scholarly journals Numerical Analysis on Temperature Rise of a Concrete Arch Dam after Sealing Based on Measured Data

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Qingbin Li ◽  
Guohe Liang ◽  
Yu Hu ◽  
Zheng Zuo
Keyword(s):  
Boundary Conditions ◽  
Temperature Rise ◽  
Internal Heat ◽  
Arch Dam ◽  
External Boundary ◽  
Measured Temperature ◽  
External Temperature ◽  
Concrete Arch Dam ◽  
Thermal Boundary Conditions ◽  
Environment Temperature

The thermal boundary conditions in the construction and operation phases of a concrete arch dam are always complex. After sealing, differences between the arch dam temperature and its sealing temperature can cause compressive or tensile stresses. Based on measured temperature of an arch dam located in China, a temperature rise phenomenon (TRP) is found in the after-sealed regions of the arch dam. By mining and analyzing the temperature data of various monitoring apparatus embedded in the arch dam, higher environment temperature is considered to be the main cause for the occurrence of the TRP. Mathematical methods for complex thermal boundary conditions, including external boundary conditions and internal heat source conditions, are proposed in this paper. A finite element model is implemented with the concern of the construction phase and operation phase of the arch dam. Results confirm good agreement with the measured temperature and verify the conjecture that the TRP occurs mainly because the external temperature of the arch dam is higher than its sealing temperature.

scholarly journals Inhomogeneous Temperature Distribution Affecting the Cyclic Aging of Li-Ion Cells. Part I: Experimental Investigation

Batteries ◽  
2020 ◽  
Vol 6 (1) ◽  
pp. 13 ◽  
Author(s):  
Daniel Werner ◽  
Sabine Paarmann ◽  
Achim Wiebelt ◽  
Thomas Wetzel
Keyword(s):  
Boundary Conditions ◽  
Heat Dissipation ◽  
Single Cells ◽  
Internal Heat ◽  
Lithium Ion ◽  
Ambient Air ◽  
Substantial Impact ◽  
Temperature Changes ◽  
Thermal Boundary Conditions ◽  
Cyclic Degradation

Alongside electrical loads, it is known that temperature has a strong influence on battery behavior and lifetime. Investigations have mainly been performed at homogeneous temperatures and non-homogeneous conditions in single cells have at best been simulated. This publication presents the development of a methodology and experimental setup to investigate the influence of thermal boundary conditions during the operation of lithium-ion cells. In particular, spatially inhomogeneous and transient thermal boundary conditions and periodical electrical cycles were superimposed in different combinations. This required a thorough design of the thermal boundary conditions applied to the cells. Unlike in other contributions that rely on placing cells in a climatic chamber to control ambient air temperature, here the cell surfaces and tabs were directly connected to individual cooling and heating plates. This improves the control of the cells’ internal temperature, even with high currents accompanied by strong internal heat dissipation. The aging process over a large number of electrical cycles is presented by means of discharge capacity and impedance spectra determined in repeated intermediate characterizations. The influence of spatial temperature gradients and temporal temperature changes on the cyclic degradation is revealed. It appears that the overall temperature level is indeed a decisive parameter for capacity fade during cyclic aging, while the intensity of a temperature gradient is not as essential. Furthermore, temperature changes can have a substantial impact and potentially lead to stronger degradation than spatial inhomogeneities.

scholarly journals Temperature Field Online Reconstruction for In-Service Concrete Arch Dam Based on Limited Temperature Observation Data Using AdaBoost-ANN Algorithm

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zhuoyan Chen ◽  
Dongjian Zheng ◽  
Jiqiong Li ◽  
Xin Wu ◽  
Jianchun Qiu
Keyword(s):  
Finite Element ◽  
Temperature Field ◽  
Temperature Data ◽  
Arch Dam ◽  
Observation Data ◽  
Measured Temperature ◽  
Concrete Arch Dam ◽  
Temperature Observation ◽  
Limited Temperature ◽  
Online Reconstruction

Temperature is one of the factors affecting the safety operation of concrete arch dams. To accurately reconstruct the temperature field of the concrete arch dam online based on the temperature data of several typical dam sections, this paper proposes the AdaBoost-ANN algorithm. The algorithm uses artificial neural network (ANN) to establish a training set of the measured temperature data and the temperature field of the concrete arch dam obtained by the three-dimensional finite element model; these trained artificial neural networks are used as weak classifiers of the AdaBoost algorithm. Then, the AdaBoost-ANN algorithm is used to establish the mapping relationship between the measured temperature data and the temperature field, and the online reconstruction of the temperature field of the concrete arch dam is realized. The case study shows that the temperature field of the concrete arch dam can be accurately established by AdaBoost-ANN algorithm based on limited temperature observation data. The algorithm is more time-saving and labor-saving than the finite element method and is convenient for online reconstruction of the temperature field and assessment of the safety status of the concrete arch dam.

