A near-field radiative heat transfer device

Abstract

Recently, many works have experimentally demonstrated near-field radiative heat transfer (NFRHT) exceeding the far-field blackbody limit between planar surfaces [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] . Due to the difficulties associated with maintaining the nanosize gaps required for measuring a nearfield enhancement, these demonstrations have been limited to experiments that cannot be implemented into actual applications. This poses a significant bottleneck to the advancement of NFRHT research. Here, we describe devices bridging laboratory-scale measurements and potential NFRHT engineering applications in energy conversion 16,17 and thermal management 18-20 . We report a maximum NFRHT enhancement of ~ 28.5 over the blackbody limit with devices made of millimeter-sized doped silicon (Si) surfaces separated by vacuum gap spacings down to ~ 110 nm. The devices capitalize on micropillars, separating the high-temperature emitter and low-temperature receiver, manufactured within micrometer-deep pits. These micropillars, which are ~ 4.5 to 45 times longer than the nanosize vacuum spacing where radiation transfer takes place, minimize parasitic heat conduction without sacrificing device structural integrity. The robustness of our devices enables gap spacing visualization via scanning electron microscopy (SEM) prior to *

Integrated near-field thermo-photovoltaics for heat recycling

“…arvesting of thermal energy can be performed using radiation from systems with hot surfaces by placing a cold photodetector at nanometer distances. At nanometer (near-field) distances, strong heat exchange occurs due to evanescent modes, thermal radiation that cannot propagate from the hot body towards the far-field, but can evanescently couple from a hot to a cold surface when the separation is sub-wavelength [1][2][3][4][5][6][7][8][9][10][11][12][13] . Near-field radiative heat exchange have been demonstrated to overcome the blackbody limit at small gaps (d) between the hot and cold surfaces and scales as 1/d α (1 ≤ α ≤ 2; α is a geometrydependent factor).…”

Thermionic-enhanced near-field thermophotovoltaics

“…These losses are not accounted for in this analysis because they could be minimized by practical means, e.g. by using tapered spacers with very small contact area [28], [29], and therefore, they do not represent a fundamental source of losses of this concept.…”

“…Sub-micron separation distances have been also experimentally realized in the frame of near-field thermal radiation experimentations [25]- [28]. Current research efforts target the use of such nanospacers into nTPV devices [29]. The proposed conceptual device will eventually take advantage of all these developments, which are directly transferrable to the experimental implementation of nTiPV devices.…”

Near-Field Radiative Heat Transfer between Dissimilar Materials Mediated by Coupled Surface Phonon- and Plasmon-Polaritons

“…The heat flux meter has been calibrated by measuring the thermal resistance of 1.1-mm-thick borosilicate glass having a known thermal conductivity of 0.94 Wm -1 K -1 . 21 All experiments have been conducted in a vacuum chamber with a pressure of ~ 10 -4 Pa under a class 1000 clean room tent.…”

“…Rr are the thermal resistances of the grease, the emitter, and the receiver, while Rrad and Rcond are21 the thermal resistances due to NFRHT in the vacuum gap spacing and conduction through the SiO2 nanopillars.…”