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    Yogendra joshi ga_tech Yogendra joshi ga_tech Presentation Transcript

    • Characterizing Air Flows and Thermal Responses to Help Sustainable Data Centers Yogendra Joshi G.W. Woodruff School of Mechanical Engineering Georgia Institute of Technology Atlanta, GA 30332, U.S.A. Acknowledgements: Intel, IBM, Department of Energy, National Science Foundation (NSF), Triad Tiles, APCTAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012 1
    • Measuring Air Flows in Data Centers Designed and built by McKenney’sTAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012
    • Details of the CEETHERM data center and the location of the server simulator 42 U 0.09m. 3 1/2" Downflow Upflow Upflow Downflow CRAC 1 CRAC 2 CRAC 3 CRAC 4 13 14 0.44m. Compute rack Compute rack 10 U 1-5 1/2" 12 11 Empty rack Empty rack Compute rack Compute rack Power distribution 10 Test rack Test rack Compute rack Compute rack 9 unit Server Compute rack Compute rack Test rack 7 0.44m. Simulatror 8.75m 8 1-5 1/2" 10 U Test rack Test rack Compute rack Compute rack 5 6 1.98m. Power Empty rack Empty rack Compute rack Compute rack 3 4 distribution Power (6-6") unit distribution unit Compute rack Compute rack 1 2 Note: 0.44m. Perforated tile dampers 10 U Storage Network 1-5 1/2" on tiles 1-4, 7,11-14 are PIV measurement plane closed during the D experiments D O O O O R R Downflow CRAC 6 Downflow CRAC 5 0.44m. 10 U 1-5 1/2" 6.4m 6.4m Experimental section Computational section Only Tiles 5,6,8,9,10 are open during the experiment. All 0.53m. other tiles are closed. 1-9" CRAC 1 and CRAC 6 are simultaneously operatedTAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012
    • Experimental Facilities Fan speed and Heat setting dials 3-D PIV system • 3-D Stereoscopic PIV (Particle Image Velocimetry system for room level air flow mapping. Server Simulator • 22.8 kW Server Simulator with adjustable fan and Perforated floor heater settings to simulate a variety of heat loads. tiles with dampersTAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012 4
    • How much air flow rate is required to cool a 20kW rack? Typical Raised floor air distribution system Server Air requirements Server cold ∆T=20°C Server hot A 20kW Server requires ~ 0.996 m3/s air exit air inlet (2,110 CFM for a ∆T=20°C) Tin=27°C Tout =47°C A 2x2 (4 ft2, 0.3716 m2) opening with no tile V ~ 2.68 m/s (~6 mph) Only tile (no Damper) 56%opening; Area = 0.208 m2 V ~ 4.788 m/s (~10.7 Servers mph) Tile with dampers (26% open); Area = 0.0977 m2 V ~ 10.2 m/s (~22.8 mph)Perforated floor Server pressure drop tileTAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012
    • Rack air flow boundaries for a 22kW rack (0.754 m3/s of tile air flow) 5 Velocity (m/s) 4 0 1.25 2.5 3.75 5 62% of the air requirement; Velocity (m/s) 3 about double at air inlet temp. Aisle Top 2 1 0 of 30 oC 0 100 200 300 400 500 600 700 0 150 300 450 600 -1 Distance measured from the centre of cold aisle (mm) Distance measured from the center of the cold aisle (mm) Top aisle boundary U u-component v-component 1950 2000 1950 2000 1800 2000 1800 1950 1800 1800 Aisle top Height of the server simulator measured from the perforated floor tile (mm) 1800 Height of the server simulator measured from the perforated floor tile (mm) Height of the the server simulator measured from the perforated tile (mm) (mm) 1650 1650 1800 1800 1650 Velocity (m/s) 1600 65% of perf. tile air flow is unutilized Height of server simulator measured from the perforated floor floor tile 1600 1500 Velocity (m/s) 1500 6 1650 Velocity (m/s) 0.8 1500 5.5 1600 5.5 Velocity (m/s) 1400 1350 0.792 1350 5 1500 1350 and escapes from the top. 5.496 5.5 5.038 1400 1200 0.726 4.5 1350 Tile surface 5.496 Ascending column of air is pushed 1400 Rack Height (mm) 0.66 1200 1200 4.58 5.038 1200 1200 Rack Height (mm) 4 Rack Height (mm) 0.594 4.122 4.58 1050 1200 1200 1000 900 0.528 0.462 1050 3.5 3 1050 1050 towards the uniform flow. Highly non rack inlet. 