03 - 630A4-22-700 Appx A-CFD Analysis.pdf
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- Y1BG--Brooklyn EHRM Infrastructure Upgrades Construction VA Medical Center Brooklyn, NY 630A4-22-700
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- 36C77626B0002
About this file
This document is a Computational Fluid Dynamics (CFD) modeling study for the Brooklyn VA Data Hall, conducted by Resolved Analytics. The study examined airflow, temperature, and pressure distribution under four different scenarios involving the operation of three Computer Room Air Conditioning (CRAC) units. Each case simulated a different configuration: Case 1 with all three CRAC units active, and Cases 2-4 with one CRAC unit offline at a time.
The CFD modeling used a three-dimensional, turbulent, single-phase air model with the Realizable K-Epsilon turbulence model and an ideal gas model. The data hall contained 53 total racks (37 active), with a total room load of 125.3 kW. Consistent across all cases, the rack inlet temperatures averaged 75.0°F, and the CRAC return temperatures were consistently 95.0°F. The flow patterns consistently showed high-velocity cold air jets coming through floor tiles, with slight variations in pressure drop between cases ranging from 0.099" to 0.125" water column when operating at a design flow rate of approximately 20,100 CFM.
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Text version
Brooklyn VA Data Hall Computational Fluid Dynamics Modeling Study
Results Rev.1 Highly Confidential
December 12, 2024
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• Spees Design Build contracted Resolved Analytics (RA) to perform CFD modeling in support of their Brooklyn VA Data Hall project.
• The CFD modeling will be used to evaluate the spatial distribution of airflow, temperature and pressure as additional CRAC units have been added to the existing data hall.
• Four CFD simulation cases will be run:
• Case 1: All three CRACs in service at a reduced load
• Case 2: CRAC 1 out of service with remaining two CRACs at 100% load
• Case 3: CRAC 2 out of service with remaining two CRACs at 100% load
• Case 4: CRAC 3 out of service with remaining two CRACs at 100% load
• Additional model simulation cases can be provided as needed. These are to be determined and are not covered under the present scope of work.
• Profiles of velocity, temperature, pressure will be reported along with the hot air return temperatures and rack inlet temperatures.
Background
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• A fully three-dimensional, turbulent, single-phase (air), steady-state CFD model will be used to simulate the flow profile within the data hall.
• A steady-state modeling methodology will be used where the governing equations of fluid motion are iteratively solved to convergence ensuring mass, momentum, and energy conservation.
• The Realizable K-Epsilon turbulence model will be used.
• The air will be simulated using the ideal gas model to allow for density changes due to temperature and pressure.
Simulation Basics
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• The CFD modeling will simulate the transfer of heat from the servers to the air and subsequent cooling by the CRAC Units.
• Underfloor cooling provided by Three (3) CRAC Units
• Cases 2-4: Underfloor cooling provided by Two (2) CRAC Units
• Two aisles of server racks [39 total racks]
• 27 Standard Density Racks
• 6 Main Distribution Racks
• 4 Active
• 2 Passive
• 6 Horizontal Distribution Racks
• Two Uninterruptable Power Supply Units
• Only one is active at a time
General Conditions – Cases 1-4
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Data Hall Layout – Plan View
CRACs (3 Total)
Cold Air Tile Openings (56%
Open Area)
UPS
(Active)
MDA Racks (Active)
MDA Racks (Passive)
MDA Racks (Passive)
SD Racks (Between Arrows)
HDA Racks
SD Racks (Between Arrows)
HDA Racks
SD Racks (Between Arrows)
HDA Racks
UPS
(Inactive)
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CFD Model Geometry and Boundaries Equipment Rack Exhausts – Red
CRAC Return Intakes - Orange
Cold Air Floor Tiles – Purple
CRAC Supplies - Green
Equipment Rack Inlets – Blue
UPS - Yellow
CRAC 1
CRAC 2
CRAC 3
Cold Aisle Containment Curtains – Dark Blue
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• Case 1: All Three CRACs operating at equal load and supplying air @ 75°F with
• CRAC flow rate = 6,700 CFM each [Total = 20,100 CFM]
• Case 2: CRAC 1 offline with two CRACs operating at equal load and supplying air @ 75°F
• CRAC flow rate = 10,050 CFM each [Total = 20,100 CFM]
• Case 3: CRAC 2 offline with two CRACs operating at equal load and supplying air @ 75°F
• CRAC flow rate = 10,050 CFM each [Total = 20,100 CFM]
• Case 4: CRAC 3 offline with two CRACs operating at equal load and supplying air @ 75°F
• CRAC flow rate = 10,050 CFM each [Total = 20,100 CFM]
Model Inputs and Process Conditions – Cases 1-4
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For all cases:
• 53 Racks total:
• 27 Standard (SD) Cabinets @ 160 CFM/kW & 3.5 kW load each
• 4 Main Distribution Area (MDA) Racks @ 160 CFM/kW & 3.5 kW load each
• Additional 2 MDA Racks included, but are assumed passive at 0kW load each
• 6 Horizontal Distribution Area (HDA) Racks @ 160 CFM/kW & 2.8 kW load each
• UPS at 0 kW load
• Total room kW load = 125.3 kW
• Total CFM provided for Room = 20,100 CFM
• Cold Air Floor Tiles are 56% open area
Model Inputs and Process Conditions – Cases 1-4
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Case 1 Results 3 CRACs Active
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3D Velocity Contour, Data Hall, Case 1
Highest velocity flow entering the CRAC units and flowing around cold side containment
Velocities < 8 ft/s filtered out for clarity.
