Computational Modeling of a Solar Thermoelectric Generator

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Chukwunyere Ofoegbu ◽  
Sandip Mazumder
Keyword(s):  
Solar Energy ◽  
Computational Model ◽  
Peak Power ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Atmospheric Conditions ◽  
Absorber Plate ◽  
Thermoelectric Effects ◽  
Order Of Magnitude ◽  
Solar Thermoelectric Generator

Solar thermoelectric generators (STEGs) convert solar energy to electricity. The solar energy is first used to heat an absorber plate that serves as the high temperature reservoir. Power is generated by connecting the hot reservoir and cold (ambient) reservoirs with a pair of p- and n-doped thermoelectric legs. Experimental studies have shown that the efficiency of a STEG can reach values of about 5% if the entire setup is placed in near-vacuum conditions. However, under atmospheric conditions, the efficiency decreases by more than an order of magnitude, presumably due to heat loss from the absorber plate by natural convection. A coupled fluid–thermal–electric three-dimensional computational model of a STEG is developed with the objective of understanding the various loss mechanisms that contribute to its poor efficiency. The governing equations of mass, momentum, energy, and electric current, with the inclusion of thermoelectric effects, are solved on a mesh with 60,900 cells, and the power generated by the device is predicted. The computational model predicts a temperature difference (ΔT) of 16.5 K, as opposed to the experimentally measured value of 15 K. This corresponds to a peak power of 0.031 W as opposed to the experimentally measured peak power of 0.021 W. When only radiative losses are considered (i.e., perfect vacuum), the ΔT increases drastically to 131.1 K, resulting in peak power of 1.43 W. The predicted peak efficiency of the device was found to be 0.088% as opposed to the measured value of 0.058%.

Computational Modeling of a Solar Thermoelectric Generator

2014 ◽  
Author(s):  
Chukwunyere Ofoegbu ◽  
Sandip Mazumder
Keyword(s):  
Solar Energy ◽  
Computational Model ◽  
Peak Power ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Atmospheric Conditions ◽  
Absorber Plate ◽  
Thermoelectric Effects ◽  
Order Of Magnitude ◽  
Solar Thermoelectric Generator

Solar Thermoelectric Generators (STEGs) convert solar energy to electricity. The solar energy is first used to heat an absorber plate that serves as the high temperature reservoir. Power is generated by connecting the hot reservoir and cold (ambient) reservoirs with a pair of p- and n-doped thermoelectric legs. Experimental studies have shown that the efficiency of a STEG can reach values of about 5% if the entire setup is placed in near-vacuum conditions. However, under atmospheric conditions, the efficiency decreases by more than an order of magnitude, presumably due to heat loss from the absorber plate by natural convection. A coupled fluid-thermal-electric three-dimensional computational model of a STEG is developed with the objective of understanding the various loss mechanisms that contribute to its poor efficiency. The governing equations of mass, momentum, energy and electric current, with the inclusion of thermoelectric effects, are solved on a mesh with 60,900 cells, and the power generated by the device is predicted. The computational model predicts a temperature difference (ΔT) of 16.5K, as opposed to the experimentally measured value of 15K. This corresponds to a peak power of 0.031W as opposed to the experimentally measured peak power of 0.021W. When only radiative losses are considered (i.e., perfect vacuum), the ΔT increases drastically to 131.1K, resulting in peak power of 1.43W. The predicted peak efficiency of the device was found to be 0.088% as opposed to the measured value of 0.058%.

