Transient Characterization of Data Center Racks

2016 ◽  
Author(s):  
Yogesh Fulpagare ◽  
Yogendra Joshi ◽  
Atul Bhargav
Keyword(s):  
Data Center ◽  
Heat Dissipation ◽  
Total Heat ◽  
Thermal Mass ◽  
Cfd Model ◽  
Transient Effects ◽  
Air Temperatures ◽  
Fan Speed ◽  
Facility Level ◽  
Storage Demand

The increased computational and storage demand has increased the heat dissipation of servers in data centers. The flow inside the data center is highly dynamic due to various parameters such as server workload, server fan speed, tile porosity, Computer Room Air Conditioning (CRAC) air flowrates, CRAC supply & return air temperatures and data center cold & hot aisle arrangements. Data center facility level transient CFD analysis was reported in recent literature which needs weeks to accomplish the computation. Hence, such facility level simulations are difficult to achieve with good accuracy. The main contributions of this paper are transient experiments, transient CFD model & transient effects on thermal and flow field due to variation in server load of server rack inside the raised floor plenum data center. In the current study we have developed a transient CFD model of three racks in a raised floor plenum data center room with cold and hot aisle containment based on experiments. The middle 42U (1U = 4.45 cm) rack houses four server simulators each having height of 10U. The flow tiles supply the cold air as inlet with average velocity of 1.53 m/s at 17°C. All the rack servers were modelled with 75% porosity and estimated thermal mass Each server simulator was assigned a total heat dissipation of 2500 W, with a total heat load of 10 kW per rack. The effect on rack inlet and outlet air temperatures were monitored by providing server heat loads as step & ramp inputs to the middle simulator rack. The results show that the rack level transient effects are significant and cannot be ignored.

Raised Floor Computer Data Center: Effect on Rack Inlet Temperatures When Adjacent Racks Are Removed

2003 ◽  
Author(s):  
Roger Schmidt ◽  
Ethan Cruz
Keyword(s):  
Data Center ◽  
Control Volume ◽  
Fluid Dynamic ◽  
Computer Code ◽  
Cfd Model ◽  
Computer Data ◽  
Center Effect ◽  
Air Temperatures ◽  
Baseline Case ◽  
Finite Control

This paper focuses on the effect on inlet rack air temperatures when adjacent racks are removed. Only the above floor (raised floor) flow and temperature distributions were analyzed for various air flowrates exhausting from the perforated tiles and the rack. A Computational Fluid Dynamic (CFD) model was generated for the room with electronic equipment installed on a raised floor with particular focus on the effects on rack inlet temperatures of these high powered racks. The baseline case was with forty racks of data processing (DP) equipment arranged in rows in a data center cooled by chilled air exhausting from perforated floor tiles. The chilled air was provided by four A/C units placed inside a room 12.1 m wide × 13.4 m long. Since the arrangement of the racks in the data center was symmetric only one-half of the data center was modeled. To see the effect of missing racks adjacent to high powered racks various configurations were analyzed. The numerical modeling was performed using a commercially available finite control volume computer code called Flotherm (Trademark of Flomerics, Inc.). The flow was modeled using the k-e turbulence model. Results are displayed to provide some guidance on the design and layout of a data center.

A Numerical Steady State and Dynamic Study in a Data Center Using Calibrated Fan Curves for CRACs and Servers

2013 ◽  
Author(s):  
Sami A. Alkharabsheh ◽  
Bahgat Sammakia ◽  
Saurabh Shrivastava ◽  
Michael Ellsworth ◽  
Milnes David ◽  
...  
Keyword(s):  
Dynamic Model ◽  
Data Center ◽  
Power Dissipation ◽  
Time History ◽  
Boussinesq Approximation ◽  
Design Guidelines ◽  
Thermal Mass ◽  
Transient Model ◽  
History Of ◽  
Fan Speed

This study presents the results of a detailed parametric study for a data center that is air cooled using a set of four CRAC units in a cold/hot aisle raised floor configuration. The fans of the CRAC units and the servers are calibrated using their practical characteristics fan curves. A commercial CFD code is utilized for this purpose in which the buoyancy forces are taken into account. The k-epsilon model and the Boussinesq approximation are used to model the turbulent airflow and the buoyancy effect, respectively. A dynamic model is developed to take into account the changes in flow rates and power dissipation in the data center environment. The current dynamic model does not take into account the thermal mass of the CRAC units or the servers. The effect of the CRAC fan speed, instantaneous change in power dissipation, tiles perforation ratio, and servers fan speeds on the total flow rate in the room and the inlet temperatures of the racks are investigated. In the transient model, we investigate the effect of different CRAC failure scenarios on the time history of the temperatures and the flow pattern in the data center. Time constants and safe time are estimated from this study. A fundamental understanding of the effect of different data center entities on the flow and the temperatures is developed. Interesting flow patterns are observed in the case of different CRAC failures that could be used to recommend general design guidelines.

