Control Of Near Field Radiative Heat Transfer By Anisotropic Media And Its Application In Thermophotovoltaics

In recent years,with the development of nanotechnology,the heat transfer problem in the field of nanoscale has become particularly important.At the nanometer distance,the limit value of radiation heat transfer between two bodies given by Planck's law is defied.At the same time,the radiation heat transfer generated by the contribution of coupling evanescent wave will be far greater than this limit value.This phenomenon is therefore called as near field radiation heat transfer.Immerse near-field radiation heat flux has contributed to the development of nano thermal devices for a long time and one's attention focuses on how to further enhance the near field radiation heat transfer.Nevertheless,in order to make the near-field thermal devices have more functional value in practice,the near field radiation heat transfer must be in a reasonable manner to tune and control.Thus the anisotropic medium is a good way to achieve near-field thermal management.Based on the derivation process of near-field radiation heat transfer formulation between two isotropic parallel plates in this article,and then focusing on the situation of radiative heat transfer between two anisotropic slabs and the Maxwell Equations of anisotropic media are rededuced.After that,the 4?4 matrix describing the characteristics of electromagnetic wave reflection and transmission process is obtained and the electromagnetic field boundary conditions are applied to calculate the transmission matrix simultaneously.The radiative heat exchange of the two anisotropic plates is finally acquired.The radiation transfer characteristics of anisotropic materials including magnetooptical materials,hyperbolic metamaterials and graphene-hyperbolic metamaterial's heterostructures are analyzed and calculated by using the proposed formulation of radiation heat transfer between anisotropic media.It is found that the near field heat flow can be actively controlled by tuning the intensity and direction of magnetic field,the tilt direction of optical axis and the number of heterogeneous junctions,respectively.Besides,2D metasurface is proposed to make up for the defects of plate structures in terms of medium loss existing in dielectric film and bulk.By changing magnetic field of grapehene and relative rotation angle of uniaxial metasurface,the characteristics of radiation heat transfer are analyzed and calculated respectively,and it is also found that 2D metasurface can effectively manage heat flow.This paper further utilizes the strategy of tilting hyperbolic metamaterial optical axis to effectively improve the low efficiency of near-field thermophotovoltaic device,which consists of the boron nitride as the hot source and graphene-indium antimonide of heterostructure as the cell.The results show that titled optical axis can not only greatly suppress the low band gap energy spectral heat flux but also increase the heat flux occurring in the high band gap.Finally,the effects of heat source temperature,battery temperature,working voltage and graphene chemical potential on the output power and efficiency of thermal photovoltaic cells are discussed.