Laser amplification in an Yb : YAG active mirror with a significant temperature gradient

2021 ◽  
Vol 51 (8) ◽  
pp. 679-682
Author(s):  
G V Kuptsov ◽  
V A Petrov ◽  
Viktor Valerievich Petrov ◽  
A V Laptev ◽  
A O Konovalova ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Laser Amplification ◽  
Significant Temperature ◽  
Active Mirror

scholarly journals The ‘Isothermal’ Phase of Nova Dust Shells

1983 ◽  
Vol 72 ◽  
pp. 133-138
Author(s):  
R.M. Mitchel ◽  
A. Evans ◽  
M.F. Bode
Keyword(s):  
Grain Size ◽  
Temperature Gradient ◽  
Infrared Spectrum ◽  
Grain Growth ◽  
Optical Depth ◽  
Effective Temperature ◽  
Near Infrared ◽  
Dust Shell ◽  
Consistent Picture ◽  
Significant Temperature

AbstractWe describe a model for the evolution of the infrared spectrum of the dust shell of nova NQ Vul. The effects of nucleation and grain growth, together with.extended, but diminishing, mass loss from the nova, are included. The variations in the effective temperature of the dust shell that occur near infrared maximum may be understood in terms of varying optical depth in a dust shell having significant temperature gradient. However, a more consistent picture is shown to combine interrelated optical depth and grain size variations.

Transverse Temperature Gradient Effect on Fin Efficiency for Micro-Channel Design

2001 ◽  
Vol 123 (4) ◽  
pp. 344-350 ◽  
Author(s):  
Mohamed-Nabil Sabry
Keyword(s):  
Temperature Gradient ◽  
Channel Length ◽  
Accurate Estimation ◽  
Micro Channel ◽  
Cooling Fluid ◽  
Fin Efficiency ◽  
Cooling Method ◽  
Micro Channels ◽  
Significant Temperature ◽  
Transverse Temperature

Heat transfer in micro-channels, used as an efficient cooling method for electronic circuits, is revisited. Channel walls act as a fin conveying heat to the cooling fluid. The relatively low amount of fluid circulating and high micro-channel length-to-depth ratio will cause a significant temperature rise in the fluid between inlet and outlet. This will create a transverse temperature gradient normal to the prevailing temperature gradient in the channel walls. This 2D problem will be analytically solved for laminar incompressible flow with constant physical properties in order to get an accurate estimation of the fin efficiency subject to a 2D field of temperature difference.

Heat transfer to a slowly moving fluid from a dilute fixed bed of heated spheres

1980 ◽  
Vol 101 (2) ◽  
pp. 403-421 ◽  
Author(s):  
A. Acrivos ◽  
E. J. Hinch ◽  
D. J. Jeffrey
Keyword(s):  
Temperature Gradient ◽  
Volume Fraction ◽  
Fixed Bed ◽  
Spherical Particles ◽  
Excess Temperature ◽  
Bulk Heating ◽  
Averaged Equations ◽  
Significant Temperature ◽  
The Difference ◽  
Sufficient Magnitude

Using the method of averaged equations, we examine the difference in temperature between the bulk and fixed heated spherical particles under conditions in which ϕ the volume fraction of the particles and ε the Peclet number of the flow past the particles are both small. If ϕ [Lt ] ε2 the particles are effectively isolated, and so their excess temperature has an O(ε) correction to the pure conduction estimate. On the other hand if ϕ [Gt ] ε2, the bulk heating is of sufficient magnitude to produce a significant temperature gradient throughout the fixed bed. This temperature gradient leads to an O(ϕ½) correction to the pure conduction estimate of the excess temperature of the particles, and the correction depends on the details of the flow even though its magnitude is independent of ε. A study of the leading-order terms when ϕ and ε2 are of the same magnitude finds that the two small effects are not simply additive.

scholarly journals Strain response and energy dissipation of floating saline ice under cyclic compressive stress

2020 ◽  
Vol 14 (9) ◽  
pp. 2849-2867
Author(s):  
Mingdong Wei ◽  
Arttu Polojärvi ◽  
David M. Cole ◽  
Malith Prasanna
Keyword(s):  
Energy Dissipation ◽  
Cyclic Loading ◽  
Temperature Gradient ◽  
Sea Ice ◽  
Compressive Loading ◽  
Cyclic Stress ◽  
Naturally Occurring ◽  
Physically Based ◽  
Constitutive Response ◽  
Significant Temperature

