Advanced Microfluidics Team

P. A. García-Salaberri, M. Vera, R. Zaera, Int. J. Hydrogen Energy 36 (2011) 11856–11870. (left) Nonlinear Toray carbon paper TGP-H-060/090 mechanical behavior in the through-plane direction calculated by numerical derivation of the true stress/strain curve obtained from the data reported by different authors. (right) Porosity field, GDL intrusion into the channel, and compression stress at the rib symmetry plane obtained for different imposed rib displacements (expressed both in mm and as a percentage of the initial GDL thickness of 190 um) and for an initial porosity of 0.8.

P. A. García-Salaberri, D. García-Sánchez, P. Boillat, M. Vera, K. A. Friedrich, Hydration-dehydration cycles in PEFCs operated with wet anode and dry cathode feed: A neutron imaging and modeling study, Under review. (left) From top to bottom: computed distributions of liquid saturation in the anode channel, and relative humidity in the anode and cathode channels, corresponding to the low- and high-performance states of the hydration-dehydration cycles. The 2D-distributions were obtained by averaging the computed 3D fields in the through-plane direction (z-coordinate) at every point (x,y). The average value of the distributions is indicated at the top of each subplot. (right) From top to bottom: computed distributions of current density, membrane ionic resistance, and membrane temperature, corresponding to the low- and high-performance states.

D. García-Sanchez, T. Ruiu, K. A. Friedrich, J. Sánchez-Monreal, M. Vera, J. Electrochem. Soc. 163 (2016) F150–F159. Estimation of the global balance of water (BOW) in g/h at (a) 60ºC and (b) 80ºC. The reference conditions (50% RH at both anode and cathode) are indicated by a white cross. Color scale represents a qualitative behavior of the cell. Blue is used for high performances at stable condition, purple for flooding behavior, green for slight loose of performances with stable behavior and yellow for unstable behavior with deactivation. As shown, BOW at 60ºC is always positive and the cell behavior remains always stable. In contrast, at 80ºC BOW is negative for low cathode RH conditions which evidences unstable cell performances. Negative BOW levels have been substituted by lines that indicate the relative humidity of the outlet streams that gives zero BOW.

P. A. García-Salaberri, M. Vera, Energy 113 (2016) 1265–1287. (left) Schematic of the computational domains covered by the 2D anode and cathode GDL models and the local 1D model (MPLs, PEM, and CLs), showing the x-y coordinate system, cell temperature, methanol and oxygen concentrations at the GDL/Channel interface, anode and cathode channel saturation levels, and the notation used for the geometrical parameters. The inset shows the electrochemical reactions modeled at the anode and cathode catalyst layers. (right) Schematic of the 3D/1D MEA + 1D channel liquid-feed DMFC model. 1D models for the anode and cathode channels are coupled to the 3D/1D MEA model at each downstream station to account for the downstream variation of the different flow variables.

P. A. García-Salaberri, M. Vera, I. Iglesias, J. Power Sources 246 (2014) 239–252. Computed gas-void fraction distributions for different gas coverage factors at the GDL/Channel interface.

P. A. García-Salaberri, M. Vera, J. Power Sources 285 (2015) 543–558. Computed cell performance at various GDL compression ratios, CR, for the serpentine flow field of stainless steel (metallic): (a) cell voltage, (b) power density, (c) parasitic current density, and (d) fuel utilization, as a function of cell current density. Reference markers are plotted at intervals of 50 mV.

P. A. García-Salaberri, M. Vera, Energy 113 (2016) 1265–1287. Computed cell performance as a function of methanol concentration at the GDL/channel interface and cell temperature: (a) and (b) output power density and parasitic current density, and (c) polarization curves corresponding to two specific methanol concentrations and various cell temperatures. The oxygen concentration is equal to 6 mol/m3.

J. Sánchez-Monreal, P. A. García-Salaberri, M. Vera, ECS Trans. 72 (2016) 1-16. Schematic representation of the physical domains covered by the 1D across- and 1D along-the-channel models, showing the inlet conditions, the channel/rib dimensions, and the thickness of the different layers of the MEA. Left: side view, right: cross-sectional view.

J. Sánchez-Monreal, P. A. García-Salaberri, M. Vera, ECS Trans. 72 (2016) 1-16. Anode overpotential measured experimentally by previous authors and computed by the present model. Operating conditions: 1M ethanol feed concentration, 70ºC.