Experimental Investigation of Heat Transfer Dependency on Conjugate and Convective Thermal Boundary Conditions in Pin Fin Channel

2015 ◽  
Author(s):  
Weihong Li ◽  
Zhongran Chi ◽  
Rui Kan ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Boundary Conditions ◽  
Internal Wall ◽  
External Temperature ◽  
External Wall ◽  
Pin Fin ◽  
Thermal Boundary Conditions ◽  
Temperature Distributions ◽  
Pin Fin Arrays

The present work experimentally quantifies the effects of thermal boundary conditions, i.e., conjugate and convective boundary conditions, on heat transfer performance for the pin fin channel in trailing edge of gas turbine blade. The geometry of pin fin arrays is typical of x/D=y/D=2.5 and H/D=1. For conjugate case, model is constructed with a relatively high conductivity material so that the Biot number of the model matches engine condition. Uniform heat flux is imposed along the external wall of pin fin arrays and highly resolved temperature distributions of internal wall is obtained with steady liquid crystal, meanwhile external temperature is measured through thermocouples. For convective case, model is constructed with low thermal conductivity material to ensure the usage of transient liquid crystal to obtain heat transfer coefficients of the internal wall on the same configuration. Both the measurements are used as boundary conditions to conduct simulation of solid part of pin fin array. Internal and external wall non-dimensional temperature distributions, as well as isothermal lines distribution, of the two cases are compared, results indicate that it will produce large errors in temperature predictions without considering conjugate effect. Further analysis are made about the mechanism of thermal boundary conditions in determining wall temperature, which demonstrates the necessity of taking conjugate heat transfer effect in turbine cooling design.

Steady Temperatures in a Rotating Cylinder—Some Variations in the Geometry and the Thermal Boundary Conditions

1986 ◽  
Vol 108 (3) ◽  
pp. 446-453 ◽  
Author(s):  
B. Gecim ◽  
W. O. Winer
Keyword(s):  
Boundary Conditions ◽  
Outer Boundary ◽  
Internal Heat ◽  
Critical Factor ◽  
Bulk Temperature ◽  
Surface Boundary ◽  
Heat Sources ◽  
Thermal Boundary Conditions ◽  
Surface Boundary Conditions ◽  
Wide Range

Three cases are studied as variations in the geometry and the thermal boundary conditions pertinent to the classical flash temperature theory. First, the case of multiple surface heat sources is considered. It is shown that the relative location of the sources is the critical factor in predicting the local temperatures at each contact. Second, the case of a short cylinder (or a disk) is analyzed. In addition to the lateral surface boundary conditions, convective cooling from the side faces is considered. It is shown that a considerable reduction in bulk temperature can be achieved by effective cooling from the side faces. Third, the case of a hollow cylinder is studied where, in addition to the outer boundary conditions, uniform internal heating (or cooling) is considered. It is demonstrated that the bulk temperature can be varied significantly by changing the magnitude (and direction) of the internal heat flux. In both the second and the third cases, over a wide range of the pertinent parameters, it is shown that the local temperature rise remains virtually unchanged.

Vibration-based damage detection of a concrete arch dam

2021 ◽  
Vol 235 ◽  
pp. 112032
Author(s):  
Sérgio Pereira ◽  
Filipe Magalhães ◽  
Jorge P. Gomes ◽  
Álvaro Cunha ◽  
José V. Lemos
Keyword(s):  
Damage Detection ◽  
Arch Dam ◽  
Concrete Arch Dam

Modal identification of concrete arch dam by fully automated operational modal identification

Structures ◽  
2021 ◽  
Vol 32 ◽  
pp. 228-236
Author(s):  
Hasan Mostafaei ◽  
Mehdi Ghamami ◽  
Pegah Aghabozorgi
Keyword(s):  
Arch Dam ◽  
Modal Identification ◽  
Concrete Arch Dam
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