Thermal Modeling of a Small-Particle Solar Central Receiver

2000 ◽  
Vol 122 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Fletcher J. Miller ◽  
Roland W. Koenigsdorff
Keyword(s):  
Thermal Model ◽  
Energy Equation ◽  
Three Dimensional ◽  
Temperature Profiles ◽  
Radiation Model ◽  
Carbon Particles ◽  
Temperature Distributions ◽  
Central Receiver ◽  
Type Particle ◽  
Very High

This paper presents a thermal model of a solar central receiver that volumetrically absorbs concentrated sunlight directly in a flowing gas stream seeded with submicron carbon particles. A modified six-flux radiation model is developed and used with the energy equation to calculate the three-dimensional radiant flux and temperature distributions in a cavity-type particle receiver. Results indicate that the receiver is capable of withstanding very high incident fluxes and delivering high temperatures. The receiver efficiency as a function of mass flow rate as well as the effect of particle oxidation on the temperature profiles are presented. [S0199-6231(00)00201-X]

Manipulation of Microfluidic Flows Using Time Dependent Wall Temperatures

2004 ◽  
Author(s):  
Tom Mautner
Keyword(s):  
Thermal Diffusion ◽  
Wall Temperature ◽  
Lattice Boltzmann ◽  
Channel Wall ◽  
Three Dimensional ◽  
Temperature Profiles ◽  
Thermal Coupling ◽  
Uniform Temperature ◽  
Temperature Distributions ◽  
Flow Through

One module in a bioagent detector currently under development involves a flow-through PCR module [1] [3] [4]. Conventional, flow-through PCR devices utilize three heaters to obtain the required temperatures in each zone, the length of which is specified by the required sample residence times. An alternate design uses two wall heaters with substrate conduction supplying the center zone temperature. The concept of using a conduction based PCR device led to an extensive computational study of various channel wall temperature profiles that would produce enhanced mixing in a variety of microfluidic devices. The results are applicable to micro channel designs in general even tough motivated by the conduction based PCR configuration. The lattice Boltzmann (LB) method was used to perform low Reynolds number (typically Re=0.10) simulations for two and three dimensional channel geometries having various wall temperature distributions. The momentum and thermal lattice Boltzmann equations were coupled via a body force term in the momentum equation. Initial computations using two- and three-heater configurations in two dimensions demonstrated excellent comparisons with published data provided that both the top and bottom walls were heated. If only one wall was heated, large vertical thermal gradients occurred resulting in non-uniform temperature fields. However, when the same conditions were applied to three dimensional channels, lower temperatures were observed in the center of the channel regardless of the wall temperatures or channel aspect ratio. Parametric studies were performed to evaluate the effects of thermal coupling, thermal diffusion coefficients, entrance temperatures, wall temperature configurations and channel geometry. If was found that moderate variation of the thermal diffusion coefficient produced only minor differences in the temperature field, and large changes in the thermal coupling magnitude demonstrated transition from natural to forced convection flows. The simulations also indicate that the largest effect on flow and temperature uniformity arises from the applied wall temperature distribution (various thickness channel walls). It was found, in 2D, that if the channel wall starts from ambient temperature, the applied heating, on the outer surfaces only, may not result in the desired wall or fluid temperatures. However, once the channel walls are heated to a uniform temperature, excellent temperature distributions are obtained for both thick and thin channel walls. Additionally, a checkerboard pattern of wall heaters was used to test its application to promoting mixing. Results were favorable in creating enhanced mixing; however, the temperature pattern did not produce uniform temperature profiles in the channel.

Oil-Film Temperature Distribution in an Infinitely wide Slider Bearing: An Application of the Finite-Element Method

1973 ◽  
Vol 15 (4) ◽  
pp. 311-320 ◽  
Author(s):  
A. K. Tieu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Energy Equation ◽  
Three Dimensional ◽  
The Finite Element Method ◽  
Slider Bearing ◽  
Oil Film ◽  
Temperature Distributions ◽  
Oil Films ◽  
Element Method

From the Glansdorff–Prigogine local potential in non-equilibrium thermodynamics (1)† (2), a variational principle for a thin film incompressible flow with viscous dissipation is formulated as the basis of a finite-element method, which is applied to solve the energy equation. Temperature distributions in tapered land and parallel oil films for infinitely wide bearings are obtained by digital computer. The application of the finite-element method in a three-dimensional oil film with side leakage is also discussed.

Effects of Large Blood Vessels on Temperature Distributions During Simulated Cryosurgery

2004 ◽  
Author(s):  
Zhong-Shan Deng ◽  
Jing Liu
Keyword(s):  
Blood Vessels ◽  
Thermal Model ◽  
Energy Equation ◽  
Bioheat Transfer ◽  
Tissue Temperature ◽  
Temperature Distributions ◽  
Complex Heat Transfer ◽  
Transfer Problems ◽  
Temperature Responses ◽  
Capacity Method

Large blood vessels can produce steep temperature gradients in frozen tissues resulting in inadequate cooling temperatures during cryosurgery. In addition, arresting of blood vessels and bleeding due to rupture of large blood vessels by the iceball may cause undesired damage to healthy tissues. However, such important issues received few attentions up to now. In this article, several typical vascular models are applied to study the effects of large blood vessels to the tissue temperature distributions during cryosurgery. The thermal model combines the Pennes bioheat transfer equation describing for perfused tissues and the energy equation for blood vessels. A finite difference algorithm based on the effective heat capacity method is used to solve this complex heat transfer problems. In the algorithm, the tissues are treated as nonideal materials, freezing over a temperature range. Numerical analyses are then performed to study the influences of the blood vessels to the temperature distributions of tissues. The results indicate that different vascular models produce significantly different temperature responses for a given freezing pattern.

