Breaking efficiency limit of thermal concentrators by conductivity couplings  

作　　者：Pengfei Zhuang Liujun Xu Peng Tan Xiaoping Ouyang Jiping Huang 

机构地区：[1]Department of Physics,State Key Laboratory of Surface Physics,and Key Laboratory of Micro and Nano Photonic Structures(MOE),FudanUniversity,Shanghai200438,China [2]Department of Physics and State Key Laboratory of Surface Physics,Fudan University,Shanghai 200438,China [3]School of Materials Scienceand Engineering,Xiangtan University,Xiangtan 411105,China

出　　处：《Science China(Physics,Mechanics & Astronomy)》2022年第11期68-77,共10页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. 11725521, and 12035004);the Science and Technology Commission of Shanghai Municipality (Grant No. 20JC1414700)。

摘　　要：The concentrating efficiency of a thermal concentrator can be reflected in the ratio of its interior to exterior temperature gradients,which, however, has an upper limit in existing schemes. Here, we manage to break this upper limit by considering the couplings of thermal conductivities and improve the concentrating efficiency of thermal concentrators. For this purpose, we first discuss a monolayer scheme with an isotropic thermal conductivity, which can break the upper limit but is still restricted by its geometric configuration. To go further, we explore another degree of freedom by considering the monolayer scheme with an anisotropic thermal conductivity or by adding the second shell with an isotropic thermal conductivity, thereby making the concentrating efficiency completely free from the geometric configuration. Nevertheless, apparent negative thermal conductivities are required, and we resort to external heat sources realizing the same effect without violating the second law of thermodynamics. Finite-element simulations are performed to confirm the theoretical predictions, and experimental suggestions are also provided to improve feasibility. These results may have potential applications for thermal camouflage and provide guidance to other diffusive systems such as static magnetic fields and dc current fields for achieving similar behaviors.

关 键 词：thermal concentrator concentrating efficiency conductivity coupling apparent negative conductivity 

分 类 号：O551[理学—热学与物质分子运动论]