Data center crossflow heat exchanger study under different transient temperature boundary conditions

2014 ◽  
Author(s):  
Tianyi Gao ◽  
Bahgat Sammakia ◽  
Bruce Murray ◽  
Alfonso Ortega ◽  
Roger Schmidt
Keyword(s):  
Heat Exchanger ◽  
Boundary Conditions ◽  
Data Center ◽  
Transient Temperature ◽  
Temperature Boundary

Thermomechanical Design of a Heat Exchanger for a Recuperative Aeroengine

2006 ◽  
Vol 128 (4) ◽  
pp. 736-744 ◽  
Author(s):  
Harald Schoenenborn ◽  
Ernst Ebert ◽  
Burkhard Simon ◽  
Paul Storm
Keyword(s):  
Thermal Analysis ◽  
Heat Exchanger ◽  
Boundary Conditions ◽  
Stress Analysis ◽  
Element Model ◽  
Automatic Generation ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Engine Operation ◽  
Aero Engines

Within the framework programs of the EU for Efficient and Environmentally Friendly Aero-Engines (EEFEA) MTU has developed a highly efficient cross-counter flow heat exchanger for the application in intercooled recuperated aeroengines. This very compact recuperator is based on the profile tube matrix arrangement invented by MTU and one of its outstanding features is the high resistance to thermal gradients. In this paper the combined thermomechanical design of the recuperator is presented. State-of-the-art calculation procedures for heat transfer and stress analysis are combined in order to perform a reliable life prediction of the recuperator. The thermal analysis is based upon a 3D parametric finite element model generation. A program has been generated, which allows the automatic generation of both the material mesh and the boundary conditions. Assumptions concerning the boundary conditions are presented as well as steady state and transient temperature results. The stress analysis is performed with a FEM code using essentially the same computational grid as the thermal analysis. With the static temperature fields the static loading of the profile tubes is determined. From transient thermal calculations successive 3D temperature fields are obtained which enable the determination of creep life and LCF life of the part. Finally, vibration analysis is performed in order to estimate the vibration stress of the profile tubes during engine operation. Together with the static stress a Goodman diagram can be constructed. The combined analysis shows the high life potential of the recuperator, which is important for economic operation of a recuperative aero-engine.

Thermomechanical Design of a Heat Exchanger for a Recuperative Aero Engine

2004 ◽  
Author(s):  
Harald Scho¨nenborn ◽  
Ernst Ebert ◽  
Burkhard Simon ◽  
Paul Storm
Keyword(s):  
Thermal Analysis ◽  
Heat Exchanger ◽  
Boundary Conditions ◽  
Stress Analysis ◽  
Automatic Generation ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Engine Operation ◽  
Aero Engine ◽  
Aero Engines

Within the framework programs of the EU for Efficient and Environmentally Friendly Aero-Engines (EEFEA) MTU has developed a highly efficient cross-counter flow heat exchanger for the application in intercooled recuperated aero-engines. This very compact recuperator is based on the profile tube matrix arrangement invented by MTU and one of its outstanding features is the high resistance to thermal gradients. In this paper the combined thermomechanical design of the recuperator is presented. State-of-the-art calculation procedures for heat transfer and stress analysis are combined in order to perform a reliable life prediction of the recuperator. The thermal analysis is based upon a 3D parametric finite element model generation. A program has been generated, which allows the automatic generation of both the material mesh and the boundary conditions. Assumptions concerning the boundary conditions are presented as well as steady state and transient temperature results. The stress analysis is performed with a FEM code using essentially the same computational grid as the thermal analysis. With the static temperature fields the static loading of the profile tubes is determined. From transient thermal calculations successive 3D temperature fields are obtained which enable the determination of creep life and LCF life of the part. Finally, vibration analysis is performed in order to estimate the vibration stress of the profile tubes during engine operation. Together with the static stress a Goodman diagram can be constructed. The combined analysis shows the high life potential of the recuperator, which is important for economic operation of a recuperative aero-engine.

