Biomorphous Silicon Carbide as Novel Loop Heat Pipe Wicks

Abstract

Biomorphous silicon carbide is tested as a novel wick material for flat evaporator loop heat pipes (LHP). The machinable ceramic gives the possibility to improve the wick performance by macroporous channel networks without closing the structure inherent microporosity. A minimum thermal resistance of 0.4236 C W À1 is obtained for unmodified SiC at a power input of 200 W. Modification with channels parallel to the evaporating surface results in an improved thermal resistance of 0.3792 C W À1 . Modification with channels perpendicular to the evaporating surface increases the thermal resistance to 0.4469 C W À1 , but reduces the necessary heat load for stable start-up from 50 to 25 W.

Advanced Hierarchical Biomorphous Silicon Carbide Monoliths

“…The removal of organic matter from the natural precursor by pyrolysis in an inert atmosphere leaves a carbon structure that retains the cellular structure of the original biological material, which can then be converted into the final SiC ceramic that has been of interest in recent decades. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Compared to conventional processing routes for cellular SiC ceramics such as the replica method [20][21][22] or sacrificial templating, [23][24][25][26] the biomorphous approach is a promising method for producing low-cost cellular carbide ceramics with a comparatively low sintering temperature. [27,28] Previous research has mostly been carried out with liquid Si infiltration of carbon precursors [1,15,29] above the melting temperature of Si (typically above 1450 °C), resulting in Si/SiC composites, as excess Si is required for complete conversion to SiC.…”

Experimental investigation of boiling regimes in a capillary-fed two-layer evaporator wick

“…The screen meshes contained smaller pore sizes that could enhance capillary pressure while the microchannels provided a high permeability liquid-feeding pathway from below. Weisenseel et al [18] employed silicon carbide wicks with horizontal vapor removal channels to reduce thermal resistance at the evaporator of loop heat pipes. In addition, lateral or columnar arteries that supply a thin layer of wick [19] as well as grid-patterned wicks [20,21] have all been shown to increase the dryout heat flux while reducing the surface superheat during capillary-fed boiling, as compared to homogeneous wicks.…”

Enhanced Liquid Propagation and Wicking Along Nanostructured Porous Surfaces

“…Inspired from water transpiration in plants, [1,2] capillary-fed evaporators are widely used for many industrial applications such as water filtration, [3,4] electronics cooling, [5][6][7] heating, ventilation, and air conditioning, [8][9][10] fuel cells, [11,12] and biomedical applications. [13] Due to its essential role in the earlier processes, passive capillary pumping, which effectively transports liquid through a wick without any need for external forces, has attracted broad interest.…”