The combined impacts of leg geometry configuration and multi-staging on the exergetic performance of thermoelectric modules in a solar thermoelectric generator

2021 ◽  
pp. 1-23
Author(s):  
Chika Maduabuchi ◽  
Sarveshwar Singh ◽  
Chigbogu G Ozoegwu ◽  
Howard Njoku ◽  
Mkpamdi Eke
Keyword(s):  
Load Resistance ◽  
Base Case ◽  
Two Stage ◽  
Hybrid Device ◽  
Multi Stage ◽  
Geometry Configuration ◽  
Solar Thermoelectric Generator ◽  
Concentrated Solar Radiation ◽  
Power Densities ◽  
Modelling And Optimization

Abstract The performance of thermoelectric generators (TEGs) can be improved either by the adoption of multi-stage or tapered leg configuration. So far, a hybrid device that simultaneously uses both multi-staging and tapered leg geometry to improve its performance has not been conceived. Thus, we present a thermodynamic modelling and optimization of a two-stage TEG with tapered leg geometries using ANSYS 2020 R2 software. The optimized parameters include the leg height, area, concentrated solar radiation and external load resistance. Firstly, the X-leg TEG only improves the performance of the trapezoidal leg TEG below a leg height of 3 mm. Beyond 3 mm, the performance of both TEGs become very similar. Long thermoelectric legs provide higher efficiencies, while short legs generate maximum power densities. To obtain maximum efficiencies, the initial leg height of the thermoelectric legs, 1.62 mm, is increased by 517.28%, while the initial leg area, 1.96 mm2, is decreased by 64.29%. Also, the proposed two-stage TEG with tapered legs (trapezoidal and X-legs) improves the exergetic efficiency of the base case, single-stage rectangular leg TEG, by 16.7%. Furthermore, the use of tapered leg TEGs; in single and multi-stage arrangements, reduces the exergy conversion index of conventional rectangular leg TEGs by 1.89% and 0.98%, respectively. Finally, the use of tapered legs and multi-stage configurations increases the thermodynamic irreversibilities of conventional rectangular leg TEGs, thus, reducing their thermodynamic stability.

scholarly journals Generalized optimizations of two-stage forging of micro/meso copper fastener

2018 ◽  
Vol 185 ◽  
pp. 00002
Author(s):  
Shih-Hsien Lin ◽  
Un-Chin Chai ◽  
Gow-Yi Tzou ◽  
Dyi-Cheng Chen
Keyword(s):  
Simulation Analysis ◽  
Effective Strain ◽  
Cold Forging ◽  
Two Stage ◽  
Forming Simulation ◽  
Multi Stage ◽  
Element Simulation ◽  
Die Stress ◽  
Stress Optimization ◽  
Forging Force

Three are generalized simulation optimizations considering the forging force, the die stress, and the dual-goals in two-stage forging of micro/meso copper fastener. Constant shear friction between the dies and workpiece is assumed to perform multi-stage cold forging forming simulation analysis, and the Taguchi method with the finite element simulation has been used for mold-and-dies parameters design simulation optimizations considering the forging force, die stress, and dual-goals. The die stress optimization is used to explore the effects on effective stress, effective strain, velocity field, die stress, forging force, and shape of product. The influence rank to forging process of micro/meso copper fastener for three optimizations can be determined, and the optimal parameters assembly consider die stress can be obtained in this study. It is noted that the punch design innovation can reduce the forging force and die stress.

Integrated Systems for Cogeneration and Absorption Chilling: Comparison for Varying Chiller COPs

1999 ◽  
Author(s):  
R. Tang ◽  
M. A. Rosen
Keyword(s):  
Steam Turbine ◽  
Integrated System ◽  
Coefficient Of Performance ◽  
Integrated Systems ◽  
Base Case ◽  
Cooling Load ◽  
Absorption Chillers ◽  
Multi Stage ◽  
Wide Range ◽  
Thermodynamic Effects

Abstract The thermodynamic effects are demonstrated of integrating steam turbine-based cogeneration systems with absorption chillers. A wide range of realistic extraction steam pressures and coefficient of performance (COP) values of absorption chillers are considered. A simple model of a steam turbine-based cogeneration plant is used for the evaluation of the integrated system. The integrated systems are evaluated based on the ratio of fuel consumption between a base case (one-stage absorption chiller with a COP value of 0.6) and several alternative cases (multi-stage absorption chillers with COP values ranging from 0.6 to 1.5). Two categories of scenarios are considered: (i) cases where the cooling load is fixed; and (ii) cases where the cooling load is fixed and the electrical output for the integrated system is set equal to that for the base case.