P. A. García-Salaberri, G. Hwang, M. Vera, A. Z. Weber, J. T. Gostick, Int. J. Heat Mass Transf. 86 (2015) 319–333. (a) Computational domain used for effective gas diffusivity calculations with the LBM, showing the different elements of the system. (b) and (c) Computed concentration fields corresponding to simulations in the in- and through-plane directions, respectively. The resolution of the 1.3x1.3x0.28 mm 10% PTFE-treated GDL domain was downscaled by a factor 3x3x1 to avoid memory limitations of the 48 GB rendering workstation.

P. A. García-Salaberri, J. T. Gostick, G. Hwang, A. Z. Weber, M. Vera, J. Power Sources 296 (2015) 440–453. (a) Schematic of the methodology used to compute functional relationships for the local dry and relative effective diffusivities on local porosity and local saturation, respectively. LB simulations were performed on XCT images of arbitrarily selected subdomains that are representative of the GDL microstructure, and have nearly uniform porosity and saturation distributions. The rendered image stack corresponds to the breakthrough point. The direction of water injection in the invasion experiments is indicated. (b) and (c) Representative elementary volume (REV) determinations of (b) porosity, and (c) water saturation at the breakthrough point for Toray TGP-H-120 carbon paper. The y-axis shows the range of values calculated inside randomly drawn boxes of different thickness as indicated on the x-axis; the length in the material plane is kept equal to 0.4 mm. For the analysis of the porosity the outer high-porosity surface regions of the GDL were included, while for the water saturation only the core region was considered. The unrepresentative microscopic scale (highly influenced by the granularity of the material) and the representative macroscopic scale (leading to consistent functional relationships for the effective diffusivity) are clearly identified in (b).

P. A. García-Salaberri, J. T. Gostick, G. Hwang, A. Z. Weber, M. Vera, J. Power Sources 296 (2015) 440–453. (left) Computed local relative effective diffusivity for (a) the through-plane (TP), and (c) the in-plane (IP) direction, as a function of local average saturation. The results are marked with hollow symbols according to the thickness of the subdomains in the LB simulations, including the best fit to a power law. (right) Distribution of the power-law exponent, associated to each data point presented on the left panel for (b) the TP, and (d) the IP direction.

P. A. García-Salaberri, D. García-Sánchez, P. Boillat, M. Vera, K. A. Friedrich, Hydration-dehydration cycles in PEFCs operated with wet anode and dry cathode feed: A neutron imaging and modeling study, Under review. (a) Variation of the average current density and high-frequency resistance as a function of time, after a change of the cathode stream from fully-humidified to non-humidified conditions, while keeping the anode stream fully humidified. (b) Distributions of liquid water thickness from through-plane neutron imaging experiments (top view) at different times during a hydration-dehydration cycle. The active area of the cell and the anode inlet chamber are indicated by red dashed lines; the cathode inlet is located at the diametrically opposite corner. Membrane material: Nafion 111. The subfigure in the frame shows the current density distributions during a hydration-dehydration cycle previously obtained in a segmented cell by Sánchez et al. (J. Electroanal. Chem. 649 (2010) 219-231).

D. García-Sanchez, T. Ruiu, K. A. Friedrich, J. Sánchez-Monreal, M. Vera, J. Electrochem. Soc. 163 (2016) F150–F159. Relation between RH and cell performance stability. Squares represent the combination of RH conditions at anode and cathode adopted during the different experiments. Purple is used for flooding behavior, blue for high performances at stable condition, green for slight loss of performances with stable behavior, and orange for unstable behavior with deactivation.

Polarization curves corresponding to different methanol feed concentrations. Other operating conditions: 80 ºC cell temperature, 5 cl/min anode flow rate, and 2 l/min cathode flow rate.

Pablo and Marc Secanell attending a plenary lecture.

Pablo and Marc Secanell attending a plenary lecture.

Coffee break. From left to right: Marc Secanell, Jordi Pons-Prats and Pablo.

Welcome cocktail. From left to right: Jeff Gostick, Pablo García-Salaberri, and Juan Sánchez-Monreal.

Leaving the congress. From left to right: Marcos Vera, Juan Sánchez-Monreal, and Pablo García-Salaberri.