3.664 4.122 3.206 3.664 1000 900 900 1000 800 750 0.396 0.33 2.5 Compression due to entrainment 900 3.206 2.748 2.748 800 Reversed flow at the ends result in 2 750 2.29 750 800 600 600 0.264 0.198 1.5 causes a steady increase in v-comp 750 600 2.29 1.832 1.832 600 velocity sucked into plenum air being 600 1 1.374 600 1.374 600 450 0.132 0.916 0.5 450 400 0.066 450 0.916 0.458 300 0 450 400 0.458 400 200 150 0 300 Peaks and valleys in velocity field 300 300 0 0 150 200 0 0 150 relate to damper geometry 150 200 Aisle Center 0 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 0 0 0 Rack Inlet 0 Velocity (m/s) Aisle center 150 300 450 600 Rack Inlet -2.5 -1.5 -0.5 0.5 1.5 2.5 3.5 4.5 -2.5 -1.5 -0.5 0.5 1.5 2.5 3.5 4.5 U 6 u-component v-component Distance measured from the centre of cold aisle (mm) Velocity (m/s) Rack Velocity (m/s) Velocity (m/s) Velocity (m/s) U U u-component u-component v-component v-component 5 inlet Aisle center 4 0 .5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 Rack inlet 0 .5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 Velocity (m/s) 3 Tile Surface u-component suggests entrainment Tile Surface 2 Deviation from normal to slanting 1 Entrainment predominant at 150 tile surface and subsides at the aisle top 0 the 300 450 600 Air flow at the bottom half of the rackcentre ofaffected by the perf. tile flow -1 0 -2 150 100 300 is cold aisle (mm) 200 450 300 600 Distance measured from the center of the cold Distance measured from the 400 500 600 700 Distance measured from the centre of cold aisle (mm) 25% reduction in flowdue to reversed flow at the tile surface -ve v component is compared to surface aisle (mm) U Tile case where of no air supply from tile u-component v-component Tile surfaceTAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012 6
    • Comparison of cold aisle air distribution for high and low density racks 1950 Height of the server simulator measured from the perforated floor tile (mm) 1950 1800 1800 Height of the server simulator measured from the perforated floor tile (mm) Velocity (m/s) 1650 1650 3 Velocity (m/s) 2.8 1500 6 1500 2.6 5.5 1350 1350 2.4 5 2.2 1200 4.5 1200 2 4 1050 3.5 1050 1.8 1.6 3 900 900 1.4 2.5 750 2 750 1.2 1.5 1 600 1 600 0.8 0.5 0.6 450 450 0 0.4 300 300 0.2 150 150 0 0 150 300 450 600 0 150 300 450 600 Distance measured from the centre of cold aisle (mm) Distance measured from the centre of cold aisle (mm) 650 CFM (6.5 kW rack) 2500 CFM (22 kW rack) Study suggests that there is a limit to the amount of useful air discharged from the perf tile.TAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012 7
    • Grid based Temperature Measurement Consist of 256 thermo couple sensors Type T Copper Constantan Thermocouples Measurement accuracy of ±0.2°C Response time of 4ms/channel Complete temperature mapping of the cold/hot aisle.TAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012 8
    • 6 5 Complete 3-D temperature mapping 4 3 2 1 3 2 1 6 planes along the height 10 planes along the width of the cold aisle 5 planes along the depth of the rackTAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012 9
    • Effect of high perf. tile flow (0.667 m3/s, 1414 CFM)) on cold and hot aisletemperature profiles (TCRAC Supply= 12.3°C) Velocity profile at Aisle top Hot aisle Cold aisle temperature temperature map map • High velocity discharge • Hot pocket in the cause adverse pressure lower half of the gradients at rack inlet rack due to reduced • Pocket of hot air due to air intake and reversed flow in the cold recirculating flows. aisle. Velocity profile at perf. tile surfaceTAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012 10
    • Effect of low perf. tile flow (0.227 m3/s, 586 CFM)) on cold and hot aisletemperature profiles (TCRAC Supply= 12°C) Velocity profile at Aisle top Hot aisle Cold aisle temperature temperature map map • Higher temperature • Absence of reversed flows gradients in the hot aisle • Hot air pocket has vanished • Temperatures increase in • Hot air influx into the aisle at the upper half of the rack the top Velocity profile at perf. tile surfaceTAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012 11
    • Real time server measurements 12TAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012 12
    • Rack Rear view with fan and the power supply details Rack Blade Center BC-6 • Each rack accommodates 6 Blade Center • Each Blade Center has 14 BC-5 Blades • Each Blade has 2 processors (total 168 BC-4 DC processors per rack) Processor 1 and 2 • Processor temperature is BC-3 measured for each processor • Air inlet temperature is BC-2 measured for each blade center 0 2S L BC-1 BladeTAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012
    • Effect of Perforated Tile Flow on CPU Temperature and Fan Speed 100 % CRAC VFD setting (~12,000 CFM) ComparisonRackD6.wmvTAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012
    • Effect of Perforated Tile Flow on CPU Temperature and Fan Speed 60 % CRAC VFD setting (~7,000 CFM) CRAC_60_Celcius.wmvTAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012
    • Multi-University NSF I/UCRC E3S Center: Compact Models of ContainedAisles K=13.2 Velocity Static (m/s) Pressure (Pa) 16TAG/GT Sustainable HPC Infrastructure Workshop, Atlanta GA, Feb. 24, 2012