4 research outputs found
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Study of a micro-structured PHE for the thermal management of a fuel cell
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.In the constantly growing market of fuel cells, the heat management of the system is a crucial area of research, since it affects the efficiency, operability and lifetime of the fuel cell. The CFD simulations performed for a plate heat exchanger (PHE) with flat plates clearly demonstrate temperature non-uniformity across the membrane of the unit cell. The CFD code was successfully validated with experimental data acquired from a setup that reproduces the geometry and simulates the thermal behaviour of a typical unit PEMFC. Additionally, the performance of a novel PHE, with micro-structured corrugations on its plates, was studied with the previously validated CFD code. The results clearly show that the proposed plate modifications can increase temperature uniformity across the membrane more than 20% compared to that of the flat plate
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Characterization of fluid flow in a microchannel with a flow disturbing step
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The flow around a flow-disturbing step in a rectangular microchannel is studied by measuring the
wall shear rate along the channel, using the electrodiffusion technique and by determining the velocity field
using the -PIV method. A parametric study based on the Design of Experiments (DOE) and the Response
Surface Methodology (RSM) was then performed, and the effect of key design parameters on the flow characteristics
was numerically investigated using CFD simulations. The computational results are in excellent agreement
with the corresponding experimental ones. The CFD simulations cover both the laminar and the turbulent
flow regime. It was revealed that in both flow regimes the step height has a major influence on the recirculation
length. However, the Reynolds number (Re) value affects the recirculation length only in the laminar region,
while the step length seems to have no significant effect compared to the Re and the step height. Finally, new
correlations are proposed predicting the length of the bottom recirculation zone with reasonable accuracy and
can be used as rough guidelines for the design of microdevices