scholarly journals Inhomogeneous Temperature Distribution Affecting the Cyclic Aging of Li-Ion Cells. Part II: Analysis and Correlation

Batteries ◽  
2020 ◽  
Vol 6 (1) ◽  
pp. 12 ◽  
Author(s):  
Daniel Werner ◽  
Sabine Paarmann ◽  
Achim Wiebelt ◽  
Thomas Wetzel
Keyword(s):  
Boundary Conditions ◽  
Lithium Ion ◽  
Temperature Gradients ◽  
Transient Temperature ◽  
Aging Behavior ◽  
Thermal Boundary Conditions ◽  
Temperature Boundary ◽  
Inhomogeneous Temperature ◽  
Temperature Levels ◽  
Definition Of

Temperature has a significant influence on the behavior of batteries and their lifetime. There are several studies in literature that investigate the aging behavior under electrical load, but are limited to homogeneous, constant temperatures. This article presents an approach to quantifying cyclic aging of lithium-ion cells that takes into account complex thermal boundary conditions. It not only considers different temperature levels but also spatial and transient temperature gradients that can occur despite-or even due to-the use of thermal management systems. Capacity fade and impedance rise are used as measured quantities for degradation and correlated with the temperature boundary conditions during the aging process. The concept and definition of an equivalent aging temperature (EAT) is introduced to relate the degradation caused by spatial and temporal temperature inhomogeneities to similar degradation caused by a homogeneous steady temperature during electrical cycling. The results show an increased degradation at both lower and higher temperatures, which can be very well described by two superimposed exponential functions. These correlations also apply to cells that are cycled under the influence of spatial temperature gradients, both steady and transient. Only cells that are exposed to transient, but spatially homogeneous temperature conditions show a significantly different aging behavior. The concluding result is a correlation between temperature and aging rate, which is expressed as degradation per equivalent full cycle (EFC). This enables both temperature-dependent modeling of the aging behavior and its prediction.

Sidewall finite-conductivity effects in confined turbulent thermal convection

2002 ◽  
Vol 473 ◽  
pp. 201-210 ◽  
Author(s):  
ROBERTO VERZICCO
Keyword(s):  
Boundary Conditions ◽  
Thermal Convection ◽  
Lateral Wall ◽  
Finite Conductivity ◽  
Mean Flow ◽  
Number Range ◽  
Additional Heat ◽  
Low Aspect Ratio ◽  
Temperature Boundary ◽  
The Mean

The effects of a sidewall with finite thermal conductivity on confined turbulent thermal convection has been investigated using direct numerical simulation. The study is motivated by the observation that the heat flowing through the lateral wall is not always negligible in the low-aspect-ratio cells of several recent experiments. The extra heat flux modifies the temperature boundary conditions of the flow and therefore the convective heat transfer. It has been found that, for usual sidewall thicknesses, the heat travelling from the hot to the cold plates directly through the sidewall is negligible owing to the additional heat exchanged at the lateral fluid/wall interface. In contrast, the modified temperature boundary conditions alter the mean flow yielding significant Nusselt number corrections which, in the low Rayleigh number range, can change the exponent of the Nu vs. Ra power law by 10%.

Heat and Mass Transfer to Air in a Cross Flow Heat Exchanger with Surface Deluge Cooling

2016 ◽  
Vol 24 (01) ◽  
pp. 1650002 ◽  
Author(s):  
Andrea Diani ◽  
Luisa Rossetto ◽  
Roberto Dall’Olio ◽  
Daniele De Zen ◽  
Filippo Masetto
Keyword(s):  
Heat Exchanger ◽  
Heat Flow ◽  
Flow Rate ◽  
Data Center ◽  
Heat Dissipation ◽  
Cross Flow ◽  
Critical Conditions ◽  
Heat Flow Rate ◽  
External Temperature ◽  
Flow Heat

