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In this paper two different types of solid oxide fuel cell (SOFC) geometries are studied via CFD numerical simulations: a) a mono-block-layer build type (MOLB-type) with a porous embedding pipe in the air side of the geometry and a simple planar geometry were modeled feeding biogas obtained from local sludge. The numerical simulations integrated the internal reforming of methane in the anode side and different several phenomena that occur inside of the SOFC such as: mass transfer, heat transfer, species transport, chemical and electrochemical reactions. A detailed comparison of the results such as: current density, species concentration and temperature distributions along the fuel cells is reported. The results showed that the CH 4 , H 2 O, CO, CO 2 concentration and current density distributions had similar trends for both MOLB-type with embedding porous pipe geometry and simple planar geometry. However, higher H 2 concentration and lower average temperature value are obtained from the MOLB-type with embedding porous pipe geometry, which help to handle higher current densities and reduces thermal stress, increasing the performance of the fuel cell. [ABSTRACT FROM AUTHOR]

In this work, a comparison of the thermo-hydraulic performance and the entropy generation rate for two different types of low temperature solar collectors: flat plate solar collector (FPC) and water-in-glass evacuated tube solar collector (ETC), is addressed. The absorber area for both solar collectors were considered to be equal for a reliable comparison. The operation of the solar collectors was simulated under different volumetric flow rates and solar radiation values for the state of Guanajuato in Mexico. The volumetric flow rate for both collectors ranged from 1 to 9 L/min. The variation of the solar radiation was based on: (1) the solar radiation taken from several experimental tests reported elsewhere, (2) the month with the lowest average solar radiation in one year, (3) the average solar radiation of one year and (4) the month with the highest average solar radiation in one year. The buoyancy effects were considered in the CFD simulations using the Boussinesq approximation (BA) model. The distribution profiles of temperature, pressure, and velocity inside the tubes of the solar collectors, along with the local entropy generation rate distribution due to heat transfer and the fluid viscosity, are shown in detail. The results show a better thermal performance for the solar water-in-glass evacuated tube collector (ETC) than for the flat plate solar collector (FPC) at low flow rates (under 3.0 L/min). The outlet temperature reached is similar in both collectors for volumetric flow rates higher than 3.0 L/min. The analysis of the entropy generation rate shows that the generation due to the transfer of heat is higher for the ETC than for the FPC, and this contribution is up to 10% of the total entropy generation rate; on the other hand, the generation rate due to the fluid viscosity is higher for the FPC than the ETC at high volumetric flow rates (above 3.5 L/min), however, this contribution is negligible. Finally, the total entropy generation rate is higher for the FPC than the ETC at low volumetric flow rates (below 3.0 L/min) and this is increased if the solar radiation increases. [ABSTRACT FROM AUTHOR]

Highlights: [•] A MOLB-type SOFC with different biogas compositions is modeled. [•] Internal reforming of methane and water gas shift in the anode side are considered. [•] Changes in the SOFC according to the phenomena inside of them are assessed. [•] A new configuration for the MOLB-type geometry is proposed. [•] Temperature gradients effects in the new configuration are significant. [Copyright &y& Elsevier]