Experimental Demonstration of Thermal Chameleonlike Rotators with Transformation-Invariant Metamaterials

Abstract

Heat flux rotation has important significance in thermal protection since it can shield the heat energy from a selected direction. Combining with tailored metamaterials, transformation thermotics provides a powerful way to manipulate heat flux, and various kinds of thermal meta-devices have been designed including thermal rotator. However, the existing transformation-thermotics-based thermal rotator can only work in a fixed background. Remanufacturing is inevitable when background changes, which is inconvenient and restricts the practical application. Here, we propose a novel mechanism for chameleonlike thermal rotator. The designed rotator can adaptively change its thermal conductivity with the object nearby while rotating heat flux without distorting the background temperature profile, just like a chameleon in nature. Moreover, such rotator is made of transformation-invariant material, thus its constitutive parameters do not change under arbitrary coordinate transformations. Therefore, the proposed rotator also has functionality-invariance beyond shape adjustment, and can theoretically transfer heat flux in arbitrary direction using different shapes of the same material. A prototype rotator was designed and fabricated, and its chameleonlike behavior is successfully demonstrated. Our concept provides a guidance to design chameleonlike thermal meta-devices and can be extended to other fields like acoustics, hydrodynamics, etc. The chameleonlike thermal rotator will have potential applications for the implementation of adaptive and adjustable metamaterials.

A Conceptual Review of the Potential of Cool Roofs as an Effective Passive Solar Technique: Elaboration of Benefits and Drawbacks

“…There are somewhat differing descriptions for cold materials. Whereby, cold materials must have a solar reflectance originally equal to or greater than 0.65 for ES-ENERGY STAR (Yang et al, 2020). After 3 years, its requirement is higher than 0.50, while APEC Energy Working Group (De Masi et al, 2018) recognized having at least a reflectance of 0.70 and a thermal emissivity of 0.75.…”

“…Advantages • reduce heat gain through the roof and enhance thermal comfort for indoor spaces. (Rabah, 2005;Chang et al, 2008;Razykov et al, 2011;Sadineni et al, 2011;Kamal, 2012;Al-Obaidi et al, 2014;Azari, 2014;Lotfabadi, 2015;Zingre et al, 2015a;Abdul Mujeebu and Alshamrani, 2016;Kannan and Vakeesan, 2016;Marrana et al, 2017;Pisello, 2017;Vickers, 2017;Shafique and Kim, 2017;Testa and Krarti, 2017;Ashraf et al, 2018;De Masi et al, 2018;Hu and Yu, 2019;Yang et al, 2020;Rawat and Singh, 2021a;Rawat and Singh, 2021b) • reducing cooling loads, minimizing demand for air conditioning and thus reducing energy bills. (Rosenfeld et al, 1998;Bilgiç, 2003;Cheikh and Bouchair, 2008;Suehrcke et al, 2008;Razykov et al, 2011;Singh et al, 2011;Akbari and Matthews, 2012;Kamal, 2012;Azari, 2014;Al-Obaidi et al, 2014;Lotfabadi, 2015;Zingre et al, 2015a;Abdul Mujeebu and Alshamrani, 2016;Akbari and Kolokotsa, 2016;Kannan and Vakeesan, 2016;Marrana et al, 2017;Shafique and Kim, 2017;Pisello, 2017;…”

“…(Rosenfeld et al, 1998;Al-Obaidi et al, 2014;Lotfabadi, 2015;Abdul Mujeebu and Alshamrani, 2016;Shafique and Kim, 2017;Ashraf et al, 2018;Hu and Yu, 2019) • decrease the peak electricity demand. (Bilgiç, 2003;Rabah, 2005;Cheikh and Bouchair, 2008;Suehrcke et al, 2008;Sadineni et al, 2011;Singh et al, 2011;Kamal, 2012;Azari, 2014;Lotfabadi, 2015;Zingre et al, 2015a;Abdul Mujeebu and Alshamrani, 2016;Kannan and Vakeesan, 2016;Marrana et al, 2017;Testa and Krarti, 2017;Vickers, 2017;Ashraf et al, 2018;Imran et al, 2018;Pradhan et al, 2019;Yang et al, 2020) • prevent urban heat island effect (UHI) and decelerate smog formation by reducing local air temperature. (Rosenfeld et al, 1998;Bilgiç, 2003;Haberl et al, 2004;Cheikh and Bouchair, 2008;Suehrcke et al, 2008;Singh et al, 2011;Saadatian et al, 2013;Al-Obaidi et al, 2014;Azari, 2014;Abdul Mujeebu and Alshamrani, 2016;Akbari and Kolokotsa, 2016;Pisello, 2017;Testa and Krarti, 2017;Ashraf et al, 2018;Besir and Cuce,...…”

“…Compared to the estimates from reported studies, one agent that may decrease the disadvantages of cool roofs is the buildup of snow on roofs during winter seasons. (Hosseini et al, 2018) Sources (Urban and Roth, 2010;Shafique and Kim, 2017) ( Santamouris et al, 2011;Testa and Krarti, 2017) (Chang et al, 2008;Synnefa et al, 2012) (Akbari and Levinson, 2008;Abdul Mujeebu and Alshamrani, 2016) (Pisello and Cotana, 2014;Hu and Yu, 2019) (Razykov et al, 2011;Kolokotroni et al, 2013) (Rosenfeld et al, 1998;Akbari et al, 2001) ( Lotfabadi, 2015;Xamán et al, 2017) ( Pisello and Cotana, 2014;Yang et al, 2020) (Konopacki et al, 1998;Kannan and Vakeesan, 2016) (Rosenfeld et al, 1998;Frontini et al, 2012) (Taha et al, 1999;De Masi et al, 2018) (Parker et al, 1998;Imran et al, 2018) ( Cheikh and Bouchair, 2008;Jo et al, 2010) (Synnefa et al, 2007;Suehrcke et al, 2008) (Synnefa et al, 2007;Marrana et al, 2017) ( Xu et al, 2012;Rawat and Singh, 2021b) (Oleson et al, 2010;Lamnatou and Chemisana, 2015) (Sadineni et al, 2011;Pradhan et al, 2019)…”

Chemical-diffusion Metamaterials with “Plug and Switch” Modules for Ion Cloaking, Concentrating and Selection: Design and Experiments

“…It controls the path of electromagnetic wave transport to achieve invisibility through an inhomogeneous medium artificially designed by the theories of transformation optics 1 (TO) by Pendry and scattering cancellation 2 (SC) by Engheta. In addition to the ideal cloaking proposed by theory and demonstrated by experiments, the design is further extended to metamaterials with diversified functions such as concentrators 3,4 , rotators 5,6 and illusion metamaterials 7,8 . After great success in manipulating electromagnetic waves [9][10][11] , TO and SC were also proven to be powerful tools to manipulate not only other wave-based fields like acoustic waves [12][13][14] and water waves 15,16 but also diffusion fields such as thermal flux [17][18][19][20][21][22][23][24][25] , electric fields [26][27][28][29] , magnetic fields [30][31][32][33][34] , diffusive light [35][36][37] and chemical fields [38][39][40][41][42][43] .…”