Cross flow heat exchangers, when applied to cool data center rooms, use external air (process air) to cool the air stream coming from the data center room (primary air). However, an air–air heat exchanger is not enough to cope with extreme high heat loads in critical conditions (high external temperature). Therefore, water can be sprayed in the process air to increase the heat dissipation capability (wet mode). Water evaporates, and the heat flow rate is transferred to the process air as sensible and latent heat. This paper proposes an analytical approach to predict the behavior of a cross flow heat exchanger in wet mode. The theoretical results are then compared to experimental tests carried out on a real machine in wet mode conditions. Comparisons are given in terms of calculated versus experimental heat flow rate and evaporated water mass flow rate, showing a good match between theoretical and experimental values.

Prediction of Hot Aisle Partition Airflow Boundary Conditions

2013 ◽  
Author(s):  
Zhihang Song ◽  
Bruce T. Murray ◽  
Bahgat Sammakia
Keyword(s):  
Boundary Conditions ◽  
Data Center ◽  
Computation Time ◽  
Design Tool ◽  
Operating Conditions ◽  
Ann Model ◽  
Flow Rates ◽  
Level Model ◽  
Optimization Methodology ◽  
Artificial Neural Network Ann

The integration of a simulation-based Artificial Neural Network (ANN) with a Genetic Algorithm (GA) has been explored as a real-time design tool for data center thermal management. The computation time for the ANN-GA approach is significantly smaller compared to a fully CFD-based optimization methodology for predicting data center operating conditions. However, difficulties remain when applying the ANN model for predicting operating conditions for configurations outside of the geometry used for the training set. One potential remedy is to partition the room layout into a finite number of characteristic zones, for which the ANN-GA model readily applies. Here, a multiple hot aisle/cold aisle data center configuration was analyzed using the commercial software FloTHERM. The CFD results are used to characterize the flow rates at the inter-zonal partitions. Based on specific reduced subsets of desired treatment quantities from the CFD results, such as CRAC and server rack air flow rates, the approach was applied for two different CRAC configurations and various levels of CRAC and server rack flow rates. Utilizing the compact inter-zonal boundary conditions, good agreement for the airflow and temperature distributions is achieved between predictions from the CFD computations for the entire room configuration and the reduced order zone-level model for different operating conditions and room layouts.

A Method for Applying Automatic Temperature Control to the Transient Finite Element Analysis of a Pressure Vessel Undergoing Postweld Heat Treatment

2004 ◽  
Author(s):  
Michael Sciascia
Keyword(s):  
Heat Treatment ◽  
Finite Element ◽  
Boundary Conditions ◽  
Temperature Profile ◽  
Pressure Vessel ◽  
Postweld Heat Treatment ◽  
Transient Temperature ◽  
Element Analysis ◽  
Heater Power ◽  
Postweld Heat

For complex finite element problems it is often desirable to prescribe boundary conditions that are difficult to quantify. The analysis of a pressure vessel undergoing postweld heat treatment (PWHT) is an example of such a problem. The PWHT process is governed by Code rules, but the temperature and gradient requirements they impose are not sufficient to precisely describe the complete vessel temperature profile. The imposition of such a profile in the analysis results in uncertainty and errors. A suitable but difficult approach is to specify heater power instead of temperatures, letting the solver determine the temperature profile. Unfortunately, the individual heater power levels necessary to meet the Code requirements are usually not known in advance. Determining the power levels necessary is particularly difficult if a transient solution is required. A means of actively controlling the heaters during the FEA solution is requirement for this approach. A simple and adaptive control algorithm was incorporated into the FEA solver via its scripting capability. Heat flux boundary conditions (heater power) were applied instead of transient temperature boundary conditions. Heater power levels were optimized to achieve predetermined time/temperature goals as the solution proceeded. The algorithm described was successfully applied to a pressure vessel PWHT with 14 zones of control. The approach may be adapted to other problems and boundary conditions.

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