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.

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.

Parameter Estimation for Lumped Capacitance Modeling of CRAH Units During Chilled Water Interruption

2015 ◽  
Author(s):  
Hamza Salih Erden ◽  
H. Ezzat Khalifa
Keyword(s):  
Data Center ◽  
Thermal Response ◽  
Experimental Methodology ◽  
Model Parameters ◽  
Thermal Mass ◽  
Sufficient Information ◽  
Thermal Capacitance ◽  
Chilled Water ◽  
Transient Thermal ◽  
Transient Thermal Response

Lumped capacitance models have been introduced to study transient thermal response of data centers. Chilled water interruption of a Computer Room Air Handling (CRAH) unit is one of several failure scenarios of data center cooling infrastructures. In such a scenario, predicting the transient thermal response of the CRAH unit depends requires the determination of the CRAH lumped capacitance model parameters: the thermal capacitance (thermal mass) and the time constant. In this paper, we propose an experimental methodology to extract sufficient information for the lumped capacitance modeling of CRAH units. The method requires measurements of inlet and exit air temperature, air flow rate and CRAH fan power. If the chilled water supply to a CRAH unit is intentionally interrupted in a data center with multiple redundant CRAH units, sufficient information to estimate the CRAH lumped capacitance parameters can be obtained without disturbing the data center operation.

Optimization of Data Center Room Layout to Minimize Rack Inlet Air Temperature

2005 ◽  
Author(s):  
Siddharth Bhopte ◽  
Dereje Agonafer ◽  
Roger Schmidt ◽  
Bahgat Sammakia
Keyword(s):  
Design Optimization ◽  
Air Temperature ◽  
Data Center ◽  
Floor Tile ◽  
Optimization Approach ◽  
Wrong Decision ◽  
Air Temperatures ◽  
Variable Approach ◽  
Entire Height ◽  
Facility Manager

In a typical raised floor data center with alternating hot and cold aisles, air enters the front of each rack over the entire height of the rack. Since the heat loads of data processing equipment continues to increase at a rapid rate, it is a challenge to maintain the temperature within the requirements as stated for all the racks within the data center. A facility manager has discretion in deciding the data center room layout, but a wrong decision will eventually lead to equipment failure. There are many complex decisions to be made early in the design as the data center evolves. Challenges occur such as optimizing the raised floor plenum, floor tile placement, minimizing the data center local hot spots etc. These adjustments in configuration affects rack inlet air temperatures which is one of the important key to effective thermal management. In this paper, a raised floor data center with 4.5 kW racks is considered. There are four rows of racks with alternating hot and cold aisle arrangement. Each row has six racks installed. Two CRAC units supply chilled air to the data center through the pressurized plenum. Effect of plenum depth, floor tile placement and ceiling height on the rack inlet air temperature is discussed. Plots will be presented over the defined range. Now a multi-variable approach to optimize data center room layout to minimize the rack inlet air temperature is proposed. Significant improvement over the initial model is shown by using multi-variable design optimization approach. The results of multi-variable design optimization are used to present guidelines for optimal data center performance.

Mitochondrial membrane transitions in heart and other organs of a hibernator

1988 ◽  
Vol 254 (3) ◽  
pp. E378-E383
Author(s):  
J. K. Raison ◽  
M. L. Augee ◽  
R. C. Aloia
Keyword(s):  
Body Temperature ◽  
Membrane Lipids ◽  
Accurate Determination ◽  
Thermal Response ◽  
Heart Tissue ◽  
Early Summer ◽  
Brown Fat ◽  
Critical Temperatures ◽  
Spermophilus Lateralis ◽  
And Function

Critical temperatures (T) for transitions in both lipid structure and enzyme function of mitochondrial membranes from liver, kidney, brown fat, and heart tissues were determined for the hibernator Spermophilus lateralis at two weekly intervals from early summer to late autumn and during hibernation. For all tissues T fell into one of three groups: those below 4 degrees C (the minimal level of accurate determination), those centered about a mean of 11.9 +/- 1.4 degrees C, and those centered about a mean of 20.9 +/- 1.8 degrees C. The T for tissues from torpid animals and from heart, at all sampling periods, was below 4 degrees C. For liver, kidney, and brown fat the mean T was approximately 21 degrees C in early summer but was lowered later in the season in a two-step process, falling to below 4 degrees C before the animals were exposed to cold and entering torpor. It is concluded that for mitochondria the thermal response of the membrane lipids is altered such that the transition in structure and function is always below the minimum body temperature likely to be experienced by this animal. Heart tissue is exceptional in that the transition is at a temperature consistent with a body temperature of torpor even in summer-active animals.

Energy Conservation Measures of a Primary Data Center on an Academic Campus

2013 ◽  
Author(s):  
Kyosung Choo ◽  
Renan Manozzo Galante ◽  
Michael Ohadi
Keyword(s):  
Energy Conservation ◽  
Data Center ◽  
Power Saving ◽  
Primary Data ◽  
University Of Maryland ◽  
Conservation Measures ◽  
Air Temperatures ◽  
Cold Aisle Containment ◽  
The University ◽  
Energy Conservation Measures

Energy Conservation Measures (ECMs) of the primary data center at the University of Maryland are developed. Measurement and simulation are performed to validate the developed ECMs. Three ECMs — 1) Increase in the return temperature at Computer Room Air Conditionings (CRACs) 2) Cold aisle containment 3) Elimination of unnecessary CRACs — are suggested to reduce energy consumption by optimizing the thermo-fluid flow in the data center. Power savings of 12.7 kW – 17.4 kW and 14.1 kW are obtained by increasing the return air temperatures at the CRACs and performing the cold aisle containment, respectively. In addition, a power saving of 11.2 kW is obtained by turning off CRACs 3 and 8 which have an adverse effect on the data center cooling.