Modelling mechanically stable muscle architectures

1992 ◽  
Vol 336 (1277) ◽  
pp. 275-292 ◽  
Keyword(s):  
Pressure Distribution ◽  
Volume Fraction ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Muscle Fibres ◽  
Pressure Measurements ◽  
Muscle Belly ◽  
Longitudinal Plane ◽  
Order Of Magnitude ◽  
Volume Problem

This paper presents a planar architectural model for an activated skeletal muscle, with mechanical equilibrium throughout the muscle belly. The model can predict the shape of the muscle fibres and tendinous sheets as well as the internal pressure distribution in the central longitudinal plane (perpendicular to the tendinous sheets) of uni- and bipennate muscle bellies. Mechanically stable solutions for muscle architectures were calculated by equating the pressure developed by curved muscle fibres with the pressure under a curved tendinous sheet. The pressure distribution under a tendinous sheet is determined by its tension, its curvature and the tensile stress of the attached muscle fibres. Dissections showed a good resemblance of the architecture of embalmed muscles with those from our simulations. Calculated maximum pressures are in the same order of magnitude as pressure measurements from the literature. Our model predicts that intramuscular blood flow can be blocked during sustained contraction, as several experimental studies have indeed demonstrated. The volume fractions of muscle fibres and interfibre space in the muscle belly were also calculated. The planar models predict a too low volume fraction for the muscle fibres (about 45% for the bipennate models with a straight central aponeurosis, and about 60% for the simulated unipennate muscle). It is discussed how, in a real muscle, this volume problem can be solved by a special three-dimensional arrangement of muscle fibres in combination with varying widths of the tendinous sheets.

A Fast Mask Projection Stereolithography Process for Fabricating Digital Models in Minutes

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Yayue Pan ◽  
Chi Zhou ◽  
Yong Chen
Keyword(s):  
High Speed ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Thin Layers ◽  
Digital Models ◽  
Projection System ◽  
Order Of Magnitude ◽  
Projection Stereolithography ◽  
Direct Digital Manufacturing ◽  
3D Digital Models

The purpose of this paper is to present a direct digital manufacturing (DDM) process that is an order of magnitude faster than other DDM processes that are currently available. The developed process is based on a mask-image-projection-based stereolithography (MIP-SL) process, in which a digital micromirror device (DMD) controls projection light to selectively cure liquid photopolymer resin. In order to achieve high-speed fabrication, we investigate the bottom-up projection system in the MIP-SL process. A two-way linear motion approach has been developed for the quick spreading of liquid resin into uniform thin layers. The system design and related settings for achieving a fabrication speed of a few seconds per layer are presented. Additionally, the hardware, software, and material setups for fabricating three-dimensional (3D) digital models are presented. Experimental studies using the developed testbed have been performed to verify the effectiveness and efficiency of the presented fast MIP-SL process. The test results illustrate that the newly developed process can build a moderately sized part within minutes instead of hours that are typically required.

Computational Model of the Lower Leg and Foot/Ankle Complex: Application to Arch Stability

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Joseph M. Iaquinto ◽  
Jennifer S. Wayne
Keyword(s):  
Soft Tissue ◽  
Computational Model ◽  
Weight Bearing ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Lower Leg ◽  
Physical Parameters ◽  
Spring Ligament ◽  
Ankle Complex

The aim of this work was the design and evaluation of a computational model to predict the functional behavior of the lower leg and foot/ankle complex whereby joint behavior was dictated by three-dimensional articular contact, ligamentous constraints, muscle loading, and external perturbation. Three-dimensional bony anatomy was generated from stacked CT images after which ligament mimicking elements were attached and muscle/body loading added to recreate the experimental conditions of selected cadaveric studies. Comparisons of model predictions to results from two different experimental studies were performed for the function of the medial arch in weight bearing stance and the contributions of soft tissue structures to arch stability. Sensitivity simulations evaluated selected in situ strain and stiffness values for ligament tissue. The greatest contributor to arch stability was the plantar fascia, which provided 79.5% of the resistance to arch collapse, followed by the plantar ligaments (12.5%), and finally the spring ligament (8.0%). Strains measured after plantar fasciotomy increased in the remaining plantar ligament by ∼300% and spring ligament by ∼200%. Sensitivity tests varying both in situ strain and stiffness across reported standard deviations showed that functional trends remained the same and true to experimental data, although absolute magnitudes changed. While not measured experimentally, the model also predicted that load can increase dramatically in the remaining plantar tissues when one of such tissues is removed. Overall, computational predictions of stability and soft tissue load sharing compared well with experimental findings. The strength of this simulation approach lies in its capacity to predict biomechanical behavior of modeled structures and to capture physical parameters of interest not measurable in experimental simulations or in vivo.

