Bilayer thermal harvesters for concentrating temperature distribution

Xu, Guoqiang; Zhou, Xue; Zhang, Jiayin

doi:10.1016/j.ijheatmasstransfer.2019.118434

Cited by 38 publications

(16 citation statements)

References 28 publications

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“…Similar to the thermal cloaking, small (near-zero) conductive region (such as epoxy, grease, etc.) is the prior choice to achieve approximate/enhanced temperature gradients in the design of (enhanced) transparency [18][19][20] (concentration [12][13][14][15] ). These behaviors of no or enhanced (approximate) temperature gradients can be observed with single homogeneous and finitely conductive materials.…”

Section: Resultsmentioning

confidence: 99%

“…arious kinds of metamaterials are emerging to meet the increasing demands on field manipulation. As a major diffusive member, thermal metamaterial reveals enormous potential on motivating the current thermal techniques, while the pioneering electromagnetic metamaterial of field invisibility 1,2 inspires the thermal analogs of thermal cloak [3][4][5][6][7][8][9][10][11] , concentration [12][13][14][15] , rotation 16,17 , (enhanced) transparency [18][19][20] , and illusion [21][22][23] . Static thermal metamaterials are mostly designed with natural materials, whose inherent conductivities only take some discrete digital values as illustrated in Fig.…”

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confidence: 99%

“…1a. For certain functionality, some new digital conductivities and specific inhomogeneities can be effectively realized through mixing natural thermal materials based on the transformation methods 1,[3][4][5][6][13][14][15]17,18,21,22,24 or scattering cancellation method 2,[7][8][9][10]12,16,[18][19][20] . Based on the conventional design principle, these new digital materials still possess non-tunable thermal conductivities and fixed anisotropies, which bring great challenges in the adjustment and functional switching of thermal manipulations.…”

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confidence: 99%

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Tunable analog thermal material

Dong

Liu

et al. 2020

Nat Commun

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Naturally-occurring thermal materials usually possess specific thermal conductivity (κ), forming a digital set of κ values. Emerging thermal metamaterials have been deployed to realize effective thermal conductivities unattainable in natural materials. However, the effective thermal conductivities of such mixing-based thermal metamaterials are still in digital fashion, i.e., the effective conductivity remains discrete and static. Here, we report an analog thermal material whose effective conductivity can be in-situ tuned from near-zero to near-infinity κ. The proof-of-concept scheme consists of a spinning core made of uncured polydimethylsiloxane (PDMS) and fixed bilayer rings made of silicone grease and steel. Thanks to the spinning PDMS and its induced convective effects, we can mold the heat flow robustly with continuously changing and anisotropic κ. Our work enables a single functional thermal material to meet the challenging demands of flexible thermal manipulation. It also provides platforms to investigate heat transfer in systems with moving components.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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Tunable analog thermal material

Dong

Liu

et al. 2020

Nat Commun

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“…[23][24][25][26] Researchers have then made great achievements on heat manipulation with various thermal metadevices. [27][28][29][30][31][32][33][34][35][36] The pioneering works mainly focused on regular shaped cloaks, i. e. cylindrical and spherical cloaks. Cloaks with more complicated boundaries were then studied in the field of electromagnetism and acoustics.…”

Section: Introductionmentioning

confidence: 99%

Non-Singular Homogeneous Polyhedral Heat Cloak and Its Realization

Chen¹,

Liang²,

Laude³

et al. 2019

ES Energy Environ.

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As most arbitrarily shaped cloaks can be approximated by polyhedra and further divided into a series of tetrahedra, we propose in this paper a linear mapping approach to design cloaks with tetrahedron shapes (i. e. tetrahedral cloaks). Homogeneous material properties of the cloak are straightforwardly obtained from coordinates of typical points. Consequently, most arbitrarily shaped thermal cloaks can be designed using homogeneous anisotropic materials only. We construct two polyhedral cloaks and show numerically that they successfully thermally conceal objects after a certain lapse of time. We then demonstrate that cloaks with curved boundaries can also be obtained using our approach. It is further shown how geometrical parameters affect the material properties and cloaking performances. One can flexibly tune the cloaking performances based on practical requirements and material availabilities. We analyze effectiveness of a polygonal cloak composed of an alternation of homogeneous isotropic layers, and note that cloaking deteriorates at short times. We finally sketch an approach to realize 3D homogenized thermal metamaterials.

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“…These two points benefit practical applications because thermal sensors do not have to be geometrically isotropic, and nonlinear thermal conductivity is common. In fact, bilayer scheme has achieved great success in designing thermal cloaks [13][14][15][16][17][18], thermal concentrators [19], and chameleonlike metashells [20,21]. Cloaks make the temperature gradient in the center zero; concentrators make the temperature gradient in the center steeper than that in the matrix; invisible sensors keep the same temperature gradient in the sensor and matrix.…”

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confidence: 99%

Theory for Invisible Thermal Sensors: Bilayer Scheme

Huang

2022

Transformation Thermotics and Extended Theories

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In this chapter, we propose a bilayer scheme with isotropic materials to design invisible thermal sensors with detecting accuracy. Therefore, the original temperature fields in the sensor and matrix can keep unchanged. By solving the linear Laplace equation with a temperature-independent thermal conductivity, we derive two groups of thermal conductivities to realize invisible thermal sensors, even considering geometrically anisotropic cases. These results can be directly extended to thermally nonlinear cases with temperature-dependent thermal conductivity, as long as the ratio between the nonlinear thermal conductivities of the sensor and matrix is a temperature-independent constant. These explorations are beneficial to temperature detection and provide insights into thermal camouflage.

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Bilayer thermal harvesters for concentrating temperature distribution

Cited by 38 publications

References 28 publications

Tunable analog thermal material

Tunable analog thermal material

Non-Singular Homogeneous Polyhedral Heat Cloak and Its Realization

Theory for Invisible Thermal Sensors: Bilayer Scheme

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