Cluster of High-Powered Racks Within a Raised-Floor Computer Data Center: Effect of Perforated Tile Flow Distribution on Rack Inlet Air Temperatures

2004 ◽  
Vol 126 (4) ◽  
pp. 510-518 ◽  
Author(s):  
Roger Schmidt ◽  
Ethan Cruz
Keyword(s):  
Data Center ◽  
Control Volume ◽  
Flow Distribution ◽  
Computer Code ◽  
Cfd Model ◽  
Computer Data ◽  
Air Temperatures ◽  
Finite Control ◽  
Computational Fluid Dynamics Cfd ◽  
Tile Flow

This paper focuses on the effect on rack inlet air temperatures as a result of maldistribution of airflows exiting the perforated tiles located adjacent to the fronts of the racks. The flow distribution exiting the perforated tiles was generated from a computational fluid dynamics (CFD) tool called Tileflow (trademark of Innovative Research, Inc.). Both raised floor heights and perforated tile-free areas were varied in order to explore the effect on rack inlet temperatures. The flow distribution exiting the perforated tiles was used as boundary conditions to the above-floor CFD model. A CFD model was generated for the room with electronic equipment installed on a raised floor. Forty racks of data processing (DP) equipment were arranged in rows in a data center cooled by chilled air exhausting from perforated floor tiles. The chilled air was provided by four A/C units placed inside a room 12.1 m wide×13.4 m long. Because the arrangement of the racks in the data center was symmetric, only half of the data center was modeled. The numerical modeling for the area above the raised floor was performed using a commercially available finite control volume computer code called Flotherm (trademark of Flomerics, Inc.). The flow was modeled using the k-e turbulence model. Results are displayed to provide some guidance on the design and layout of a data center.

Facility Cooling Failure Analysis of Direct Liquid Cooling System in Data Centers

2018 ◽  
Author(s):  
Sami Alkharabsheh ◽  
Udaya L. N. Puvvadi ◽  
Bharath Ramakrishnan ◽  
Kanad Ghose ◽  
Bahgat Sammakia
Keyword(s):  
Data Center ◽  
Cooling System ◽  
Rate Of Change ◽  
Operating Conditions ◽  
Thermal Mass ◽  
Liquid Cooling ◽  
Chip Temperature ◽  
Fan Speed ◽  
Liquid Cooling System ◽  
The Impact

This work experimentally studies the impact of facility cooling failure of a direct liquid cooling (DLC) system on the IT equipment (ITE). The facility side of a DLC system removes the heat from a secondary loop — in direct contact with the ITE — and discard it in a chiller loop or ambient. The CPU utilization and coolant set point temperature (SPT) are varied to understand the effect of failure under different operating conditions. The ITE response is studied in terms of chip temperature and power, and fan speed. It was found that failure of the facility cooling system is not hazardous to the IT operation. The rate of change in temperature after failure is low and is sufficient to turn the ITE off safely. This is attributed to the surrounding air in the data center and the thermal mass of the cooling system.

Characterization of a Server Thermal Mass Using Experimental Measurements

2011 ◽  
Author(s):  
Mahmoud Ibrahim ◽  
Furat Afram ◽  
Bahgat Sammakia ◽  
Kanad Ghose ◽  
Bruce Murray ◽  
...  
Keyword(s):  
Material Properties ◽  
Data Center ◽  
Open Space ◽  
Heat Dissipation ◽  
Thermal Mass ◽  
Experimental Measurements ◽  
Close Monitoring ◽  
Safe Operation ◽  
Dynamic Cooling

