Dreyer, Michael E.
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Dreyer, Michael E.
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Dreyer, Michael E.
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Dreyer, M. E.
Dreyer, Michael
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Item type:Publication, Wicking into porous polymer-derived ceramic monoliths fabricated by freeze-castingSilicon oxycarbide monoliths of different pore size distribution were fabricated by freeze-casting. The samples revealed a lamellar pore structure with an axial anisotropy. To evaluate the capillary transport abilities we performed wicking experiments. The sample weight measurement method was applied during the imbibition. The samples show deviations in permeability from 10% to 49% at different sample orientations that quantifies the impact of the anisotropy in the axial direction. The deviations were larger for the samples with smaller pore size. For these samples we also observed larger differences in the wicking behaviour. The samples with bigger pore size demonstrated higher permeability and faster wicking. Imbibition results at both sample orientations showed a good agreement with a prediction via the Lucas–Washburn equation with gravity effects. We demonstrate hereby, that our approach of macroscopic modelling predicts wicking behaviour in anisotropic structures reasonably well, providing a simple tool for further porous material investigations.journal articleBand:37Heft:5101 93 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Investigation on cryo-wicking performance within metallic weaves under superheated conditions for screen channel liquid acquisition devices (LADs)In order to investigate the wicking performance of cryogenic propellants within metallic screens for space liquid acquisition devices (LADs), a vertical wicking experiment was carried out in a one-species test system with liquid nitrogen (LN2). Screens of Dutch twill weave (DTW) type 200 × 1400 were tested in both warp and shute directions. Two different degrees of superheat (∼2 K and ∼25 K) were achieved with a novel porous cooling shield element. A modified one-dimensional macroscopic model is proposed which considers the thermal effect of the solid weave and the vapor environment. Good agreement with experimental data is achieved. Results show that the cryo-wicking process is sensitive to the superheat condition. The wicking velocity as well as the maximum wicking height decreases with increasing superheat. For the same superheat condition, the wicking velocity was always higher in the warp direction than that in the shute direction.journal articleBand:141102 118 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Wicking of liquid nitrogen into superheated porous structuresEvaporation in porous elements of liquid–vapor separation devices can affect the vapor-free cryogenic propellant delivery to spacecraft engines. On that account, the capillary transport of a cryogenic liquid subjected to evaporation needs to be understood and assessed. We investigate wicking of liquid nitrogen at saturation temperature into superheated porous media. A novel test facility was built to perform wicking experiments in a one-species system under non-isothermal conditions. A setup configuration enabled to define the sample superheat by its initial position in a stratified nitrogen vapor environment inside the cryostat. Simultaneous sample weight and temperature measurements indicated the wicking front velocity. The mass of the imbibed liquid nitrogen was determined varying the sample superheat, geometry and porous structure. To the author’s extent of knowledge, these are the first wicking experiments performed with cryogenic fluids subjected to evaporation using the weight–time measurement technique. A one-dimensional macroscopic model describes the process theoretically. Results revealed that the liquid loss due to evaporation at high sample superheats leads to only a slight imbibition rate decrease. However, the imbibition rate can be greatly affected by the vapor flow created due to evaporation that counteracts the wicking front propagation.journal articleBand:78113 116