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.

Compact Modeling of Forced Flow in Longitudinal Fin Heat Sinks With Tip Bypass

2003 ◽  
Vol 125 (3) ◽  
pp. 319-324 ◽  
Author(s):  
C. B. Coetzer ◽  
J. A. Visser
Keyword(s):  
Pressure Drop ◽  
Heat Sink ◽  
Heat Sinks ◽  
Compact Model ◽  
Forced Flow ◽  
Compact Modeling ◽  
Transfer Coefficients ◽  
Wide Range ◽  
Laminar And Turbulent Flow ◽  
Improved Accuracy

This paper introduces a compact model to predict the interfin velocity and the resulting pressure drop across a longitudinal fin heat sink with tip bypass. The compact model is based on results obtained from a comprehensive study into the behavior of both laminar and turbulent flow in longitudinal fin heat sinks with tip bypass using CFD analysis. The new compact flow prediction model is critically compared to existing compact models as well as to the results obtained from the CFD simulations. The results indicate that the new compact model shows at least a 4.5% improvement in accuracy predicting the pressure drop over a wide range of heat sink geometries and Reynolds numbers simulated. The improved accuracy in velocity distribution between the fins also increases the accuracy of the calculated heat transfer coefficients applied to the heat sinks.

Buildings with environmental quality management, part 2: Integration of hydronic heating/cooling with thermal mass

2017 ◽  
Vol 41 (5) ◽  
pp. 397-417 ◽  
Author(s):  
A Romanska-Zapala ◽  
M Bomberg ◽  
M Fedorczak-Cisak ◽  
M Furtak ◽  
D Yarbrough ◽  
...  
Keyword(s):  
Control Systems ◽  
Design Process ◽  
Architectural Design ◽  
Integrated Design ◽  
Field Performance ◽  
Functional Materials ◽  
Heating System ◽  
Transient Temperature ◽  
Thermal Mass ◽  
Integrated Design Process

The quest for a sustainable built environment brought dramatic changes to architectural design because of the integrated design process. The integrated design process is the modern way to realize “performance architecture,” that is, design with a view to field performance. Integrated design process permits merging of concepts from passive-house designs, solar engineering, and an integration of the building enclosure with mechanical services. In part 1 of this series, the emergence of many new multi-functional materials was discussed. Yet, current innovation is guided by lessons from history. Thermal mass in heavy masonry buildings allowed periodic heating. The authors postulate integration of a hydronic heating system with the walls and the use of smart temperature control of the heating system to modify and optimize the thermal mass contribution. To use the mass of a building, one must accept transient temperature conditions where the indoor temperature varies but is confined by comfort requirements for both summer and winter conditions. On the other side, resiliency requirements dictate that in the absence of electricity the air temperature does not fall below about 12°C over a period of several hours. This requirement implies that summer cooling will likely be separated from the heating systems and that operation of a low-energy building is heavily dependent on the design of smart control systems. Analysis of control systems provided in this article for earth-to-air heat exchangers and cooling of houses with lightweight walls lead us to the requirements of separation between heating and ventilation and needs for different sources of fresh air. Finally, a new concept emerges.

scholarly journals Simulating Convective-Radiative Heat Sinks Effect by means of FEA-based Gaussian Heat Sources and Its Approximate Analytical Solutions for Semi-Infinite Body

2021 ◽  
Author(s):  
Ninh The Nguyen ◽  
John H Chujutalli
Keyword(s):  
Temperature Field ◽  
Heat Source ◽  
Analytical Solutions ◽  
Radiative Heat ◽  
Source Model ◽  
Heat Sinks ◽  
Transient Temperature ◽  
Measured Temperature ◽  
Heat Source Model ◽  
Transient Temperature Field

Abstract FEA-based Gaussian density heat source models were developed to study the effect of convective and radiative heat sinks on the transient temperature field predicted by the available approximate analytical solution of the purely conduction-based Goldak’s heat source. A new complex 3D Gaussian heat source model, incorporating all three modes of heat transfer, i.e., conduction, convection and radiation, has been developed as an extension of the Goldak heat source. Its approximate transient analytical solutions for this 3-D moving heat source were derived and numerically benchmarked with the available measured temperature & weld pool geometry data by Matlab programming with ~5 to 6 times faster than FEA-based simulation. The new complex 3D Gaussian heat source model and its approximate solution could significantly reduce the computing time in generating the transient temperature field and become an efficient alternative to extensive FEA-based simulations of heating sequences, where virtual optimisation of a melting heat source (i.e. used in welding, heating, cutting or other advanced manufacturing processes) is desirable for characterisation of material behaviour in microstructure evolution, melted pool, microhardness, residual stress and distortions.