Rapid Manufacturing in Minutes: The Development of a Mask Projection Stereolithography Process for High-Speed Fabrication

2012 ◽  
Author(s):  
Yayue Pan ◽  
Chi Zhou ◽  
Yong Chen
Keyword(s):  
High Speed ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Film Coating ◽  
Thin Layers ◽  
Projection System ◽  
Order Of Magnitude ◽  
Cross Links ◽  
Projection Stereolithography ◽  
Direct Digital Manufacturing

The purpose of this paper is to present a direct digital manufacturing (DDM) process that is an order of magnitude faster than other DDM processes currently available. The developed process is based on a mask-image-projection-based Stereolithography process (MIP-SL), during which a Digital Micromirror Device (DMD) controlled projection light cures and cross-links liquid photopolymer resin. In order to achieve high-speed fabrication, we investigated the bottom-up projection system in the MIP-SL process. A set of techniques including film coating and the combination of two-way linear motions have been developed for the quick spreading of liquid resin into uniform thin layers. The process parameters and related settings to achieve the fabrication speed of a few seconds per layer are presented. Additionally, the hardware, software, and material setups developed for fabricating given three-dimensional (3D) digital models are presented. Experimental studies using the developed testbed have been performed to verify the effectiveness and efficiency of the presented fast MIP-SL process. The test results illustrate that the newly developed process can build a moderately sized part within minutes instead of hours that are typically required.

Detection, Averaging, and 3D Reconstruction of Biological Specimens on Hypercubes (Transputer-based) Computers

1990 ◽  
Vol 48 (1) ◽  
pp. 454-455
Author(s):  
Jose-Maria Carazo ◽  
I. Benavides ◽  
S. Marco ◽  
J.L. Carrascosa ◽  
E.L. Zapata
Keyword(s):  
3D Reconstruction ◽  
3D Structure ◽  
Three Dimensional ◽  
Software Tools ◽  
Mapping Method ◽  
Computer Architectures ◽  
Parallel Computer ◽  
Reconstruction Process ◽  
Computing Power ◽  
Order Of Magnitude

Obtaining the three-dimensional (3D) structure of negatively stained biological specimens at a resolution of, typically, 2 - 4 nm is becoming a relatively common practice in an increasing number of laboratories. A combination of new conceptual approaches, new software tools, and faster computers have made this situation possible. However, all these 3D reconstruction processes are quite computer intensive, and the middle term future is full of suggestions entailing an even greater need of computing power. Up to now all published 3D reconstructions in this field have been performed on conventional (sequential) computers, but it is a fact that new parallel computer architectures represent the potential of order-of-magnitude increases in computing power and should, therefore, be considered for their possible application in the most computing intensive tasks.We have studied both shared-memory-based computer architectures, like the BBN Butterfly, and local-memory-based architectures, mainly hypercubes implemented on transputers, where we have used the algorithmic mapping method proposed by Zapata el at. In this work we have developed the basic software tools needed to obtain a 3D reconstruction from non-crystalline specimens (“single particles”) using the so-called Random Conical Tilt Series Method. We start from a pair of images presenting the same field, first tilted (by ≃55°) and then untilted. It is then assumed that we can supply the system with the image of the particle we are looking for (ideally, a 2D average from a previous study) and with a matrix describing the geometrical relationships between the tilted and untilted fields (this step is now accomplished by interactively marking a few pairs of corresponding features in the two fields). From here on the 3D reconstruction process may be run automatically.

