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  • 1
    Publication Date: 2021-10-13
    Description: A comprehensive understanding of the combined effects of surface roughness and wettability on the dynamics of the trapping process is lacking. This can be primarily attributed to the contradictory experimental and numerical results regarding the impact of wettability on the capillary trapping efficiency. The discrepancy is presumably caused by the surface roughness of the inner pore-solid interface. Herein, we present a comparative μ-CT study of the static fluid-fluid pattern in porous media with smooth (glass beads) and rough surfaces (natural sands). For the first time, a global optimization method was applied to map the characteristic geometrical and morphological properties of natural sands to 2-D micromodels that exhibit different degrees of surface roughness. A realistic wetting model that describes the apparent contact angle of the rough surface as a function surface morphology and the intrinsic contact angle was also proposed. The dynamics of the trapping processes were studied via visualization micromodel experiments. Our results revealed that sand and glass beads displayed opposite trends in terms of the contact angle dependence between 5° and 115°. Sand depicted a nonmonotonous functional contact angle dependency, that is, a transition from maximal trapping to no trapping, followed by an increase to medium trapping. In contrast, glass beads showed a sharp transition from no trapping to maximal trapping. Since both porous media exhibit similar morphological properties (similar Minkowski functions: porosity, surface density, mean curvature density, Euler number density), we deduce that this difference in behavior is caused by the difference in surface roughness that allows complete wetting and hence precursor thick-film flow for natural sands. Experimental results on micromodels verified this hypothesis.
    Keywords: 550.724 ; impact of wettability on trapping efficiency ; impact of surface roughness and pore space structure on trapping efficiency ; porous media with rough surface ; natural sand and glass ceramic micromodels ; wettability-controlled crossover from snap-off to bypass trapping ; spontaneous precursor thick-film flow (Wenzel's argument)
    Language: English
    Type: map
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  • 2
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    Stockholm : Europ. Council for an Energy Efficient Economy | Wuppertal : Wuppertal Institut für Klima, Umwelt, Energie
    Publication Date: 2022-02-18
    Description: Iran is one of the largest oil producers and natural gas owners globally. However, it has to struggle with domestic energy shortages, economic losses through energy subsidisation and inefficient energy infrastructures. Furthermore, GHG and other energy related emissions are rapidly increasing and posing a growing threat to local environment as well as global climate. With current trends prevailing, Iran may even become a net energy importer over the next decades. Resource allocation is therefore a crucial challenge for Iran: domestic consumption stands versus exports of energy. The energy transformation sector clarifies Iran's dilemma: soaring electricity demand leads to blackouts, and power plant new builds are far from using most efficient technologies (e. g. CHP), therefore keeping energy intensive structures. But fossil fuels could be sold on international markets if spared by having more efficient energy infrastructures. As shown by the high energy intensity of its economy, Iran has large potentials for energy saving and efficiency. In order to highlight and better identify this potential the paper contrasts a high efficiency scenario in all sectors of energy transformation and consumption with a possible "business as usual" development. Using a bottom-up approach, the analysis provides a sector-by-sector perspective on energy saving potentials. These can be utilised on the demand side especially in the transport sector (fuels) and in households (electricity for appliances, natural gas for heating). Electricity generation bears efficiency potentials as well. We conclude that Iran, but also the international community, would benefit on various levels from a more energy-efficient Iranian economy: Energy exports could increase, generating more foreign currency and reducing the pressures on international oil and gas prices; energy consumption would decrease, leading to lower needs for nuclear energy and for subsidies to Iranian people, as well as to a reduction of the high external costs entailed by fossil fuels combustion (smog in cities, environmental stress).
    Keywords: ddc:330
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
    Type: conferenceobject , doc-type:conferenceObject
    Format: application/pdf
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