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Browsing by Person "Barfuss, Isabel"

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    Biogas production vs. dung combustion as household energy in rural Ethiopia
    (2011) Müller, Joachim; Barfuss, Isabel; Gwavuya, Stanley; Abele, Steffen
    The objective of the study was to investigate the potential of dung as primary and secondary energy source, i.e. direct combustion of dung and combustion of its secondary products biogas or dried digestate, under consideration of its quality as fertilizer. The results of the analysis show the similarity of dung and digestate regarding combustion characteristics. Fertilizer values proved better for digestate. However, calorific value of dung proved much lower than those of biogas. Thus, biogas represents a good alternative energy source with double benefit. Besides its better combustion characteristics compared to dried dung, it also delivers a superior fertilizer.
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    Modelling of air resistance during drying of wood-chips
    (2011) Müller, Joachim; Karaj, S.; Barfuss, Isabel; Schalk, J.; Reisinger, G.; Pude, R.
    The objective of this study was to investigate the parameters that affect the drying process of wood chips at low air flow conditions. This objective was determined by measuring the air pressure resistance being produced by wood chips by examining different variables such as: air flow rate, air velocity, wood chip size, bulk density, bulk height and porosity. The air flow resistance was measured inside a 3 meter high cylindrical air duct constructed at University of Hohenheim. Physical properties of two different Spruce wood chip fractions were analyzed and their characteristics were considered on fitting the model expression. The analysed model expresses the physical behaviour of air flow resistance. Statistical analyses show high correlation of air speed versus air flow resistance. The model could be used for determination of drying conditions with low air mass flow. The height of bulk density according air mass flow generated or the necessary air mass flow needed for transporting air through the bulk height.