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Burheim O.S.,Norwegian University of Science and Technology | Pharoah J.G.,Queens University | Lampert H.,RWTH Aachen | Vie P.J.S.,IFE | Kjelstrup S.,Norwegian University of Science and Technology
Journal of Fuel Cell Science and Technology | Year: 2011

We report the through-plane thermal conductivities of the several widely used carbon porous transport layers (PTLs) and their thermal contact resistance to an aluminum polarization plate. We report these values both for wet and dry samples and at different compaction pressures. We show that depending on the type of PTL and the existence of residual water, the thermal conductivity of the materials varies from 0.15 W K-1 m-1 to 1.6 W K-1 m-1, one order of magnitude. This behavior is the same for the contact resistance varying from 0.8 m 2 K W-1 to 11× 10-4 m2 K W-1. For dry PTLs, the thermal conductivity decreases with increasing polytetrafluorethylene (PTFE) content and increases with residual water. These effects are explained by the behavior of air, water, and PTFE in between the PTL fibers. It is also found that Toray papers of differing thickness exhibit different thermal conductivities. © 2011 American Society of Mechanical Engineers. Source


de Lima A.A.,IFE | Alvarenga M.A.R.,Federal University of Lavras | Rodrigues L.,Federal University of Lavras | Chitarra A.B.,Federal University of Lavras
Horticultura Brasileira | Year: 2011

The aim of this work was to evaluate the yield and quality of tomato fruits, hybrid "Vênus", produced on substrates and with application of nutrient solution and humic acids (AH). Four doses of AH were evaluated (0, 20, 40 and 80 L ha-1) and 4 substrates: S1 (coconut fiber (CF)), S2 (FC + carbonized coffee husk (CC) in the ratio 1:3), S3 (CF + CC in the ratio 2:3) and S4 (CC), were evaluated following the randomized blocks design in factorial 4×4 scheme with four replications. The 35-day old seedlings were transplanted into plastic bags of 7 L. The humic acids were applied four times in eight-day intervals, and the first application was carried out eight days after transplanting. There was no significant effect of AH on the yield and quality of fruit, except in relation to soluble solids (SS)/titratable acidity (AT). Doses of up to 36 L ha-1, increase the AT, above that amount favored increase of SS. The carbonized coffee husk in treatments S2, S3 and S4, did not alter the production of small fruits, medium, non-commercial, moisture, pH, SS, AT and SS/AT, however, significantly reduced the total production, commercial and large size fruit. The production of fruits in S1 was significantly higher compared to the other treatments, with an average of 142.6 t ha-1, showing average increase in yield of 24.4%, 29.3% and 36.1% compared to plant of treatments S2, S3 and S4, respectively. Source


de Lima A.A.,IFE | Alvarenga M.A.R.,Federal University of Lavras | Rodrigues L.,Federal University of Lavras | de Carvalho J.G.,Federal University of Lavras
Horticultura Brasileira | Year: 2011

We evaluated the nutritional status and yield of tomato hybrid "Vênus", grown on substrates, with application of humic acids (AH) and fertigation. Four doses of AH (0, 20, 40 and 80 L -1 ha) and four substrates: S1 (coconut fiber (CF)), S2 (FC + carbonized coffee husk (CC) in the ratio 1:3), S3 (CF + CC - in the ratio 2:3) and S4 (CC) were evaluated following the randomized blocks design in factorial 4x4 scheme with four replications. The 35-day old seedlings were transplanted into plastic bags of 7 L. The humic acids were applied four times in eight-day intervals, and the first application was carried out eight days after transplanting. There was no significant effect of the treatments on the content of N, K and S in leaves and on non-marketable fruits yield. However, there was a significant effect of the substrates on the content of P, Ca, Mg and on the total and marketable fruit yield. Increasing doses of AH reduced linearly the content of B and Cu (on S1), but increased the content of Zn in leaves. Humic acid doses of 31 to 49 L ha -1 provided the highest contents of Fe, Cu, and the lowest content of Mn. The highest marketable yields were obtained using coconut fiber, with an average of 5.6 kg/plant, showing an average yield increase of 22.9%, 38.7% and 49.7% in comparison to S2, S3 and S4, respectively. Source


Kuehn D.,NORSAR | Dahm T.,German Research Center for Geosciences | Wangen M.,IFE | Heimann S.,German Research Center for Geosciences
5th EAGE Passive Seismic Workshop: From Wish List to To-Do List | Year: 2014

Human-induced earthquakes are more and more brought into the focus of public attention. E. g. Ellsworth (2013) attracts notice to the dramatic increase of the number of earthquakes in the central and eastern United States over the past few years. Environments prone to induce or trigger seismicity are numerous, e. g. oil and gas exploration sites, large-scale surface quarries and mines, Enhanced Geothermal Systems (EGS), dam sites and injections of e.g. CO2 or waste water. Since the nature of induced and triggered earthquakes implies their occurrence near engineering activity, even earthquakes of small magnitude are a cause for concern. We present several numerical methods to enhance the understanding of the spatial and temporal occurrence of seismicity, which has been triggered or induced by human operations: A) poroelastic modelling employing elementary Green's functions, b) analytical fracture model combined with a rate- And state- dependent constitutive model and c) a 3D FEM able to handle both heterogeneous rocks and branched fractures. Source


Hoyer N.,SPT Group | Kirkedelen M.B.,SPT Group | Biberg D.,SPT Group | Johnson G.W.,Statoil | And 3 more authors.
BHR Group - 16th International Conference on Multiphase Production Technology 2013 | Year: 2013

In order to provide the flow assurance engineer with a more general workflow to assess prediction uncertainties we are in this work proposing a new method to specify flow model uncertainties. First we have reviewed a comprehensive database of laboratory measurements of primarily pressure drop and holdup. Datasets are grouped according to flow conditions. The most significant flow model parameters for each group are identified and then for a subset of the database tuned to each individual measurement simultaneously. Results from sensitivity analysis and uncertainty quantification are discussed. Furthermore, predicted flow model error estimates are verified with one specific measurement series. The results confirm the approach and show that model errors vary significantly within the operational envelope dependent on the actual flow conditions. Finally the obtained flow model parameter distributions can be applied as part of a standard workflow to provide an uncertainty analysis of a flow assurance system comprising both design parameters and inherent flow model errors in one step. © BHR Group 2013. Source

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