The inevitable increase in the heat dissipation of data center facilities is requiring more efficient approaches in the operation of a data center. Dynamic cooling has been proposed as the approach for enhancing the energy efficiency. Dynamic cooling involves close monitoring of the data center environment with time, using sensors, and taking real time decisions on allocating the cooling resources based on the location of hotspots and concentration of workloads. In order to address this approach, knowing the time it takes for a facility to reach steady state after any variation is crucial for ensuring safe operation of the electronic equipment at all times, and it is a function of thermal mass. The thermal mass of an object is the amount of mass capable of withholding heat, and the time it takes to dissipate that heat into the environment is a function of the material properties. In this study, we use a typical 2U server and explain a procedure in obtaining its thermal mass. The server is operated at different controlled power levels while measurements of fans speed, component temperatures, and inlet and outlet temperatures are taken with time. For the first set of experiments, the server is kept inside a chamber and for the second set it is kept in open space. Ultimately the experimental measurements obtained will be used to obtain a compact model to approximate thermal mass of different servers.

Cluster of High Powered Racks Within a Raised Floor Computer Data Center: Effect of Perforated Tile Flow Distribution on Rack Inlet Air Temperatures

2003 ◽  
Author(s):  
Roger Schmidt ◽  
Ethan Cruz
Keyword(s):  
Data Center ◽  
Control Volume ◽  
Flow Distribution ◽  
Computer Code ◽  
Cfd Model ◽  
Computer Data ◽  
Air Temperatures ◽  
Finite Control ◽  
Computational Fluid Dynamics Cfd ◽  
Tile Flow

This paper focuses on the effect on inlet rack air temperatures as a result of maldistribution of airflows exiting the perforated tiles located adjacent to the fronts of the racks. The flow distribution exiting the perforated tiles was generated from a computational fluid dynamics (CFD) tool called Tileflow (Trademark of Innovative Research, Inc.). Both raised floor heights and perforated tile free area were varied in order to explore the effect on rack inlet temperatures. The flow distribution exiting the perforated tiles was used as boundary conditions to the above floor CFD model. A CFD model was generated for the room with electronic equipment installed on a raised floor. Fourty racks of data processing (DP) equipment were arranged in rows in a data center cooled by chilled air exhausting from perforated floor tiles. The chilled air was provided by four A/C units placed inside a room 12.1 m wide × 13.4 m long. Since the arrangement of the racks in the data center was symmetric only one-half of the data center was modeled. The numerical modeling for above the raised floor was performed using a commercially available finite control volume computer code called Flotherm (Trademark of Flomerics, Inc.). The flow was modeled using the k-e turbulence model. Results are displayed to provide some guidance on the design and layout of a data center.

Raised Floor Computer Data Center: Effect of Rack Inlet Temperatures When Rack Flowrates Are Reduced

2003 ◽  
Author(s):  
Roger Schmidt ◽  
Ethan Cruz
Keyword(s):  
Data Center ◽  
Control Volume ◽  
Fluid Dynamic ◽  
Computer Code ◽  
Cfd Model ◽  
Computer Data ◽  
Center Effect ◽  
Air Temperatures ◽  
Finite Control ◽  
Heat Loads

This paper focuses on the effect on inlet rack air temperatures when rack flowrates are reduced. Reduced flowrates for the same heat loads results in higher air temperature differences across the rack and thereby higher air temperatures exiting the rack. The effect of the higher rack exhaust temperatures on the inlet rack air temperatures is the focus of this investigation. Only the above floor (raised floor) flow and temperature distributions were analyzed for a range of rack flowrates and with various flowrates exhausting from the perforated tiles. A Computational Fluid Dynamic (CFD) model was generated for the room with electronic equipment installed on a raised floor with particular focus on the effects on rack inlet temperatures of these high powered racks. Fourty racks of data processing (DP) equipment were arranged in rows in a data center cooled by chilled air exhausting from perforated floor tiles. The chilled air was provided by four A/C units placed inside a room 12.1 m wide × 13.4 m long. Since the arrangement of the racks in the data center was symmetric only one-half of the data center was modeled. The numerical modeling was performed using a commercially available finite control volume computer code called Flotherm (Trademark of Flomerics, Inc.). The flow was modeled using the k-e turbulence model. Results are displayed to provide some guidance on the design and layout of a data center.

