Proton exchange membrane (PEM) fuel cells, with low operating temperatures and high power density, are a reasonable candidate for use in mobile power generation. One large drawback to their use is that their fuel reformer requires not only fuel but also water, thereby requiring two separate reservoirs to be available. PEM fuel cells exhaust enough water in their oxidant stream to potentially meet the needs of the fuel reformer. If this water could be recovered and routed to the fuel reformer it would markedly increase the portability of PEM fuel cells. The goal of this research was to test a previously designed axial flow moisture separator. The separator was employed in a test bed which utilized compressed, heated air mixed with steam to simulate the oxidant exhaust conditions of a 25 kW PEM fuel cell. The simulated exhaust was saturated with water. The mixture was expanded through the turbine side of an automotive turbocharger, which dropped the temperature and pressure of the mixture, causing water to condense, making it available for separation. The humid air mixture was passed over an axial flow centrifugal separator and water was removed from the flow. The separator was tested in a variety of conditions with and without passing chilled water through the separator. The axial separator was tested independently, with a flow straightener preceding it, and with a commercially available centrifugal moisture separator in series following it. It was shown that cooling makes a significant impact on the separation rate while adding a flow straightener does not. Separation efficiencies of 19% on average were experienced without cooling, while efficiencies of 50% were experienced with 3.1 kW of cooling. The separation efficiency of the two moisture separators combined was found to be 31.7% which is 165% that of the axial separator alone under uncooled conditions.

Moisture recovery is important in the operation of many fuel cell systems, especially proton exchange membrane (PEM) fuel cells. The exhaust of a PEM fuel cell is a moderate temperature, pressurized humid air stream. A system that recovers liquid water condensate from the pressurized humid exhaust stream of a PEM fuel cell would markedly increase the effectiveness of such a system. The recovered water could be used to hydrate the fuel cell membrane, and it could supply a hydrocarbon reformer used for generating hydrogen. This project investigated and documented moisture recovery from the simulated humid exhaust stream of a 25 kW fuel cell with an improved axial flow separator. An axial flow centrifugal separator design was chosen as the best candidate due to its high efficiency and low pressure drop and a prototype was designed and constructed. The separator was then integrated into an experimental test system. First, the stream was simulated by heating compressed air and then humidifying it with superheated steam. Then, after expanding through the turbine section of an automotive turbocharger, the humid stream was passed through the moisture separator where liquid water condensate was removed from the flow. Results are presented for varying turbine inlet conditions at three separate separation lengths. It is shown that the separation efficiency for the improved design was 40% higher and the pressure drop was only 1/3 that of the conventional separator.

This project has investigated and formed a basis for the thermal- and flow-induceddynamic loads in the lower parts of a preheater situated in a nuclear power plant.Special attention has been given to the bottom plate that separates the heated andnon-heated secondary steam. Using computational fluid dynamics (CFD), steady RANSsimulations were first used to investigate how the flow into the preheater was affectedby the inlet boundary conditions. From there a steady RANS conjugate heat transfer(CHT) analysis was conducted as to obtain the temperature field within the preheaterand its solid components. This also investigated different approaches in modelling theheat transfer between the primary and secondary steam. Lastly, a scale-resolving LESwas conducted as to obtain the flow-induced dynamic loads on the bottom plate. The results show that the modelling used in previous works gives a less uniformtemperature distribution as compared to when appropriate heat transfer coefficient(HTC) correlations are applied. Regardless of how the heat source is modelled, hot spotswith significantly larger temperatures are present in the bottom plate near the outletsof the bottom tube sections. The root mean square value, amplitude and frequencycontent of the fluctuating force acting on the bottom plate have also been obtained.The results of the analysis provide a good starting point for future work examining ifthe loads on their own or in combination may risk damaging the structure.