance data centers. Especially case study 4 shows some numbers that seem to be unbelievable to me. As our company is planning data centers in germany since many years and we are always in search of contemporary knowledge, I would be glad if could give some comments to your floowing statement:
"We plan to use passive chimney cabinets, which work well with warmer supply air temperatures. Warming the 65º F supply air by 50º F as it passes through the cabinets will result in return air at 115º F. We may decide to mix this with an additional 19 percent bypass air (66,065 SCFM), tempering the return air to 108º F to match the capabilities of the RAH coils. "
WOW! This tells me you are operating with a delta-t of 27C (50F) at the IT devices! Relatively warm supply air (18,3C) will be heated to 46C in the cabinets. What kind of IT-equipment do you use? If I look at data sheets most servers have an operating temp range between 5C and 35/40C. So we try to operate with a 16C supply air and 26/28C return air.