On the thermal buffering of naturally ventilated buildings through internal thermal mass

2007 ◽  
Vol 580 ◽  
pp. 3-29 ◽  
Author(s):  
J. M. HOLFORD ◽  
A. W. WOODS
Keyword(s):  
Heat Exchange ◽  
Air Temperature ◽  
Natural Ventilation ◽  
Ventilation Rate ◽  
Temperature Cycle ◽  
Thermal Mass ◽  
Thermal Equilibration ◽  
Environment Temperature ◽  
Naturally Ventilated Buildings ◽  
Diurnal Fluctuations

In this paper we examine the role of thermal mass in buffering the interior temperature of a naturally ventilated building from the diurnal fluctuations in the environment. First, we show that the effective thermal mass which is in good thermal contact with the air is limited by the diffusion distance into the thermal mass over one diurnal temperature cycle. We also show that this effective thermal mass may be modelled as an isothermal mass. Temperature fluctuations in the effective thermal mass are attenuated and phase-shifted from those of the interior air, and therefore heat is exchanged with the interior air. The evolution of the interior air temperature is then controlled by the relative magnitudes of (i) the time for the heat exchange between the effective thermal mass and the air; (ii) the time for the natural ventilation to replace the air in the space with air from the environment; and (iii) the period of the diurnal oscillations of the environment. Through analysis and numerical solution of the governing equations, we characterize a number of different limiting cases. If the ventilation rate is very small, then the thermal mass buffers the interior air temperature from fluctuations in the environment, creating a near-isothermal interior. If the ventilation rate increases, so that there are many air changes over the course of a day, but if there is little heat exchange between the thermal mass and interior air, then the interior air temperature locks on to the environment temperature. If there is rapid thermal equilibration of the thermal mass and interior air, and a high ventilation rate, then both the thermal mass and the interior air temperatures lock on to the environment temperature. However, in many buildings, the more usual case is that in which the time for thermal equilibration is comparable to the period of diurnal fluctuations, and in which ventilation rates are moderate. In this case, the fluctuations of the temperature of the thermal mass lag those of the interior air, which in turn lag those of the environment. We consider the implications of these results for the use of thermal mass in naturally ventilated buildings.

Impact of seam types on thermal properties of athletic bodywear

2016 ◽  
Vol 87 (9) ◽  
pp. 1052-1059 ◽  
Author(s):  
Eric Beaudette ◽  
Huiju Park
Keyword(s):  
Thermal Properties ◽  
Laboratory Experiments ◽  
Physical Property ◽  
Property Testing ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Thermal Manikin ◽  
Controlled Environment ◽  
Practical Applications ◽  
Significant Difference

This study investigated the differences in thermal properties of primary seam types used in athletic apparel construction. Traditional seam types, such as overlock and flatlock, as well as adhesive films, were studied. Laboratory experiments in a controlled environment showed that adhesives created a considerably thinner seam than the other methods, while flatlock seaming showed the greatest increase in the garment weight because of dense stitching. A series of thermal manikin tests and statistical analysis showed a significantly higher thermal insulation rating in a bodysuit constructed with flatlock seams, which was found to have lower air permeability than the overlock and adhesive physical property testing samples. There was no significant difference in water vapor transport properties among the three test seams. The findings of this study provide the impacts of seams on thermal properties of active bodywear, which may have practical applications in the sports apparel industry’s decision-making in activewear design and production.