Raised Floor Computer Data Center: Effect on Rack Inlet Temperatures When High Powered Racks are Situated Amongst Lower Powered Racks

2002 ◽  
Author(s):  
Roger Schmidt ◽  
Ethan Cruz
Keyword(s):  
Data Center ◽  
Control Volume ◽  
Fluid Dynamic ◽  
Computer Code ◽  
Cfd Model ◽  
Computer Data ◽  
Center Effect ◽  
Temperature Distributions ◽  
Air Temperatures ◽  
Finite Control

This paper focuses on the effect on inlet rack air temperatures when high-powered racks are situated amongst lower powered racks in a raised floor data center. Only the above floor (raised floor) flow and temperature distributions were analyzed for various flowrates exhausting from the perforated tiles and with one or two high powered racks placed at various locations amongst the lower powered racks. A Computational Fluid Dynamic (CFD) model was generated for the room with electronic equipment installed on a raised floor with particular focus on the effects on rack inlet temperatures of these high powered racks. Forty racks of data processing (DP) equipment were arranged in rows in a data center cooled by chilled air exhausting from perforated floor tiles. The chilled air was provided by four A/C units placed inside a room 12.1 m wide × 13.4 m long. Since the arrangement of the racks in the data center was symmetric only one-half of the data center was modeled. The numerical modeling was performed using a commercially available finite control volume computer code called Flotherm (Trademark of Flomerics, Inc.). The flow was modeled using the k-e turbulence model. Results are displayed to provide some guidance on the design and layout of a data center.

Modeling Thermal Mass of a Data Center Validated With Actual Data due to Chiller Failure

2011 ◽  
Author(s):  
Vikneshan Sundaralingam ◽  
Steven Isaacs ◽  
Pramod Kumar ◽  
Yogendra Joshi
Keyword(s):  
Data Center ◽  
System Analysis ◽  
Thermal Response ◽  
Actual Data ◽  
Thermal Mass ◽  
Alternative Analysis ◽  
Critical Temperatures ◽  
Air Temperatures ◽  
Power Draw ◽  
Center Section

The task of minimizing the downtime of a data center is becoming increasingly important due to the necessity of availability and maintaining the integrity of the data being handled by the data center. Consequently, a model used to predict the thermal response of a data center would be useful information in designing mechanisms to minimize the downtime during a failure or to serve as an alternative analysis method other than CFD. This paper will focus on a thermodynamic approach of predicting the thermal response of the data center space with the use of lumped system analysis. The model will be developed and validated using actual data from a chiller failure event in the CEETHERM Data Center Laboratory. Events in sequence are: (i) Chiller failure, (ii) Data center shutdown due to critical temperatures and (iii) Chiller restored. To illustrate, the data center section of interest consists of 10 racks of servers (maximum capacity of 24kW for each rack) with a total of 3360 nodes and is chilled using chilled water from the building chiller, through which the cooling resources are distributed using a rear door heat exchanger and a cooling room air conditioning unit (CRAC). The relevant and important data that was recorded in this failure are the: (1) Server inlet temperatures, (2) CPU temperatures, (3) CRAC supply and return air temperatures, (4) Chiller supply and return water temperature, (5) Chiller flow rate, (6) Data center space temperature and humidity, (7) Server power draw and (8) CRAC fan speeds.

Controller to Regulate Maximum Server CPU Temperatures in a Rack by Varying CRAC Supply Air Temperatures

2012 ◽  
Author(s):  
Vikneshan Sundaralingam ◽  
Yogendra Joshi ◽  
Vaibhav Arghode
Keyword(s):  
Time Domain ◽  
Data Center ◽  
Air Conditioning ◽  
Data Centers ◽  
Infrastructure Management ◽  
Air Temperatures ◽  
Integral Action ◽  
Level Information ◽  
Facility Level ◽  
Space Conditions

Conventionally, raised floor data centers operate using controllers that only maintain constant data center space conditions (i.e. supply air temperatures or return air temperatures) at the Computer Room Air Conditioning (CRAC) Unit level with the intention of providing enough cooling for the servers. The objective of this paper is to explore the framework required to design a controller that regulates server CPU temperatures by specifying the supply air temperature of the CRAC. The controller will be an addition to the existing controller used by the CRAC to regulate supply air temperatures. In the discrete-time domain, implementation and the performance of the modified integral action controller is analyzed and other important parameters are compared. As a preliminary attempt, the controller will be designed for a standard 44U cabinet with 42 “1U” servers, where the machines will execute a prescribed compute load variation: (1) step increase in all compute loads and (2) scaled down representation for a rack of servers using utilization trends from one of Google’s data centers. Ultimately, the development of this controller is motivated by the growing interest in Data Center Infrastructure Management (DCIM) where the IT level and facility level information are both used to intelligently plan and manage resources of a data center.

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