Showing papers on "Constructal law published in 2018"

Constructal Optimizations for Heat and Mass Transfers Based on the Entransy Dissipation Extremum Principle, Performed at the Naval University of Engineering: A Review.

Abstract: Combining entransy theory with constructal theory, this mini-review paper summarizes the constructal optimization work of heat conduction, convective heat transfer, and mass transfer problems during the authors' working time in the Naval University of Engineering. The entransy dissipation extremum principle (EDEP) is applied in constructal optimizations, and this paper is divided into three parts. The first part is constructal entransy dissipation rate minimizations of heat conduction and finned cooling problems. It includes constructal optimization for a "volume-to-point" heat-conduction assembly with a tapered element, constructal optimizations for "disc-to-point" heat-conduction assemblies with the premise of an optimized last-order construct and without this premise, and constructal optimizations for four kinds of fin assemblies: T-, Y-, umbrella-, and tree-shaped fins. The second part is constructal entransy dissipation rate minimizations of cooling channel and steam generator problems. It includes constructal optimizations for heat generating volumes with tree-shaped and parallel channels, constructal optimization for heat generating volume cooled by forced convection, and constructal optimization for a steam generator. The third part is constructal entransy dissipation rate minimizations of mass transfer problems. It includes constructal optimizations for "volume-to-point" rectangular assemblies with constant and tapered channels, and constructal optimizations for "disc-to-point" assemblies with the premise of an optimized last-order construct and without this premise. The results of the three parts show that the mean heat transfer temperature differences of the heat conduction assemblies are not always decreased when their internal complexity increases. The average heat transfer rate of the steam generator obtained by entransy dissipation rate maximization is increased by 58.7% compared with that obtained by heat transfer rate maximization. Compared with the rectangular mass transfer assembly with a constant high permeability pathway (HPP), the maximum pressure drops of the element and first-order assembly with tapered HPPs are decreased by 6% and 11%, respectively. The global transfer performances of the transfer bodies are improved after optimizations, and new design guidelines derived by EDEP, which are different from the conventional optimization objectives, are provided.

Constructal law and ion transfer in normal and cancer cells

Abstract: All the living systems waste heat into environment. It is no more than the result of their internal irreversibility. The Constructal law analysis of the irreversibility related to this wasted heat represents a new useful approach to the study of the cells behaviour. This approach allows us to consider the living systems as black boxes and analyze only the inflows and outflows of energy and mass, and their changes in relation to any environmental modification. The consequence is the analysis of the effect of the ions transport through the membrane, and the related cell-environment pH changes, with consideration on the Krebs or Warburg cycle, used for energy conversion, by the normal and cancer cells respectively. Consequently, the entropy generation related to the pH changes can be obtained, and related to mitosis/apoptosis ratio, fundamental to evaluate the probability of evolution of cancer.

Constructal Design Applied to the Geometric Evaluation of an Oscillating Water Column Wave Energy Converter Considering Different Real Scale Wave Periods

Abstract: The present work presents numerical study of the influence of geometry on the performance of an oscillating water column (OWC) wave energy converter by means of a constructal design. The main purpose is to maximize the root mean square hydrodynamic power of device, (Phyd)RMS, subject to several real scale waves with different periods. The problem has two constraints: hydropneumatic chamber volume (V HC ) and total OWC volume (V T ), and two degrees of freedom: H1/L (ratio of height to length of the hydropneumatic chamber) and H3 (OWC submergence). For the numerical solution it was used a computational fluid dynamic (CFD) code, based on the finite volume method (FVM). The multiphasic volume of fluid (VOF) model is applied to tackle with the water–air interaction. The results led to important theoretical recommendations about the design of OWC device. For instance, the best shape for OWC chamber, which maximizes the (Phyd)RMS, was achieved when the ratio (H1/L) was four times higher than the ratio of height to length of incident wave (H/λ), (H1/L) o = 4(H/λ). Moreover, the optimal submergence (H3) was achieved as a function of wave height (H) and water depth (h), more precisely given by the following relation: h − (3H/4) ≤ (H3) o ≤ h.

Constructal heat conduction optimization: Progresses with entransy dissipation rate minimization

Abstract: Combining entransy theory with constructal theory in heat transfer optimization, this review summarizes constructal entransy dissipation optimizations of ‘volume-point’ heat conduction problem, optimal design of heat exchangers and multidisciplinary and multi-objective optimization of electromagnets performed in the Naval University of Engineering. It consists of the following four parts: optimization of volume-point heat conduction; optimal design of disc cooling problem; optimal design of cross-profile of a double pipe heat exchanger constituted of porous medium material; and multidisciplinary and multi-objective optimization for electromagnet. Some valuable results for designer are achieved and stated as follows: (1) Whether the heat transfer density is linear increasing is the key for the discrepancies between the two geometries with the objectives of maximum temperature difference minimization (MTDM) and entransy dissipation rate minimization (EDRM). (2) Based on discrete variable cross-profile conductive path, a new constructal basic unit which is more suitable with heat density distribution is established. (3) An index which can reflect magnetic intensity and heat transfer ability at the same time is proposed and multidisciplinary and multi-objective optimizations of electromagnet are realized. (4) A self-similar constructal optimization method which can improve the heat transfer ability steadily through assembling is proposed.

