Development of a compact 500 W direct methanol fuel cell stack

A 71-cell direct methanol fuel cell (DMFC) stack has been developed at Forschungszentrum Julich. The system consists of the stack, a water/methanol tank, a heat exchanger, a pump and compressors as auxiliary components. The auxiliary components are driven by the DMFC stack itself without external power sources. The DMFC stack consists of 71 cells with an area of 144 cm(2). The current collectors are manufactured of stainless steel (1.4571) with a cell pitch (distance between two membrane electrode assemblies (MEAs)) of only 2 mm. The MEAs are fabricated in-house by a combination of a decal and direct coating method. The thickness of each current collector is 0.3 mm. Each cell is provided with effective flow fields for a homogeneous flow distribution, The flow distribution has been calculated and approved by experiments. Therefore, the necessary stoichiometric air flow rate is only in the range of 2-3. The air compressor is designed to supply air with a maximum pressure of 1.5 bar absolute to the cell. (C) 2002 Elsevier Science B.V. All rights reserved

Novel method for investigation of two-phase flow in liquid feed direct methanol fuel cells using an aqueous H2O/O2 solution

One major issue in the development of direct methanol fuel cells (DMFC) is the management of the evolving CO2 gas bubbles in the flow fields. These bubbles influence the flow distribution and therefore the power density of a cell. In this paper, a novel method for in situ production of bubbles in a test cell made of perspex is presented. The method is based on the decomposition of hydrogen peroxide solution (H2O2) to oxygen and water in aqueous media at the presence of a catalyst. By using an appropriate H2O2-concentration, the gas evolution rate can be set to same order of magnitude as in real direct methanol fuel cells. This approach allows the simulation of the flow distribution in DMFC by simple low-cost hardware. As no current conducting parts are needed, the whole dummy cell can be made of perspex to ensure a complete visibility of the flow.In a perspex flow cell with an active area of 600 cm(2) the flow homogeneity as a function of gas evolution rate, flow field and manifold design was investigated. Experiments show that splayed manifolds have a superior performance concerning flow uniformity compared to other designs. The use of grid structures as a flow field gives good bubble transport at all investigated current densities. (C) 2003 Elsevier B.V. All rights reserved

Materials in the field: object-trajectories and object-positions in the field of contemporary art

The paper explores the centrality of the physical art object in the field of contemporary art with reference to their material specificities. It is based on an ethnographic study of the conservation laboratory at the Museum of Modern Art (MoMA) in New York and draws from three detailed case-studies where the temporal and spatial trajectory of art objects led to changes in the processes of collaboration, competition, and repositioning of those agents involved in production, exhibition and conservation. The study demonstrates the importance of artworks qua physical objects in the field of contemporary art, claiming attention to materiality in field theory and developing an object-orientation methodology in field analysis. Artworks are shown to intervene in field processes both reproducing divisions and re-drawing boundaries within and between fields, actualizing positions of individuals and institutions