Optimal Longevity Risk Management in the Retirement Stage of the Life Cycle

2018 ◽  
Keyword(s):  
Life Cycle ◽  
Life Expectancy ◽  
Asset Allocation ◽  
Wealth Distribution ◽  
Critical Role ◽  
Relative Price ◽  
Base Case ◽  
Longevity Risk ◽  
Allocation Policy ◽  
Multi Stage

The uncertainty in life expectancy plays a critical role in individual financial planning. Its impact is magnified during the retirement years (the wealth distribution stage of the life cycle), as new sources of income typically are not available to retired persons. Utilizing a multi-stage stochastic program, the authors model and solve the optimal asset allocation problem of a retired couple with uncertain life expectancy in the presence of a term life insurance policy. In the base case, they find optimal policies assuming no longevity risk (i.e., lifetime scenarios are uncertain although life expectancy is fixed on the retirement date). Next, they introduce longevity risk in the scenario generation stage through either a shift in the expected lifetimes or an unexpected cut in periodic retirement income. The authors find that the optimal asset allocation policy depends on the presence and the type of these risks, as well as the relative price of insurance and the size of any cut in pension benefits.

Dealing with Inaccurate Measures of Size in Two-Stage Probability Proportional to Size Sample Designs: Applications in African Household Surveys

2020 ◽  
Author(s):  
Graham Kalton ◽  
Ismael Flores Cervantes ◽  
Carlos Arieira ◽  
Mike Kwanisai ◽  
Elizabeth Radin ◽  
...  
Keyword(s):  
Final Stage ◽  
Population Based ◽  
Equal Probability ◽  
Household Surveys ◽  
Sample Design ◽  
African Countries ◽  
Two Stage ◽  
Fixed Sample ◽  
Multi Stage ◽  
Weighting Adjustments

Abstract The units at the early stages of multi-stage area samples are generally sampled with probabilities proportional to their estimated sizes (PPES). With such a design, an overall equal probability (EP) sample design would yield a constant number of final stage units from each final stage cluster if the measures of size used in the PPES selection at each sampling stage were directly proportional to the number of final stage units. However, there are often sizable relative differences between the measures of size used in the PPES selections and the number of final stage units. Two common approaches for dealing with these differences are: (1) to retain a self-weighting sample design, allowing the sample sizes to vary across the sampled primary sampling units (PSUs) and (2) to retain the fixed sample size in each PSU and to compensate for the unequal selection probabilities by weighting adjustments in the analyses. This article examines these alternative designs in the context of two-stage sampling in which PSUs are sampled with PPES at the first stage, and an equal probability sample of final stage units is selected from each sampled PSU at the second stage. Two-stage sample designs of this type are used for household surveys in many countries. The discussion is illustrated with data from the Population-based HIV Impact Assessment surveys that were conducted using this design in several African countries.

scholarly journals A Review on Anaerobic Co-Digestion with a Focus on the Microbial Populations and the Effect of Multi-Stage Digester Configuration

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1106 ◽  
Author(s):  
Anahita Rabii ◽  
Saad Aldin ◽  
Yaser Dahman ◽  
Elsayed Elbeshbishy
Keyword(s):  
Anaerobic Digestion ◽  
Microbial Population ◽  
System Stability ◽  
Microbial Consortia ◽  
Microbial Populations ◽  
Stage Versus ◽  
Two Stage ◽  
Waste Sludge ◽  
Multi Stage ◽  
Mode A

