Thermostat property of Janus emitter in enclosures

Abstract

Passive radiative cooling has been spotlighted as a method to solve environmental problems and fuel depletion. Therefore, various radiative coolers have been studied and applied to lower the surface temperatures of objects such as roof, building exterior, solar cells, and automobiles without any external energy. Furthermore, recently, the research scope of radiative cooling is expanded to enclosed spaces, which is not limited to object cooling. Especially, a Janus emitter (JET) which has selective and broadband emission on the separated sides, helps drawing the heat from enclosures efficiently. Using JET enables better cooling of enclosed space in hot weather than conventional emitter, which considers the only emissivity of top side, however, the cooling capability in some cases, that cooling is not required (i.e., night and winter), should be demonstrated for practical applications. This study analyzes the space cooling performance of JET in hot and cool conditions (e.g., day and night). The cooling tendencies with different sizes of enclosed space were also confirmed by heat transfer analysis. Furthermore, systematic experiments with various sized emitters demonstrate the space cooling capability of JET in different conditions (i.e., temperature and volume). These successful demonstrations prove the thermalmanaging property of JET regardless of chamber volumes.