ABSTRACT
This paper proposed and introduced an innovative concept of step-like server placement in data centers (DCs), replacing the traditional servers placed on the same vertical plane with step-like server placement. The studied simplified DC model was established based on an actual operating DC. The feasibility and reliability of the simplified model was validated by on-site experimental results. This paper is analyzed two scenarios: the effects of horizontal spacings (0, 0.01, 0.02, 0.03, and 0.04 m) between adjacent servers and with the effect of different supply air temperatures (SATs) (22.5, 23, 23.5, and 24°C) on the rack hotspot. The results show that step-like server placement can effectively enhance the thermal distribution, while the optimum thermal distribution is achieved with the spacing of 0.01 m in case 2. Under this circumstance, the rack hotspot reduced by 2.5°C, while case 2 is selected for further analysis in scenario 2. In scenario 2, the thermal environment in cases 6–8 are totally better than that in case 1 in terms of rack hotspot and temperature distribution. Although there appears another moderate heat accumulation at the top-side, the overall thermal distribution in the case with SAT of 24°C is still better than that in original case. The electricity consumptions of the CRACs can be saved by approximately 146 and 195 kWhr/day with the most optimal configuration.
Abbreviations
CAC Cold aisle containment
COP Coefficient of performance
CPU Central processing unit
CRACs Computer room air-conditioning units
DC Data center
DES Detached Eddy Simulations
HVAC Heating, ventilation, and air conditioning
MTP Measuring temperature point
MVP Measuring velocity point
OHA Open hot aisle
RSM Reynolds Stress Model
SAT Supply air temperature
STP Simulated temperature point
SVP Simulated velocity point
TP Temperature point
UFAD Under-floor air distribution
Nomenclature
W1 Length of each server, m
C1 Distance between the rack rear door and the terminal of the bottom server, m
C2 Distance between the rack front door and front vertical side of the top server, m
D Distance between the front vertical sides of the bottom and the top servers, m
L1 Length of each rack.
Daily cooling energy saving, kWhr
Daily total electricity saving for CRAC units, kWhr
Specific heat capacity of air, kJ/(kg K)
Mass of air, kg
Air density, kg/m3
Volume of air from the CRAC units, m3
Air velocity through the air outlet of the CRAC units, m/s
Area of air vent of each CRAC, m2
SAT difference between the original and optimal model, K
SAT of case 1, °C
SAT of case 9, °C
SAT of the selected case, °C
x Number of the optimum case
COP of CRAC units
Average velocity vector
Static pressure, kPa
Static temperature, kPa
Gravitational acceleration vector
Effective fluid viscosity
Thermal conductivity
Volumetric heat sources
U Unit of server dimension
Acknowledgments
We also want to acknowledge Information Center in Jiangpu Campus of Nanjing Tech University, Nanjing, China, for providing the experimental site.
Disclosure statement
No potential conflict of interest was reported by the author(s).