Desiccation behaviour of composite landfill lining systems under thermal gradients

The swelling of irradiated UO2 has been attributed to the migration and agglomeration of fission gas bubbles in a thermal gradient. High temperatures and thermal gradients obtained by electron beam heating simulate reactor behavior and lead to the postulation of swelling mechanisms. Although electron microscopy studies have been reported on UO2, two experimental procedures have limited application of the results: irradiation was achieved either with a stream of inert gas ions without fission or at depletions less than 2 x 1020 fissions/cm3 (∼3/4 at % burnup). This study was not limited either of these conditions and reports on the bubble characteristics observed by transmission and fractographic electron microscopy in high density (96% theoretical) UO2 irradiated between 3.5 and 31.3 x 1020 fissions/cm3 at temperatures below l600°F. Preliminary results from replicas of the as-polished and etched surfaces of these samples were published.

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BOILING HEAT TRANSFER ENHANCEMENT ON STRUCTURED SURFACES WITH ENGINEERED THERMAL GRADIENTS AND NUCLEATION SITES

Proceeding of First Thermal and Fluids Engineering Summer Conference ◽

10.1615/tfesc1.mph.012980 ◽

2016 ◽

Author(s):

Md Mahamudur Rahman ◽

Emre Olceroglu ◽

Matthew McCarthy

Keyword(s):

Heat Transfer ◽

Heat Transfer Enhancement ◽

Boiling Heat Transfer ◽

Thermal Gradients ◽

Transfer Enhancement ◽

Structured Surfaces ◽

Nucleation Sites

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Assessment of thermal behavior of a cooling system to reduce thermal fatigue cracks in aluminum injection molds

Revista Liberato ◽

10.31514/rliberato.2020v21n35.p75 ◽

2020 ◽

pp. 75-86

Author(s):

Sergio Antonio Camargo ◽

Lauro Correa Romeiro ◽

Carlos Alberto Mendes Moraes

Keyword(s):

Thermal Fatigue ◽

Cooling System ◽

Fatigue Cracks ◽

Cooling Water ◽

Thermal Conditions ◽

Thermal Gradients ◽

Ansys Software ◽

Cooling Systems ◽

Thermal Fatigue Cracks ◽

Number Of Cycles

The present article aimed to test changes in cooling water temperatures of males, present in aluminum injection molds, to reduce failures due to thermal fatigue. In order to carry out this work, cooling systems were studied, including their geometries, thermal gradients and the expected theoretical durability in relation to fatigue failure. The cooling system tests were developed with the aid of simulations in the ANSYS software and with fatigue calculations, using the method of Goodman. The study of the cooling system included its geometries, flow and temperature of this fluid. The results pointed to a significant increase in fatigue life of the mold component for the thermal conditions that were proposed, with a significant increase in the number of cycles, to happen failures due to thermal fatigue.

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Toward living nanomachines

10.1093/oso/9780199674923.003.0039 ◽

2018 ◽

Author(s):

Christof Mast ◽

Friederike Möller ◽

Moritz Kreysing ◽

Severin Schink ◽

Benedikt Obermayer ◽

...

Keyword(s):

Molecular Evolution ◽

Thermal Gradient ◽

Molecular Level ◽

Minimal System ◽

Thermal Gradients ◽

Temperature Oscillations ◽

Fluid Convection ◽

Inanimate Matter ◽

High Concentrations ◽

Periodic Temperature

How does inanimate matter become transformed into animate matter? Living systems evolve by replication and selection at the molecular level and this chapter considers how to establish a synthetic, minimal system that can support molecular evolution and thus life. Molecular evolution cannot be explained by starting with high concentrations of activated chemicals that react toward their chemical equilibrium; persistent non-equilibria are required to maintain continuous reactivity and we especially consider thermal gradients as an early driving force for Darwinian molecular evolution. The temperature difference across water-filled compartments implements a laminar fluid convection with periodic temperature oscillations that allow for the melting and replication of DNA. Simultaneously, dissolved molecules are moved along the thermal gradient by an effect called thermophoresis. The combined result is an efficient molecule trap that exponentially favors long over short DNA and thus maintains complexity. Future experiments will reveal how thermal gradients could actively drive the Darwinian process of replication and selection.