Abstract. Understanding the mechanical behavior of sea ice is the basis of applications of ice mechanics. Laboratory-scale work on saline ice has often involved dry, isothermal ice specimens due to the relative ease of testing. This approach does not address the fact that the natural sea ice is practically always floating in seawater and typically has a significant temperature gradient. To address this important issue, we have developed equipment and methods for conducting compressive loading experiments on floating laboratory-prepared saline ice specimens. The present effort describes these developments and presents the results of stress-controlled sinusoidal cyclic compression experiments. We conducted the experiments on dry, isothermal (−10 ∘C) ice specimens and on floating-ice specimens with a naturally occurring temperature gradient. The experiments involved ice salinities of 5 and 7 ppt, cyclic stress levels ranging from 0.04–0.12 to 0.08–0.25 MPa and cyclic loading frequencies of 0.001 to 1 Hz. The constitutive response and energy dissipation under cyclic loading were successfully analyzed using an existing physically based constitutive model for sea ice. The results highlight the importance of testing warm and floating-ice specimens and demonstrate that the experimental method proposed in this study provides a convenient and practical approach to perform laboratory experiments on floating ice.

scholarly journals Thermal Gradient Mechanical Fatigue Assessment of a Nickel-Based Superalloy

2019 ◽  
Vol 300 ◽  
pp. 07004
Author(s):  
Huang Yuan ◽  
Jingyu Sun
Keyword(s):  
Temperature Gradient ◽  
Thermal Gradient ◽  
Correction Term ◽  
Heating System ◽  
Thermal Gradients ◽  
Mechanical Fatigue ◽  
Nickel Based Superalloy ◽  
Internally Cooled ◽  
Significant Temperature ◽  
Gradient Effects

Turbine components generally work under thermomechanical loading conditions with varying temperature and significant temperature gradients. In the present work, a radiation heating system was developed to simulate thermal gradient mechanical fatigue (TGMF) loads in turbines. The specimen is externally heated by radiation and internally cooled by compressed air. Experiments showed that the TGMF life of the nickel-based superalloy is significantly shorter than that of the thermomechanical and the isothermal fatigue, although the thermal stress amplitude related to the temperature gradient is small. It was confirmed that the conventional fatigue models generated seriously deviations and could not catch effects of thermal gradients. The modified TGMF model introduced a correction term of the temperature gradient effects and can describe the TGMF lifetime of Inconel 718 reasonably. The new model provides a uniform description of isothermal and complex thermomechanical fatigue.

scholarly journals Strain response and energy dissipation of floating saline ice under cyclic compressive stress

2020 ◽  
Author(s):  
Mingdong Wei ◽  
Arttu Polojärvi ◽  
David M. Cole ◽  
Malith Prasanna
Keyword(s):  
Energy Dissipation ◽  
Cyclic Loading ◽  
Temperature Gradient ◽  
Sea Ice ◽  
Compressive Loading ◽  
Cyclic Stress ◽  
Naturally Occurring ◽  
Physically Based ◽  
Constitutive Response ◽  
Significant Temperature

Abstract. Understanding the mechanical behavior of sea ice is the basis of ice mechanics applications. Laboratory-scale work on saline ice has often involved dry, isothermal ice specimens due to the relative ease of testing. This approach does not address the fact that the natural sea ice is practically always floating in seawater and typically has a significant temperature gradient. To address this important issue, we have developed equipment and methods for conducting compressive loading experiments on floating laboratory-prepared saline ice specimens. The present effort describes these developments and presents the results of stress-controlled cyclic compression experiments. We conducted the experiments on dry, isothermal (−10 °C) ice specimens and on floating ice specimens with a naturally occurring temperature gradient. The experiments involved ice salinities of 5 and 7 ppt, cyclic stress levels ranging from 0.04–0.12 MPa to 0.08–0.25 MPa and cyclic loading frequencies of 10−3 Hz to 1 Hz. The constitutive response and energy dissipation under cyclic loading were successfully analyzed using an existing physically based constitutive model for sea ice. The results highlight the importance of testing warm and floating ice specimens and demonstrate that the experimental method proposed in this study provides a convenient and practical approach to perform laboratory experiments on floating ice.

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