Macroscopic Heat Flow Regulation Based On Thermal Metamaterials

As a new material developed since 2008,thermal metamaterials have shown many thermal functions and properties beyond traditional materials,and have attracted extensive attention since its birth.Thermal metamaterials can be used to regulate the size and the direction of heat flow,realize many novel thermal functions and devices,and improve the efficiency of heat transfer.In view of the problems that the types and functions of current metamaterials are not perfect enough,this paper makes innovations in expanding metamaterials,exploring adaptive thermal camouflage devices and detecting methods of metamaterials.The concept of transmitting encrypted infrared information was proposed.The regionalization transformation method was used to divide a region into several sub-regions,and coordinate transformation was carried out in each sub-region to change the position,size,shape and rotation angle of the real target,leaving infrared traces.Through proper splicing,these strokes would constitute infrared information,which can only be "decoded" with an infrared camera.Based on energy harvesting unit and energy shielding unit,the possibility of thermal diodes with high transient rectification ratio was explored.The diodes delivered heat asymmetrically similar to the asymmetric current characteristics of electrical diodes and light-emitting diodes.Through finite element simulation,the transient thermal rectification ratio was as high as 50,which was a great breakthrough in the existing research.An adaptive thermal camouflage method was proposed by adjusting the heat conduction outside the plane.Through mathematical derivation,the basic design principle of synchronous transient heat conduction along the background plate and the camouflage device was obtained,and the material and shape of the camouflage device and the background plate were constrained.Through finite element simulation,it was proved that the camouflage device and the background plate could conduct heat synchronously.A method for detecting hot metamaterial structures by flying laser point was presented.The relationship between the thermal dissipation behavior of the dynamic hot spots corresponding to the flying laser points and the thermal metamaterials was explained by taking the ideal thermal cloak,the thermal concentrator and the thermal rotator as examples.The three thermal structures on the plane were identified successfully,and the influence of the radius of the laser points on the detection ability was discussed.The method can be used for edge detection,developing transient imaging analyzer and anti-functional structure.