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The effect of thermal gradients on adsorption

Fuel ◽

10.1016/j.fuel.2021.120553 ◽

2021 ◽

Vol 295 ◽

pp. 120553

Author(s):

Marcelle B.M. Spera ◽

Luís F.M. Franco

Keyword(s):

Thermal Gradients

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Simulation of the Evolutions in Real Microstructure of Material under Thermal Cycle with High Thermal Gradients

Procedia CIRP ◽

10.1016/j.procir.2020.01.149 ◽

2020 ◽

Vol 95 ◽

pp. 238-243

Author(s):

T. Bergs ◽

M. Mohammadnejad ◽

R. Hess ◽

L. Heidemanns ◽

A. Klink

Keyword(s):

Thermal Cycle ◽

Thermal Gradients ◽

Microstructure Of Material

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Contactless and spatially structured cooling by directing thermal radiation

Scientific Reports ◽

10.1038/s41598-021-95606-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Nicola M. Kerschbaumer ◽

Stefan Niedermaier ◽

Theobald Lohmüller ◽

Jochen Feldmann

Keyword(s):

Thermal Radiation ◽

Radiative Heat ◽

Radiative Cooling ◽

View Factor ◽

Temperature Pattern ◽

Thermal Gradients ◽

Science And Engineering ◽

Building Management ◽

Temperature Manipulation ◽

Novel Concept

AbstractIn recent years, radiative cooling has become a topic of considerable interest for applications in the context of thermal building management and energy saving. The idea to direct thermal radiation in a controlled way to achieve contactless sample cooling for laboratory applications, however, is scarcely explored. Here, we present an approach to obtain spatially structured radiative cooling. By using an elliptical mirror, we are able to enhance the view factor of radiative heat transfer between a room temperature substrate and a cold temperature landscape by a factor of 92. A temperature pattern and confined thermal gradients with a slope of ~ 0.2 °C/mm are created. The experimental applicability of this spatially structured cooling approach is demonstrated by contactless supercooling of hexadecane in a home-built microfluidic sample. This novel concept for structured cooling yields numerous applications in science and engineering as it provides a means of controlled temperature manipulation with minimal physical disturbance.

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Natural frequency analysis of a functionally graded rotor-bearing system with a slant crack subjected to thermal gradients

International Journal of Turbo and Jet Engines ◽

10.1515/tjj-2021-0002 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Arnab Bose ◽

Prabhakar Sathujoda ◽

Giacomo Canale

Keyword(s):

Finite Element Analysis ◽

Finite Element ◽

Power Law ◽

Beam Theory ◽

Functionally Graded ◽

Thermal Gradients ◽

Element Analysis ◽

Rotor Bearing ◽

Natural Frequency Analysis ◽

Bearing System

Abstract The present work aims to analyze the natural and whirl frequencies of a slant-cracked functionally graded rotor-bearing system using finite element analysis for the flexural vibrations. The functionally graded shaft is modelled using two nodded beam elements formulated using the Timoshenko beam theory. The flexibility matrix of a slant-cracked functionally graded shaft element has been derived using fracture mechanics concepts, which is further used to develop the stiffness matrix of a cracked element. Material properties are temperature and position-dependent and graded in a radial direction following power-law gradation. A Python code has been developed to carry out the complete finite element analysis to determine the Eigenvalues and Eigenvectors of a slant-cracked rotor subjected to different thermal gradients. The analysis investigates and further reveals significant effect of the power-law index and thermal gradients on the local flexibility coefficients of slant-cracked element and whirl natural frequencies of the cracked functionally graded rotor system.

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