Thermal Management of Downhole Oil and Gas Logging Sensors for HTHP Applications Using Nanoporous Materials

2007 ◽  
Author(s):  
Saeed Rafie
Keyword(s):  
Oil And Gas ◽  
Electrical Response ◽  
Heat Sinks ◽  
Transient Temperature ◽  
Nanoporous Material ◽  
Electronic Components ◽  
Thermal Shield ◽  
One Dimensional ◽  
And Performance ◽  
Downhole Temperature

One of the main challenges in designing oil & gas downhole wireline logging tools for high temperature and high pressure (HTHP) environments is to put together the most efficient thermal packaging to enhance the tool’s temperature survival time. In general, not all electronic components and sensors can withstand severe downhole temperature (max 500 degrees Fahrenheit). For those heat sensitive components, their electrical response and performance either decay or in some cases they completely fail when their temperature exceeds 300° F. In oil & gas wireline logging applications, the heat sensitive components can be thermally protected inside a Dewar vacuum flask that includes one or two thermal isolators and heat sinks. Cooler electronic components results in longer logging times that lead to a much higher performance and profitability. This paper first discusses the development of a one-dimensional analytical model to determine the transient temperature of heat sensitive sensors and electronic components in wireline logging tools. Second, it introduces a new and improved thermal packaging scheme based on a newly developed and commercially available nanoporous material. This material has a very low thermal conductivity and is used as a thermal shield between the outside environment and the electronics inside the flask. The new packaging scheme also includes a new design for the heat sink which is made of several solid disks separated by this nanoporous material. Results from this new design have shown roughly a 30% improvement compared with the conventional design. Results from both analytical and laboratory tests are discussed in this paper.

Experimental Validation of the COMPACT Code in Data Centers

2010 ◽  
Author(s):  
Michael M. Toulouse ◽  
David Lettieri ◽  
Van P. Carey ◽  
Cullen E. Bash
Keyword(s):  
Data Center ◽  
Potential Flow ◽  
Data Centers ◽  
Sparse Matrix ◽  
Convective Transport ◽  
Design Tool ◽  
Compact Model ◽  
Measured Temperature ◽  
Flow Phenomena ◽  
Energy Equations

This paper summarizes the comparison of predictions by a compact model of air flow and transport in data centers to temperature measurements of an operational data center. The simplified model and code package, referred to as COMPACT (Compact Model of Potential Flow and Convective Transport), is intended as an alternative to the use of time-intensive full CFD thermofluidic models as a first-order design tool, as well as a potential improvement to plant-based controllers. COMPACT is based on potential flow and combined with an application of convective energy equations, using sparse matrix solvers to seek flow and temperature solutions. Full-room solutions can be generated in 15 seconds on a commercially available laptop, and an accompanying graphical user interface has also been developed to allow quick configuration of data center designs and analysis of flow and temperature results. Experiments for validation of the model were conducted at the HP Labs data center in Palo Alto, CA, which is in a traditional configuration consisting of inlet floor tiles feeding cold air between two rows of multiple server racks. Subsequently, air exits either through ceiling tiles or direct room-return to CRAC units located on the side of the room. Temperatures were recorded at multiple points along entering and exiting flow faces within the room, as well as at various points in cold and hot aisles, and are presented and compared to model predictions to assess their accuracy. Areas of greater and lesser accuracy are analyzed and presented, in addition to conclusions as to the strengths and weaknesses of the model. For some cases, the average predicted temperature along in-flowing rack faces was within one degree of the average measured temperature. However, the differences in temperature are not evenly distributed. The most pronounced variations between the model and room measurements were located in areas above server racks where recirculation was shown to most likely occur. In these areas, the predicted temperature was higher than experimental values; this can likely be attributed to the absence of buoyancy effects in the simplified potential flow model. Adaptations of the model and its configuration standards for more accurate temperature distributions are proposed, as well as investigations into the effect on temperature comparisons to idealized model output by unaccounted heat sources or flow phenomena.

Research on Intelligent Air Conditioning System of Data Center

2014 ◽  
Vol 602-605 ◽  
pp. 928-932
Author(s):  
Min Li ◽  
Yun Wang ◽  
Zheng Qian Feng ◽  
Wang Li
Keyword(s):  
Heat Exchange ◽  
Energy Saving ◽  
Data Center ◽  
Air Conditioning ◽  
Data Centers ◽  
Cooling Efficiency ◽  
Exchange System ◽  
Air Conditioning System ◽  
Running Time ◽  
Heat Exchange System

By studying the energy-saving technologies of air-conditioning system in data centers, we designed a intelligent air conditioning system, improved the cooling efficiency of air conditioning system through a reasonable set of hot and cold aisles, reduced the running time of HVAC by using the intelligent heat exchange system, an provided a reference for energy saving research of air conditioning system of data centers.

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