Geometric and Thermodynamic Optimization of a Heat Recovery Steam Generator: A Constructal Design

Pin-fins are considered as one of the best elements for heat transfer enhancement in heat exchangers. In this study, the topology of pin-fins (length, diameter, and shape) is optimized based on the entropy generation minimization (EGM) theory coupled with the constructal law (CL). Such pin-fins are employed in a heat exchanger in a sensible thermal energy storage (TES) system so as to enhance the rate of heat transfer. First, the EGM method is used to obtain the optimal length of pin-fins, and then the CL is applied to get the optimal diameter and shape of pin-fins. Reliable computational fluid dynamics (CFD) simulations of various constructal pin-fin models are performed, and detailed flow and heat transfer characteristics are presented. The results show that by using the proposed system with optimized pin-fin heat exchanger the stored thermal energy can be increased by 10.2%.

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“…Other recent applications of CL were documented in Refs. [21][22][23][24][25] and a newly edited book [26].…”

Section: Introductionmentioning

confidence: 99%

Optimization of Pin-Fins for a Heat Exchanger by Entropy Generation Minimization and Constructal Law

Xie

Song

Asadi

et al. 2015

Journal of Heat Transfer

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“…Kim et al [ 70 , 71 ] maximized the heat transfer rate (HTR) of a steam generator with fixed volumes of a steam generator and heat transfer tubes and obtained the optimal adjacent space and numbers of the riser and downcomer tubes. Norouzi et al [ 72 ] conducted constructal design of a heat recovery steam generator and minimized the entropy generation number of a steam generator by optimizing the tube radii of the economizer, evaporator, and superheater, respectively. Mehrgoo and Amidpour [ 73 ] further optimized entropy generation performance of a dual pressure heat recovery steam generator and found that the total volume of the steam generator had its optimum value and the heat conductance of the evaporator was big.…”

Section: Constructal Optimizations Based On the Entransy Dissipatimentioning

confidence: 99%

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

Chen

Xiao

2018

Entropy

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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.

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“…Advances are published regularly for heat exchangers [4][5][6][7][8][9][10][11][12][13], fuel cells [14], fluid networks [15][16][17][18][19][20], steam generators [21,22], fluid channels [23][24][25][26][27], energy storage [28], transportation [29][30][31][32], power generation [33][34][35][36][37], and management [38].…”

Section: Technology Evolutionmentioning

confidence: 99%

Entrance-length dendritic plate heat exchangers

Bejan

Alalaimi

Sabau

et al. 2017

International Journal of Heat and Mass Transfer

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a b s t r a c tHere we explore the idea that the highest heat transfer rate between two fluids in a given volume is achieved when plate channel lengths are given by the thermal entrance length, i.e., when the thermal boundary layers meet at the exit of each channel. The overall design can be thought of an elemental construct of a dendritic heat exchanger, which consists of two tree-shaped streams arranged in cross flow. Every channel is as long as the thermal entrance length of the developing flow that resides in that channel. The results indicate that the overall design will change with the total volume and total number of channels. We found that the lengths of the surfaces swept in cross flow would have to decrease sizably as number of channels increases, while exhibiting mild decreases as total volume increases. The aspect ratio of each surface swept by fluid in cross flow should be approximately square, independent of total number of channels and volume. We also found that the minimum pumping power decreases sensibly as the total number of channels and the volume increase. The maximized heat transfer rate per unit volume increases sharply as the total volume decreases, in agreement with the natural evolution toward miniaturization in technology.

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Geometric and Thermodynamic Optimization of a Heat Recovery Steam Generator: A Constructal Design

Cited by 13 publications

References 29 publications

Optimization of Pin-Fins for a Heat Exchanger by Entropy Generation Minimization and Constructal Law

Optimization of Pin-Fins for a Heat Exchanger by Entropy Generation Minimization and Constructal Law

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

Entrance-length dendritic plate heat exchangers

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