Drill Temperature Distributions by Numerical Solutions

1971 ◽  
Vol 93 (4) ◽  
pp. 1057-1066 ◽  
Author(s):  
U. K. Saxena ◽  
M. F. DeVries ◽  
S. M. Wu
Keyword(s):  
Experimental Data ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Analytical Solutions ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Temperature Profiles ◽  
Temperature Distributions ◽  
Drill Cutting ◽  
Drill Point

The backward finite-difference method is used to determine three-dimensional drill temperature distributions. The geometry of the drill was described by (1) approximating the drill as a one-quarter cone and (2) sectioning a true drill point and measuring its profiles. The three-dimensional temperature distributions provided both drill cutting edge and drill flank temperature profiles which were close to prior experimental data and showed improvement over the previous analytical solutions.

Three-dimensional fault geometry and kinematics of the 2008 M 7.1 Yutian earthquake revealed by very-high resolution satellite stereo imagery

2019 ◽  
Vol 232 ◽  
pp. 111300
Author(s):  
Xiaogang Song ◽  
Nana Han ◽  
Xinjian Shan ◽  
Chisheng Wang ◽  
Yingfeng Zhang ◽  
...  
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
Fault Geometry ◽  
Stereo Imagery ◽  
Very High ◽  
Geometry And Kinematics

scholarly journals Shell-crossing in a ΛCDM Universe

2020 ◽  
Vol 501 (1) ◽  
pp. L71-L75
Author(s):  
Cornelius Rampf ◽  
Oliver Hahn
Keyword(s):  
Dark Matter ◽  
Perturbation Theory ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Three Dimensional ◽  
Random Initial Data ◽  
Recursion Relations ◽  
Indispensable Tool ◽  
First Time ◽  
Very High

ABSTRACT Perturbation theory is an indispensable tool for studying the cosmic large-scale structure, and establishing its limits is therefore of utmost importance. One crucial limitation of perturbation theory is shell-crossing, which is the instance when cold-dark-matter trajectories intersect for the first time. We investigate Lagrangian perturbation theory (LPT) at very high orders in the vicinity of the first shell-crossing for random initial data in a realistic three-dimensional Universe. For this, we have numerically implemented the all-order recursion relations for the matter trajectories, from which the convergence of the LPT series at shell-crossing is established. Convergence studies performed at large orders reveal the nature of the convergence-limiting singularities. These singularities are not the well-known density singularities at shell-crossing but occur at later times when LPT already ceased to provide physically meaningful results.

Thermomechanical Coupling of a Hyper-viscoelastic Truck Tire and a Pavement Layer and its Impact on Three-dimensional Contact Stresses

2021 ◽  
pp. 036119812110171
Author(s):  
Angeli Jayme ◽  
Imad L. Al-Qadi
Keyword(s):  
Contact Stress ◽  
Contact Area ◽  
Three Dimensional ◽  
Interaction Model ◽  
Rolling Resistance ◽  
Contact Stresses ◽  
Thermomechanical Coupling ◽  
Temperature Profiles ◽  
Near Surface ◽  
Truck Tire

A thermomechanical coupling between a hyper-viscoelastic tire and a representative pavement layer was conducted to assess the effect of various temperature profiles on the mechanical behavior of a rolling truck tire. The two deformable bodies, namely the tire and pavement layer, were subjected to steady-state-uniform and non-uniform temperature profiles to identify the significance of considering temperature as a variable in contact-stress prediction. A myriad of ambient, internal air, and pavement-surface conditions were simulated, along with combinations of applied tire load, tire-inflation pressure, and traveling speed. Analogous to winter, the low temperature profiles induced a smaller tire-pavement contact area that resulted in stress localization. On the other hand, under high temperature conditions during the summer, higher tire deformation resulted in lower contact-stress magnitudes owing to an increase in the tire-pavement contact area. In both conditions, vertical and longitudinal contact stresses are impacted, while transverse contact stresses are relatively less affected. This behavior, however, may change under a non-free-rolling condition, such as braking, accelerating, and cornering. By incorporating temperature into the tire-pavement interaction model, changes in the magnitude and distribution of the three-dimensional contact stresses were manifested. This would have a direct implication on the rolling resistance and near-surface behavior of flexible pavements.

Anion packing density: a universal quantity for both dense and porous crystalline inorganic phases

2002 ◽  
Vol 58 (3) ◽  
pp. 457-462 ◽  
Author(s):  
F. Liebau ◽  
H. Küppers
Keyword(s):  
High Pressure ◽  
Packing Density ◽  
Three Dimensional ◽  
Ionic Radii ◽  
Generalized Framework ◽  
Molal Volumes ◽  
Definition Of ◽  
Anion Packing ◽  
Very High ◽  
Framework Density

To compare densities of inorganic high-pressure phases their molal volumes or specific gravities are usually employed, whereas for zeolites and other microporous materials the so-called framework density, FD, is applied. The definition of FD, which refers only to phases with three-dimensional tetrahedron frameworks, is extended to a `generalized framework density' d f, which is independent of the dimensionality of the framework and the coordination number(s) of the framework cations. In this paper the anion packing density, d ap, is introduced as a new quantity which is not only applicable to any inorganic phase but, in contrast to FD and d f, also allows quantitative comparisons to be made for crystalline inorganic phases of any kind. The anion packing density can readily be calculated if the volume and content of the unit cell and the radii of the anions of a phase are known. From d ap values calculated for high-pressure silica polymorphs studied under very high pressure, it is concluded that Shannon–Prewitt effective ionic radii do not sufficiently take into account the compressibility of the anions.

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