Design approach for additive manufacturing employing Constructal Theory for point-to-circle flows

Abstract: Design is crucial for additive manufacturing (AM). Not only does it affect manufacturability and cost but more importantly does it determine the functional performance of a part. Design for additive manufacturing (DFAM) methods consider these aspects and aim to leverage the available design freedom in order to generate functionally optimized parts. The following research work presents a method that is based on design principles from the so-called Constructal Theory. Two design principles are selected form this discipline, which considers design a field of science. The first principle outlines how a fluid flow can be distributed efficiently using a tree-shaped structure. The second principle emphasizes to first create the flow structure and then fit the surrounding solid body around it following the flow of mechanical stress. To demonstrate the approach, a case study of a gear wheel design is presented, which integrates cooling lubricant channels and focuses on minimal part mass. Based on analytical relations, a design concept is generated that provides a mass reduction of 25% and a fluid channel structure with minimal required pumping power. The resulting design serves as starting point for a more detailed simulation-based design optimization.

Constructal Design of a Rectangular Fin in a Mixed Convective Confined Environment

Abstract: Extended surfaces or fins offer an efficient solution in many engineering situations that demand a higher heat transfer, including cooling gas-turbine components and electronic chips via internal convective flows. However, fins require a higher active surface area for higher heat transfer, which may not be always feasible in a confined environment. A feasible solution to enhance heat transfer from fins can be the use of nanofluids, which are the combination of a fluid base and nanoparticles. The main purpose of this study is, therefore, to optimize a rectangular fin intruded into the mixed convective confined space filled with a nanofluid and by means of constructal design. Here, a two-dimensional macroscopic numerical model has been developed for Al2O3–water nanofluid to investigate the heat transfer and fluid flow inside a square confined-space with an intruded rectangular fin and to optimize the fin geometry for maximizing the heat transfer using the constructal design method. The flow fields, temperature fields, heat transfer rates, and the transition from forced to mixed convection are examined for different values of Rayleigh and Reynolds numbers for various fin geometries in order to maximize the heat transfer from the fin to the surrounding nanofluid flow. The outcome of this study provides important insights into the constructal design method for the confined environment, which would be beneficial in developing novel fin geometries with enhanced and controlled heat-transfer for engineering problems, including cooling gas-turbine components and electronic chips.

Constructal Optimization for Cooling a Non-Uniform Heat Generating Radial-Pattern Disc by Conduction.

Abstract: A heat conduction model in a radial-pattern disc by considering non-uniform heat generation (NUHG) is established in this paper. A series of high conductivity channels (HCCs) are attached on the rim of the disc and extended to its center. Constructal optimizations of the discs with constant and variable cross-sectional HCCs are carried out, respectively, and their maximum temperature differences (MTDs) are minimized based on analytical method and finite element method. Besides, the influences of the NUHG coefficient, HCC number and width coefficient on the optimal results are studied. The results indicate that the deviation of the optimal constructs obtained from the analytical method and finite element method are comparatively slight. When the NUHG coefficient is equal to 10, the minimum MTD of the disc with 25 constant cross-sectional HCCs is specifically reduced by 48.8% compared to that with 10 HCCs. As a result, the heat conduction performance (HCP) of the disc can be efficiently improved by properly increasing the number of HCCs. The minimum MTD of the disc with variable cross-sectional HCC is decreased by 15.0% when the width coefficient is changed from 1 to 4. Therefore, the geometry of variable cross-sectional HCC can be applied in the constructal design of the disc to a better heat transfer performance. The constructal results obtained by investigating the non-uniform heat generating case in this paper can contribute to the design of practical electronic device to a better heat transfer performance.

