Nanoscaled Metamaterial as an Advanced Heat Pump and Cooling Media

Abstract

(1 of 10) 1600008 wileyonlinelibrary.com amount of energy spent from the external source, [3][4][5] and hence, the heat pumps are much more effi cient than the simple heating devices. The second important feature of the heat pump is the ability to lower the temperature of the cooler body by transferring the heat to a warmer side, i.e., in the direction opposite to the spontaneous heat fl ow. These two features determine the use of heat pumps, and specify the potential niche for their applications on the future techniques.The most conventional heat pumps are based on the thermodynamic cycle involving compression and expansion of the gaseous working medium. Such devices are essentially large complex technical systems consisting of several sub-systems such as electrical motors, compressors, expanders, heat exchangers, etc. They are currently used for various applications ranging from the higheffi cient heating and cooling household premises [ 6,7 ] and industrial buildings [ 8,9 ] to agriculture, [ 10 ] food industry, [ 11 ] and space technology. [ 12,13 ] Other types of heattransfer systems such as adsorption, [ 14 ] molecular, [ 15 ] and chemical [ 16 ] heat pumps also demonstrate high cost and limited effi ciency, especially at nanoscale. For example, the thermoelectric microrefrigerators [ 17 ] can allow the cooling by several Kelvins at the power density of about 100 W cm −2 , and only 1 K at 400 W cm −2 . [ 18 ] It is expected that the rate of heat pumps in the private and industrial heat and cooling systems will reach 30% by 2050. [ 19 ] The main problem retarding the wide application of heat pumps for heating is the complicity and large size, and hence, the high cost and long payout period. [ 20 ] Besides, the compression-based systems cannot operate at high temperatures. These features also impede the application of heat pumps in the miniaturized devices which are of a great importance now, such as electronics, semiconductor-based energy transforming devices, [ 21 ] advanced solar cell systems, [ 22 ] nanomechanical systems, [ 23 ] miniaturized unmanned fl ying vehicles, cubesats, [24][25][26] and other small-sized spacecraft and their power systems. [ 27 ] Some of these problems can be overcome by creating materials displaying properties that do not exist in nature, i.e., metamaterials, [ 28 ] i.e., the "transition from the compression-based system to a material-based form-factor" should be achieved. [ 29 ] Apparently, this is not possible in the framework of the obsolete Nanoscaled Metamaterial as an Advanced Heat Pump and Cooling MediaIgor Levchenko ,* Isak I. Beilis , and Michael Keidar Major characteristics of the nanoscaled high-temperature metamaterial capable of reversal heat transmission are calculated, and two design variants are proposed and discussed. Specifi cally, the basic design has been proposed involving the solid-state highly emissive cathode material, and the modifi cation with a liquid-state emissive material (e.g., cesium) fi lling the nanoporous structure such as previously synthesize...

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