scholarly journals Performance Optimization of a Condenser in Ocean Thermal Energy Conversion (OTEC) System Based on Constructal Theory and a Multi-Objective Genetic Algorithm

Entropy ◽  
2020 ◽  
Vol 22 (6) ◽  
pp. 641 ◽  
Author(s):  
Zhixiang Wu ◽  
Huijun Feng ◽  
Lingen Chen ◽  
Yanlin Ge
Keyword(s):  
Heat Transfer ◽  
Genetic Algorithm ◽  
Constructal Theory ◽  
Pareto Optimal ◽  
Effective Volume ◽  
Pareto Optimal Set ◽  
Thermal Energy Conversion ◽  
Multi Objective Genetic Algorithm ◽  
Ocean Thermal Energy ◽  
Optimal Set

Constructal optimization of a plate condenser with fixed heat transfer rate and effective volume in ocean thermal energy conversion (OTEC) system is performed based on constructal theory. Optimizations of entropy generation rate ( S ˙ g ) in heat transfer process and total pumping power ( P sum ) due to friction loss are two conflicting objectives for a plate condenser. With the conventional optimization method, the plate condenser is designed by taking a composite function (CF) considering both S ˙ g and P sum as optimization objectives, and employing effective length, width, and effective number of heat transfer plates as design variables. Effects of structural parameters of the plate condenser and weighting coefficient of CF on design results are investigated. With a multi-objective genetic algorithm, the plate condenser is designed by simultaneously optimizing S ˙ g and P sum , and the Pareto optimal set is obtained. The results demonstrate that CFs after primary and twice-constructal optimizations are respectively reduced by 7.8% and 9.9% compared with the initial CF, and the effective volume of the plate condenser has a positive impact on the twice minimum CF. Furthermore, the Pareto optimal set can provide better selections for performance optimizations of plate condensers.

Geometric Size Optimization of Annular Step Fin Using Multi-Objective Genetic Algorithm

2017 ◽  
Vol 9 (2) ◽  
Author(s):  
Abhijit Deka ◽  
Dilip Datta
Keyword(s):  
Heat Transfer ◽  
Genetic Algorithm ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Pareto Optimal ◽  
Objective Functions ◽  
Cross Sectional ◽  
Multi Objective ◽  
Multi Objective Genetic Algorithm ◽  
Design Variables

Although an annular stepped fin can produce better cooling effect in comparison to an annular disk fin, it is yet to be studied in detail. In the present work, one-dimensional heat transfer in a two-stepped rectangular cross-sectional annular fin with constant base temperature and variable thermal conductivity is modeled as a multi-objective optimization problem. Taking cross-sectional half-thicknesses and outer radii of the two fin steps as design variables, an attempt is made to obtain the efficient fin geometry primarily by simultaneously maximizing the heat transfer rate and minimizing the fin volume. For further assessment of the fin performance, three more objective functions are studied, which are minimization of the fin surface area and maximization of the fin efficiency and effectiveness. Evaluating the heat transfer rate through the hybrid spline difference method, the well-known multi-objective genetic algorithm, namely, nondominated sorting genetic algorithm II (NSGA-II), is employed for approximating the Pareto-optimal front containing a set of tradeoff solutions in terms of different combinations of the considered five objective functions. The Pareto-optimal sensitivity is also analyzed for studying the influences of the design variables on the objective functions. As an outcome, it can be concluded that the proposed procedure would give an open choice to designers to lead to a practical stepped fin configuration.

scholarly journals Multi-Objective Constructal Optimization for Marine Condensers

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5545
Author(s):  
Huijun Feng ◽  
Wei Tang ◽  
Lingen Chen ◽  
Junchao Shi ◽  
Zhixiang Wu
Keyword(s):  
Heat Transfer ◽  
Entropy Generation Rate ◽  
Working Fluid ◽  
Pareto Optimal ◽  
Pumping Power ◽  
Multi Objective ◽  
Pareto Optimal Set ◽  
Deviation Index ◽  
Optimal Set ◽  
Single Objective

A marine condenser with exhausted steam as the working fluid is researched in this paper. Constructal designs of the condenser are numerically conducted based on single and multi-objective optimizations, respectively. In the single objective optimization, there is an optimal dimensionless tube diameter leading to the minimum total pumping power required by the condenser. After constructal optimization, the total pumping power is decreased by 42.3%. In addition, with the increase in mass flow rate of the steam and heat transfer area and the decrease in total heat transfer rate, the minimum total pumping power required by the condenser decreases. In the multi-objective optimization, the Pareto optimal set of the entropy generation rate and total pumping power is gained. The optimal results gained by three decision methods in the Pareto optimal set and single objective optimizations are compared by the deviation index. The optimal construct gained by the TOPSIS decision method corresponding to the smallest deviation index is recommended in the optimal design of the condenser. These research ideas can also be used to design other heat transfer devices.

Biofouling Monitors for Noncylindrical OTEC Heat Exchanger Tubes

1982 ◽  
Vol 104 (3) ◽  
pp. 257-261
Author(s):  
T. M. Kuzay ◽  
C. B. Panchal ◽  
A. P. Gavin
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Steel Tube ◽  
Stainless Steel Tube ◽  
Thermal Energy Conversion ◽  
Shell And Tube ◽  
Ocean Thermal Energy ◽  
Analytical Approaches

Heat-transfer monitors (HTMs) have been used since 1976 to measure the reduction in the seawater heat-transfer coefficient due to buildup of biofouling and corrosion products inside circular tubes of shell-and-tube heat exchangers being developed for ocean thermal energy conversion (OTEC) plants. For OTEC heat exchangers (HXs) with other tube geometries, special, modified HTMs, which we call STMs, are being sought. The analytical approaches and calibration results to date are summarized for STMs of two types: (i) an STM simulating a rectangular seawater passage in a compact, aluminum, plate-fin HX, and (ii) an STM for a helical stainless-steel tube. The development of type 1 has been successful. A software change is needed for type 2.

Analytical Derivation of the Pareto-Optimal Set with Application to Structural Design

2020 ◽  
pp. 43-66
Author(s):  
Federico Maria Ballo ◽  
Massimiliano Gobbi ◽  
Giampiero Mastinu ◽  
Giorgio Previati
Keyword(s):  
Structural Design ◽  
Pareto Optimal ◽  
Analytical Derivation ◽  
Pareto Optimal Set ◽  
Optimal Set

Optimal Approximation of Real Values Using Rational Numbers With Application to the Kinematic Design of Gearboxes

1993 ◽  
Author(s):  
Leonard P. Pomrehn ◽  
Panos Y. Papalambros
Keyword(s):  
Design Problem ◽  
Rational Numbers ◽  
Optimal Approximation ◽  
Pareto Optimal ◽  
Individual Stage ◽  
Gear Teeth ◽  
Kinematic Design ◽  
Pareto Optimal Set ◽  
Reducing Gear ◽  
Optimal Set

Abstract This article proposes a method for optimally approximating real values with rational numbers. Such requirements arise in the design of various types of gear sets, where integer numbers of gear teeth force individual stage ratios to assume rational values. The kinematic design of an 18-speed gearbox, taken from the literature, is analyzed and solved using the proposed method. The method, called sequential exhaustion, sequentially considers each stage of the gearbox design, exhaustively examining each stage. Examination of 94 solutions leads to a pareto-optimal set containing 11 solutions. Further, although the layout of the gearbox is predefined for the kinematic design problem, certain solutions of the problem exhibit “non-reducing” gear pairs, revealing previously unforeseen changes in the gearbox layout.

Sign in / Sign up

Export Citation Format

Share Document