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.

Raised Floor Hybrid Cooled Data Center: Effect on Rack Inlet Air Temperatures When In Row Cooling Units are Installed Between the Racks

2015 ◽  
Author(s):  
Tianyi Gao ◽  
James Geer ◽  
Russell Tipton ◽  
Bruce Murray ◽  
Bahgat G. Sammakia ◽  
...  
Keyword(s):  
Flow Rate ◽  
Data Center ◽  
Heat Load ◽  
Data Centers ◽  
Cooling System ◽  
Air Flow ◽  
Inlet Temperature ◽  
Air Flow Rate ◽  
Air Temperatures ◽  
Cooling Unit

The heat dissipated by high performance IT equipment such as servers and switches in data centers is increasing rapidly, which makes the thermal management even more challenging. IT equipment is typically designed to operate at a rack inlet air temperature ranging between 10 °C and 35 °C. The newest published environmental standards for operating IT equipment proposed by ASHARE specify a long term recommended dry bulb IT air inlet temperature range as 18°C to 27°C. In terms of the short term specification, the largest allowable inlet temperature range to operate at is between 5°C and 45°C. Failure in maintaining these specifications will lead to significantly detrimental impacts to the performance and reliability of these electronic devices. Thus, understanding the cooling system is of paramount importance for the design and operation of data centers. In this paper, a hybrid cooling system is numerically modeled and investigated. The numerical modeling is conducted using a commercial computational fluid dynamics (CFD) code. The hybrid cooling strategy is specified by mounting the in row cooling units between the server racks to assist the raised floor air cooling. The effect of several input variables, including rack heat load and heat density, rack air flow rate, in row cooling unit operating cooling fluid flow rate and temperature, in row coil effectiveness, centralized cooling unit supply air flow rate, non-uniformity in rack heat load, and raised floor height are studied parametrically. Their detailed effects on the rack inlet air temperatures and the in row cooler performance are presented. The modeling results and corresponding analyses are used to develop general installation and operation guidance for the in row cooler strategy of a data center.

Effect of Thermal Characteristics of Electronic Enclosures on Dynamic Data Center Performance

2010 ◽  
Author(s):  
Mahmoud Ibrahim ◽  
Siddharth Bhopte ◽  
Bahgat Sammakia ◽  
Bruce Murray ◽  
Madhusudan Iyengar ◽  
...  
Keyword(s):  
Data Center ◽  
Data Centers ◽  
Characteristic Curve ◽  
Thermal Characteristic ◽  
Thermal Characteristics ◽  
Thermal Mass ◽  
Model Case ◽  
Temperature Boundary ◽  
Data Center Cooling ◽  
Dimensional Parameters

Data centers are the facilities that house large number of computer servers that dissipate high power. Considering the dynamics of the data centers, their efficient thermal management is a big challenge that needs to be addressed. Computational analysis using a CFD code is very useful technique that helps the engineer to understand and solve the data center cooling problem. Several ongoing numerical modeling research efforts assume the computer room air conditioning (CRAC) units as fixed flow devices with constant temperature boundary condition. In reality, CRAC supply temperature is governed by the thermal characteristic curve, as specified by vendor. In this paper, study is presented by incorporating the CRAC thermal characteristic curve in the numerical model. Case studies are presented to show how the segregated high and low powered clusters in a data center may affect the supply temperatures from the CRAC in their vicinity. Another concern that is crucial in analyzing data centers performance precisely is the effect of buoyancy and thermal mass on the facility environment. In some cases, the effect of thermal mass and buoyancy may cause unexpected behaviors such as temperature overshoot or rapid variations in temperature. Non-dimensional parameters are used to demonstrate the effects of thermal mass and buoyancy.

Experimental Measurement of Server Thermal Effectiveness for Compact Transient Data Center Models

2013 ◽  
Author(s):  
James W. VanGilder ◽  
Zachary M. Pardey ◽  
Xuanhang (Simon) Zhang ◽  
Christopher Healey
Keyword(s):  
Heat Exchange ◽  
Data Center ◽  
Physical Property ◽  
Heat Sinks ◽  
Compact Model ◽  
Transient Temperature ◽  
Thermal Mass ◽  
Practical Applications ◽  
Effective Specific Heat ◽  
Transient Data

Server thermal mass can significantly affect the rate at which a data center heats up following a loss of cooling and moderate transient temperature fluctuations due to changing CPU utilization. Recently, a compact server model has been introduced which captures the effects of thermal mass while avoiding the impractical level of detail that would be required by an explicit representation of all relevant server components. Inputs to that model include server mass, overall effective specific heat, and a parameter called the “server thermal effectiveness”. The latter characterizes the server’s ability to transfer heat to/from the airstream passing through it and can take values between zero (no heat exchange) and one (maximum possible heat exchange). Server thermal mass is a physical property of a server and is not influenced by external factors. In order to use the compact model for practical applications, we must experimentally measure the thermal effectiveness of actual servers. The present study reviews the compact model and describes the development of an experimental technique for measuring thermal effectiveness. The technique is validated using simple plate fin heat sinks in place of an actual server. This “server proxy” is sufficiently simple so that it can be modeled accurately in detail in CFD, providing well-controlled benchmark data. CFD and experimental measurements both yield a value of server thermal effectiveness of approximately 0.6, providing confidence in the model and measurement technique for the future characterization of actual servers.

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