Due to a cancellation by one of our speakers, there will be no material series seminar this week and so no seminar at the University of Ottawa.
However! Two of our very own grads, Yannick Cormier and Philippe Dupuis will be presenting their work at Carleton University this Friday. So come out to support your fellow grad students and see what Carleton has to offer.
Date: Friday 22nd March, 2013
Where: Mackenzie Building ME3124 (Carleton University)
The abstracts of the talks are below. For those of you deterred by the logistics of getting to Carleton – there is a free shuttle bus that runs between the two campuses. See the shuttle timetable. The Carleton shuttle bus-stop is not far from the Mackenzie building.
The background to the talks and abstracts are below.
Energy efficiency has become a growing concern in a world driven by a fossil fuel economy. To this end, increasing the performance and decreasing cost, weight and volume of gas turbines has become a critical research focus. Heat exchangers such as recuperators and intercoolers help improve the efficiency of gas turbines by recovering the waste heat generated by this process. Compact heat exchangers with unit cells using wire mesh as the internal heat transfer surface have been developed at Brayton Energy Canada, but several difficulties are encountered with conventional joining techniques.
Cold Spray was successfully used to deposit an outer layer and the current study focuses on the viability of depositing fins on this outer layer. Due to process restrictions, the pressure drop across the fin array needs to be minimal, while maintaining a very high heat transfer rate per unit area.
Production of Pyramidal Fin Arrays using Cold Gas Dynamic Spraying
This work studies the manufacturability of pyramidal fin arrays produced using the cold spray process. Near‐net shaped pyramidal fin arrays of various sizes and fin densities were manufactured using commercially available steel wire mesh. Cold Spray parameters were determined to obtain near net shape fins. Different types of materials for the fins were successfully deposited on the compact heat exchangers, such as aluminum and stainless steel. Feedstock powders and their grains were characterized for morphology. Clogging of the wire mesh was investigated with a 30 wire per inch mask. A range of standoff distances between the different components of the system was empirically determined. Fin array characterization was performed to assess porosity levels and fin geometry.
Performance of Pyramidal Fin Arrays
This work studies the heat transfer and fluid mechanics performance of pyramidal fin arrays produced using the cold spray process. Empirical correlations were determined between the Reynolds number and friction factor for these shapes of fins. Also, correlations between the Reynolds number and the convective heat transfer coefficient were obtained. These relations were used in a numerical model in order to determine the most appropriate fin array geometry, depending on target specifications, fluid input conditions and spatial constraints. Results obtained correlate with data published for banks of tubes with similar dimensionless pitch. A characteristic change in the performance slope at a critical Reynolds number is observed. The fins produced using the cold spray process outperform traditional straight‐cut fins at the same fin density due to increased fluid mixing and turbulence caused by the discontinuity of these features.