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3D Temperature Contour, Case 1 Room at held at a constant temperature
Average CRAC Return Temp:
95.0°F
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Velocity Profile, 1’ Below Floor, Case 1
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Velocity Profile, 4’ Elevation, Case 1
Higher velocity coming in through the floor tiles
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Velocity Profile, Mid-Plane, Case 1 High velocity plumes from floor tiles dictate the flow patterns in the cold side containment zones.
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Temperature Profile, 4’ Elevation, Case 1 Room is held at a constant temperature of 95°F
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Rack Inlet Temperatures, Case 1
Avg Rack Inlet Temp = 75.0°F Local Max = 75.0°F
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3D Pressure Contour, Case 1 Avg CRAC Supply Pressure = 0.083”wc Avg Rack Inlet Pressure = 0.002” wc dP CRACs to Racks = 0.081” wc Avg Rack Outlet Pressure = 0.002” wc Avg CRAC Return Pressure = -0.016”wc dP Rack Outlets to CRAC Returns = 0.018” wc Cold Side dP + Hot Side dP, Avg = 0.099”wc
Highest gradient is from underfloor zone through floor tiles to data hall.
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• CFD Model Simulation completed for Case 1 case with all 3 CRAC units in service with design IT rack loads
• 37 total Racks, 31 at 3.5kW load, 6 at 2.8kW load [125.3kW total]
• 160 CFM/kW rack flowrate [Required flow = 160*125.3 = 20,048 CFM]
• CRAC flows in Case 1 model case: Design value of 6,700 CFM each at 75°F cold air supply [total =
20,100 CFM]
• Flow patterns predicted exhibit high velocity cold air jets through floor tiles.
• Rack Inlet Temperatures:
• Avg = 75.0°F
• Local Max = 75.0°F
• Avg. CRAC return temperature = 95.0°F
• Avg. CRAC pressure drop from Supply to Return: 0.099” wc [@ flow of 6,700
CFM]
Summary - Case 1
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Case 2 Results 2 CRACs Active, CRAC 1 Inactive
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CFD Model Geometry and Boundaries, Case 2
CRAC 1
(Offline)
CRAC 2
CRAC 3
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3D Velocity Contour, Data Hall, Case 2
Highest velocity flow entering the CRAC units and flowing around cold side containment
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3D Temperature Contour, Case 2 Room at held at a constant temperature
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Velocity Profile, 1’ Below Floor, Case 2
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Velocity Profile, 4’ Elevation, Case 2
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Velocity Profile, Mid-Plane, Case 2 High velocity plumes from floor tiles dictate the flow
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Temperature Profile, 4’ Elevation, Case 2 Room is held at a
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Rack Inlet Temperatures, Case 2
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3D Pressure Contour, Case 2 Avg CRAC Supply Pressure = 0.088”wc Avg Rack Inlet Pressure = -0.01” wc dP CRACs to Racks = 0.098” wc Avg Rack Outlet Pressure = -0.01” wc Avg CRAC Return Pressure = -0.037”wc dP Rack Outlets to CRAC Returns = 0.027” wc Cold Side dP + Hot Side dP, Avg = 0.125”wc
Highest gradient is from
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• CFD Model Simulation completed for Case 2 case with 2 CRAC units (CRAC 1 Offline) in service with design IT rack loads
• 37 total Racks, 31 at 3.5kW load, 6 at 2.8kW load [125.3kW total]
• 160 CFM/kW rack flowrate [Required flow = 160*125.3 = 20,048 CFM]
• CRAC flows in Case 2 model case: Design value of 10,050 CFM each at 75°F cold air supply [total =
20,100 CFM]
• Flow patterns predicted exhibit high velocity cold air jets through floor tiles.