Scanning-tunneling spectroscopy on conjugated polymer films

2003 ◽  
Vol 771 ◽  
Author(s):  
M. Kemerink ◽  
S.F. Alvarado ◽  
P.M. Koenraad ◽  
R.A.J. Janssen ◽  
H.W.M. Salemink ◽  
...  
Keyword(s):  
Polymer Films ◽  
Conjugated Polymer ◽  
Three Dimensional ◽  
Field Enhancement ◽  
Direct Consequence ◽  
Scanning Tunneling Spectroscopy ◽  
Tunneling Spectroscopy ◽  
Band Alignment ◽  
Scanning Tunneling ◽  
Order Of Magnitude

AbstractScanning-tunneling spectroscopy experiments have been performed on conjugated polymer films and have been compared to a three-dimensional numerical model for charge injection and transport. It is found that field enhancement near the tip apex leads to significant changes in the injected current, which can amount to more than an order of magnitude, and can even change the polarity of the dominant charge carrier. As a direct consequence, the single-particle band gap and band alignment of the organic material can be directly obtained from tip height-voltage (z-V) curves, provided that the tip has a sufficiently sharp apex.

Diagnostics of metal samples using the results of experimental and theoretical study of positively charged microparticles formed upon sample destruction

2018 ◽  
Vol 84 (10) ◽  
pp. 23-28
Author(s):  
D. A. Golentsov ◽  
A. G. Gulin ◽  
Vladimir A. Likhter ◽  
K. E. Ulybyshev
Keyword(s):  
Experimental Data ◽  
Early Stage ◽  
Experimental Studies ◽  
Material Model ◽  
Total Charge ◽  
Cross Sectional ◽  
Practical Applications ◽  
Mechanical And Electrical Properties ◽  
Order Of Magnitude ◽  
Using Data

Destruction of bodies is accompanied by formation of both large and microscopic fragments. Numerous experiments on the rupture of different samples show that those fragments carry a positive electric charge. his phenomenon is of interest from the viewpoint of its potential application to contactless diagnostics of the early stage of destruction of the elements in various technical devices. However, the lack of understanding the nature of this phenomenon restricts the possibility of its practical applications. Experimental studies were carried out using an apparatus that allowed direct measurements of the total charge of the microparticles formed upon sample rupture and determination of their size and quantity. The results of rupture tests of duralumin and electrical steel showed that the size of microparticles is several tens of microns, the particle charge per particle is on the order of 10–14 C, and their amount can be estimated as the ratio of the cross-sectional area of the sample at the point of discontinuity to the square of the microparticle size. A model of charge formation on the microparticles is developed proceeding from the experimental data and current concept of the electron gas in metals. The model makes it possible to determine the charge of the microparticle using data on the particle size and mechanical and electrical properties of the material. Model estimates of the total charge of particles show order-of-magnitude agreement with the experimental data.

scholarly journals Origin and Application of the Twinned Calcite Strain Gauge

Geosciences ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 296
Author(s):  
Richard H. Groshong
Keyword(s):  
Stress Analysis ◽  
Strain Gauge ◽  
Strain Tensor ◽  
Three Dimensional ◽  
Constant Strain Rate ◽  
Axis Orientation ◽  
Order Of Magnitude ◽  
Rate Experiment ◽  
Strain Axis ◽  
Expected Values

This paper is a personal account of the origin and development of the twinned-calcite strain gauge, its experimental verification, and its relationship to stress analysis. The method allows the calculation of the three-dimensional deviatoric strain tensor based on five or more twin sets. A minimum of about 25 twin sets should provide a reasonably accurate result for the magnitude and orientation of the strain tensor. The opposite-signed strain axis orientation is the most accurately located. Where one strain axis is appreciably different from the other two, that axis is generally within about 10° of the correct value. Experiments confirm a magnitude accuracy of 1% strain over the range of 1–12% axial shortening and that samples with more than 40% negative expected values imply multiple or rotational deformations. If two deformations are at a high angle to one another, the strain calculated from the positive and negative expected values separately provides a good estimate of both deformations. Most stress analysis techniques do not provide useful magnitudes, although most provide a good estimate of the principal strain axis directions. Stress analysis based on the number of twin sets per grain provides a better than order-of-magnitude approximation to the differential stress magnitude in a constant strain rate experiment.

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