Two-dimensional geometric optimization of an oscillating water column converter in laboratory scale

Abstract: The present paper presents a two-dimensional numerical study about the geometric optimization of an ocean Wave Energy Converter (WEC) into electrical energy that has as operational principal the Oscillating Water Column (OWC). To do so, the Constructal Design fundamentals were employed to vary the degree of freedom H1/L (ratio between height and length of the OWC chamber), while the other degree of freedom H2/l (ration between height and length of chimney) was kept constant. The OWC chamber area (φ1) and the total OWC area (φ2) are also kept fixed, being the problem constraints. In this study was adopted a regular wave with laboratory scale dimensions. The main goal was to optimize the device's geometry aiming to maximize the absorbed power when it is subjected to a defined wave climate. For the numerical solution it was used the Computational Fluid Dynamic (CFD) commercial code FLUENT ® , which is based on the Finite Volume Method (FVM). The multiphasic Volume of Fluid (VOF) model was applied to treat the water-air interaction. The computational domain was represented by an OWC device coupled into a wave tank. Thereby, it was possible to analyze the WEC subjected to regular wave incidence. An optimal geometry was obtained for (H1/L)o= 0.84, being this one approximately ten times more efficient then the worst case (H1/L = 0.14), showing the applicability of Constructal Design in this kind of engineering problem.

Molten steel yield optimization of a converter based on constructal theory

Abstract: Constructal theory is introduced into the molten steel yield maximization of a converter in this paper. For the specific total cost of materials, generalized constructal optimization of a converter steel-making process is performed. The optimal cost distribution of materials is obtained, and is also called as “generalized optimal construct”. The effects of the hot metal composition contents, hot metal temperature, slag basicity and ratio of the waste steel price to the sinter ore price on the optimization results are analyzed. The results show that the molten steel yield after optimization is increased by 5.48% compared with that before optimization when sinter ore and waste steel are taken as the coolants, and the molten steel yield is increased by 6.84% when only the sinter ore is taken as the coolant. It means that taking sinter ore as coolant can improve the economic performance of the converter steelmaking process. Decreasing the contents of the silicon, phosphorus and manganese in the hot metal can increase the molten steel yield. The change of slag basicity affects the molten steel yield a little.

Can constructal law and exergy analysis produce a robust design method that couples with industry 4.0 paradigms? The case of a container house

Abstract: Received: 26 May 2018 Accepted: 19 November 2018 Constructal law deals with evolution and generation of new configurations of a physical system according to first and the second law of thermodynamics. Constructal law based design allows understanding the basic principles of the evolution of design in nature and to evolve a system through the maximization of its efficiency. On the other side, Digital Twin is a foundational paradigm of Industry 4.0. Digital Twin is the technological framework that allows an effective lifecycle analysis of a system and an effective comparison of different configurations. It allows determining the digital model of a physical system and replicating its evolution. This paper investigates how they can be complementary instruments of engineering and design process inside a knowledge based framework that opens the way through a knowledge-based, holistic and evolutional perspective in engineering. This paper aims to verify if an extended and evolved digital twin model that conforms with a multidisciplinary application of constructal law can be realized through the design of an optimized low-cost container house for social housing. The results demonstrate not only the efficiency and the results of the proposed system and that the results allow an effective improvement of the system performances and that this improvement is realized through an effective design which can be realized as it is with a finite precision, which is the one that is allowed by the real industrial components.

Constructal design applied to the study of cavities into a solid conducting wall

Abstract: This paper relies on the Constructal Design to optimize the geometry of a cavity that penetrates into a solid conducting wall. The objective is to minimize the global thermal resistance between the solid and the cavity. There is uniform heat generation on the solid wall. We studied three shapes of the cavity: rectangular, triangular, and elliptical. The total volume and the cavity volume are fixed with variable aspect ratios. The cavity shape is optimal when it penetrates the conducting wall completely. The rectangular cavity performs better than the elliptical and triangular ones. On the other side, the elliptical cavity has better performance than the triangular one. We also optimized a first construct, i.e., a cavity shaped as T. The performance of the T-shaped cavity is superior to that of the rectangular cavity optimized in the first part of the paper.

A Constructal Law optimization of a boiler inspired by Life Cycle thinking

Abstract: The aim of the paper is to explore how design optimization contributes to a technology's ecological evolution. The article develops this concept through an application of Constructal Law, used to account for the “evolution” of technologies design (configuration, shape, structure, pattern, rhythm), and Life Cycle Assessment (LCA), used for quantifying the environmental impacts of the design choices. The combination of both methods assesses how technology evolution affects the environment during its life, extending the concept of evolution of design. The study is applied to a case study of a real biomass boiler. The study analyses basic case and a series of alternative scenarios optimized with Constructal Law, guaranteeing the same thermal energy production. The results are analyzed graphically and analytically with an “Overall Performance Coefficient methodology”, that investigates trade-offs to identify the best configuration. In addition, the use of LCA allows evaluating energy and environmental performances of different design alternatives, with the best option able to reduce the global energy required of 0.33% and the normalized impacts of 4%. The methodology is proposed to support decision-making during the optimization process.