• Rack Inlet Temperatures:
• Avg = 75.0°F
• Local Max = 75.0°F
• Avg. CRAC return temperature = 95.0°F
• Avg. CRAC pressure drop from Supply to Return: 0.125” wc [@ flow of 10,050
Summary - Case 2
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Case 3 Results 2 CRACs Active, CRAC 2 Inactive
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CFD Model Geometry and Boundaries, Case 3
CRAC 1
CRAC 2
(Offline)
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3D Velocity Contour, Data Hall, Case 3
Highest velocity flow entering the CRAC units and flowing around cold side containment
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3D Temperature Contour, Case 3 Room at held at a constant temperature
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Velocity Profile, 1’ Below Floor, Case 3
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Velocity Profile, 4’ Elevation, Case 3
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Velocity Profile, Mid-Plane, Case 3 High velocity plumes from floor tiles dictate the flow
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Temperature Profile, 4’ Elevation, Case 3 Room is held at a
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Rack Inlet Temperatures, Case 3
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3D Pressure Contour, Case 3 Avg CRAC Supply Pressure = 0.09”wc Avg Rack Inlet Pressure = 0.004” wc dP CRACs to Racks = 0.086” wc Avg Rack Outlet Pressure = 0.003” wc Avg CRAC Return Pressure = -0.022”wc dP Rack Outlets to CRAC Returns = 0.025” wc Cold Side dP + Hot Side dP, Avg = 0.111”wc
Highest gradient is from
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• CFD Model Simulation completed for Case 3 case with 2 CRAC units in service (CRAC 2 Offline) with design IT rack loads
• 37 total Racks, 31 at 3.5kW load, 6 at 2.8kW load [125.3kW total]
• 160 CFM/kW rack flowrate [Required flow = 160*125.3 = 20,048 CFM]
• CRAC flows in Case 2 model case: Design value of 10,050 CFM each at 75F cold air supply [total =
20,100 CFM]
• Flow patterns predicted exhibit high velocity cold air jets through floor tiles.
• Rack Inlet Temperatures:
• Avg = 75.0°F
• Local Max = 75.0°F
• Avg. CRAC return temperature = 95.0°F
• Avg. CRAC pressure drop from Supply to Return: 0.111” wc [@ flow of 10,050
Summary - Case 3
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Case 4 Results 2 CRACs Active, CRAC 3 Inactive
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CFD Model Geometry and Boundaries, Case 4
CRAC 1
CRAC 2
(Offline)
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3D Velocity Contour, Data Hall, Case 4
Highest velocity flow entering the CRAC units and flowing around cold side containment
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3D Temperature Contour, Case 4 Room at held at a constant temperature
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Velocity Profile, 1’ Below Floor, Case 4
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Velocity Profile, 4’ Elevation, Case 4
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Velocity Profile, Mid-Plane, Case 4 High velocity plumes from floor tiles dictate the flow
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Temperature Profile, 4’ Elevation, Case 4 Room is held at a
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Rack Inlet Temperatures, Case 4
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3D Pressure Contour, Case 4 Avg CRAC Supply Pressure = 0.1”wc Avg Rack Inlet Pressure = 0.008” wc dP CRACs to Racks = 0.092” wc Avg Rack Outlet Pressure = 0.008” wc Avg CRAC Return Pressure = -0.018”wc dP Rack Outlets to CRAC Returns = 0.026” wc Cold Side dP + Hot Side dP, Avg = 0.118”wc
Highest gradient is from
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• CFD Model Simulation completed for Case 4 case with 2 CRAC units in service (CRAC 3 Offline) with design IT rack loads
• 37 total Racks, 31 at 3.5kW load, 6 at 2.8kW load [125.3kW total]
• 160 CFM/kW rack flowrate [Required flow = 160*125.3 = 20,048 CFM]
• CRAC flows in Case 2 model case: Design value of 10,050 CFM each at 75°F cold air supply [total =
20,100 CFM]
• Flow patterns predicted exhibit high velocity cold air jets through floor tiles.
• Rack Inlet Temperatures:
• Avg = 75.0°F
• Local Max = 75.0°F
• Avg. CRAC return temperature = 95.0°F
• Avg. CRAC pressure drop from Supply to Return: 0.118” wc [@ flow of 10,050
Summary - Case 4
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Summary – All Cases
Case 1 (All CRACs Online)
Case 2 (CRAC 1 Offline) Case 3 (CRAC 2 Offline) Case 4 (CRAC 3 Offline)
Avg Rack Inlet Temp 75°F 75°F 75°F 75°F
Max Rack Inlet Temp 75°F 75°F 75°F 75°F
Avg CRAC Return Temp 95°F 95°F 95°F 95°F
Avg CRAC Pressure Drop 0.099” w.c. 0.125” w.c. 0.111” w.c. 0.118” w.c.
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File details come from the government source that posted it. Updated .