Recent studies have shown that anaerobic co-digestion (AnCoD) is superior to conventional anaerobic digestion (AD). The benefits of enhanced bioenergy production and solids reduction using co-substrates have attracted researchers to study the co-digestion technology and to better understand the effect of multi substrates on digester performance. This review will discuss the results of such studies with the main focus on: (1) generally the advantages of co-digestion over mono-digestion in terms of system stability, bioenergy, and solids reduction; (2) microbial consortia diversity and their synergistic impact on biogas improvement; (3) the effect of digester mode, i.e., multi-stage versus single stage digestion on AnCoD. It is essential to note that the studies reported improvement in the synergy and diverse microbial consortia when using co-digestion technologies, in addition to higher biomethane yield when using two-stage mode. A good example would be the co-digestion of biodiesel waste and glycerin with municipal waste sludge in a two-stage reactor resulting in 100% increase of biogas and 120% increase in the methane content of the produced biogas with microbial population dominated by Methanosaeta and Methanomicrobium.

Genetic Algorithm to Solve Multi-Period, Multi-Product, Bi-Echelon Supply Chain Network Design Problem

2009 ◽  
Vol 2 (4) ◽  
pp. 24-42 ◽  
Author(s):  
R. Dhanalakshmi ◽  
P. Parthiban ◽  
K. Ganesh ◽  
T. Arunkumar
Keyword(s):  
Supply Chain ◽  
Supply Chains ◽  
Raw Materials ◽  
Optimization Techniques ◽  
Network Design Problem ◽  
Production Plant ◽  
Two Stage ◽  
Cost Structures ◽  
Multi Stage ◽  
Product Costs

In many multi-stage manufacturing supply chains, transportation related costs are a significant portion of final product costs. It is often crucial for successful decision making approaches in multi-stage manufacturing supply chains to explicitly account for non-linear transportation costs. In this article, we have explored this problem by considering a Two-Stage Production-Transportation (TSPT). A two-stage supply chain that faces a deterministic stream of external demands for a single product is considered. A finite supply of raw materials, and finite production at stage one has been assumed. Items are manufactured at stage one and transported to stage two, where the storage capacity of the warehouses is limited. Packaging is completed at stage two (that is, value is added to each item, but no new items are created), and the finished goods inventories are stored which is used to meet the final demand of customers. During each period, the optimized production levels in stage one, as well as transportation levels between stage one and stage two and routing structure from the production plant to warehouses and then to customers, must be determined. The authors consider “different cost structures,” for both manufacturing and transportation. This TSPT model with capacity constraint at both stages is optimized using Genetic Algorithms (GA) and the results obtained are compared with the results of other optimization techniques of complete enumeration, LINDO, and CPLEX.

Structure and Propagation of Rotating Stall in a Single- and a Multi-Stage Axial Compressor

1999 ◽  
Author(s):  
H. M. Saxer-Felici ◽  
A. P. Saxer ◽  
F. Ginter ◽  
A. Inderbitzin ◽  
G. Gyarmathy
Keyword(s):  
Numerical Solutions ◽  
Equations Of Motion ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Water Model ◽  
Two Stage ◽  
Additional Information ◽  
Driving Mechanisms ◽  
Multi Stage ◽  
Stall Cells

The structure and propagation of rotating stall cells in a single- and a two-stage subsonic axial compressor is addressed in this paper using computational and experimental analysis. Unsteady solutions of the 2-D inviscid compressible (Euler) equations of motion are presented for one operating point in the fully-developed rotating stall regime for both a single- and a two-stage compressor. The inviscid assumption is verified by comparing the single-stage 2-D in viscid/compressible solution with an equivalent 2-D viscous (Navier-Stokes) result for incompressible flow. The structure of the rotating stall cell is analyzed and compared for the single- and two-stage cases. The numerical solutions are validated against experimental data consisting of flow visualization and unsteady row-by-row static pressure measurements obtained in a four-stage water model of a subsonic compressor. The CFD solutions supply a link between the observed experimental features and provide additional information on the structure of the stall flow. Based on this study. supporting assumptions regarding the driving mechanisms for the propagation of fully-developed rotating stall cells and their structure are postulated. In methodical respect the results suggest that the inviscid model is able to reproduce the essentials of the flow physics associated with the propagation of fully-developed, full-span rotating stall in a subsonic axial compressor.

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