Constructal-theory tree networks of “constant” thermal resistance

Neagu, Maria; Bejan, Adrian

doi:10.1063/1.370855

Cited by 92 publications

(51 citation statements)

References 8 publications

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“…As shown in Figure 1 [24], the heat is generated uniformly at a rate q′′′(W/m 3 ) and the heat source is uniformly distributed. The heat is first directed to a high-conductivity link (the thermal conductivity of the material is k p , the thermal conductivity of the other material is k 0 , and k p k 0 ) of variable width D 0 (D 0 is free to vary along the x-direction and is denoted as D 0 (x)) and is removed from the system through a path of temperature T min located at x=L 0 and y=0 (M 0 ).…”

Section: Elemental Optimizationmentioning

confidence: 99%

“…From this, we will obtain the mean temperature difference for a given control-volume and the optimal shapes of the element and high-conductivity link. We will then present some interesting conclusions via a comparison with results obtained based on the maximum temperature difference minimization in [24].…”

mentioning

confidence: 95%

“…However, using the minimization of the maximum temperature difference in [24], the optimal construct was found to be H 0 ∝x 3/5 , D 0 ∝x 7/5 . In this case, the mean temperature difference and maximum temperature difference are…”

Section: Elemental Optimizationmentioning

confidence: 99%

“…However, using the maximum temperature difference minimization in [24], the optimal construct of the first-order assembly is H 1 ∝x…”

Section: Elemental Optimizationmentioning

confidence: 99%

“…The results showed that the minimum maximum thermal resistance of the assembly which was obtained by assembling the lastorder assemblies could be obtained by changing the cross-section of high-conductivity link at the same assembly's order. Assuming that the hot spots were distributed along the boundary uniformly and taking the minimization of maximum temperature difference as optimization objective, Neagu and Bejan [24] optimized the tapered element and high-conductivity link and obtained the optimized structure that leads to a uniform temperature field in the inner element. In addition, they showed that the minimum thermal resistance decreases by 33% compared with that obtained in [1], and by 29% compared with that when only the variable cross-section high-conductivity link was optimized.…”

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confidence: 99%

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Constructal entransy dissipation rate minimization for heat conduction based on a tapered element

2011

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Based on constructal theory, the structure of a tapered element and high-conductivity link is optimized by taking the minimization of the entransy dissipation rate as the optimization objective. The results show that the mean temperature difference of the heat transfer cannot always decrease when the internal complexity of the control-volume increases. There exists an optimal constructal order leading to the minimum mean temperature difference for heat transfer. The thermal current density in high-conductivity links with variable shapes does not linearly depend on the length. Therefore, the optimized constructs based on the minimization of the entransy dissipation rate are different from those based on the minimization of the maximum temperature difference. Compared with the construct based on the minimization of the maximum temperature difference, the construct based on the minimization of the entransy dissipation rate can reduce the mean temperature difference, and improve the heat transfer performance significantly. Because entransy describes the heat transfer ability more suitably, various constructal problems in heat conduction may be addressed more effectively using this basis.constructal theory, entransy dissipation rate, volume-to-point heat conduction, generalized thermodynamic optimization Citation:Xiao Q H, Chen L G, Sun F R. Constructal entransy dissipation rate minimization for heat conduction based on a tapered element. Chinese Sci Bull, 2011Bull, , 56: 2400Bull, −2410Bull, , doi: 10.1007 Many of the volume-to-point flows that occur in nature are shaped like tree networks. These flows include river basins and formative processes of cay. A volume-to-point heat conduction problem in engineering is the determination of the optimal distribution of a high-conductivity material through a finite volume, which results in the heat generated at every point being transferred most effectively to the boundary of the medium. Constructal theory was put forward by Bejan [1] and was applied to the optimization of the volume-to-point heat conduction problem. To obtain better heat transfer structure, many scholars [2-15] have made researched conduction elements with different shapes and have used various optimization objectives based on constructal theory. Minimization of the maximum temperature difference is one of the most common optimization objectives. Bejan [1] used the minimization of the maximum temperature difference as the optimization objective and assumed that the amount of high-conductivity material needed was finite. First, the rectangular element was optimized and the corresponding optimal elemental shape (aspect ratio) was obtained. Then, the first-order assembly that was designed with a number of optimized elemental volumes was optimized. There exists an optimal shape for the first-order assembly (or the number of the rectangular elements) that corresponds to the minimization of the maximum temperature difference of the first-order assembly. The analogy continues until the control volume is rec...

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Section: Elemental Optimizationmentioning

confidence: 99%

mentioning

confidence: 95%

Section: Elemental Optimizationmentioning

confidence: 99%

“…However, using the maximum temperature difference minimization in [24], the optimal construct of the first-order assembly is H 1 ∝x…”

Section: Elemental Optimizationmentioning

confidence: 99%

mentioning

confidence: 99%

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Constructal entransy dissipation rate minimization for heat conduction based on a tapered element

2011

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Drones, automatic counting tools, and artificial neural networks in wildlife population censusing

Marchowski

2021

Ecology and Evolution

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The use of a drone to count the flock sizes of 33 species of waterbirds during the breeding and non‐breeding periods was investigated. In 96% of 343 cases, drone counting was successful. 18.8% of non‐breeding birds and 3.6% of breeding birds exhibited adverse reactions: the former birds were flushed, whereas the latter attempted to attack the drone. The automatic counting of birds was best done with ImageJ/Fiji microbiology software – the average counting rate was 100 birds in 64 s. Machine learning using neural network algorithms proved to be an effective and quick way of counting birds – 100 birds in 7 s. However, the preparation of images and machine learning time is time‐consuming, so this method is recommended only for large data sets and large bird assemblages. The responsible study of wildlife using a drone should only be carried out by persons experienced in the biology and behavior of the target animals.

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Constructal tree-shaped paths for conduction and convection

Bejan

2003

Int. J. Energy Res.

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SUMMARYThis lecture reviews a series of recent results based on the geometric minimization of the resistance to flow between one point (source, sink) and a volume or an area (an infinity of points). Optimization is achieved by varying the geometric features of the flow path subject to volume constraints. The method is outlined by using the problem of steady volume-point conduction. Optimized first is the smallest elemental volume, which is characterized by volumetric heat generation in a low-conductivity medium, and one-dimensional conduction through a high-conductivity 'channel'. Progressively larger volumes are covered by assemblies of previously optimized constructs. Tree-shaped flow structures spring out of this objective and constraints principle. Analogous problems of fluid flow, and combined heat and fluid flow (convection, trees of fins) are also discussed. The occurrence of similar tree structures in nature may be reasoned based on the same principle (constructal theory) (Bejan, 2000).

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Constructal-theory tree networks of “constant” thermal resistance

Cited by 92 publications

References 8 publications

Constructal entransy dissipation rate minimization for heat conduction based on a tapered element

Constructal entransy dissipation rate minimization for heat conduction based on a tapered element

Drones, automatic counting tools, and artificial neural networks in wildlife population censusing

Constructal tree-shaped paths for conduction and convection

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