Influence of Alumina Addition to Aluminum Fins for Compact Heat Exchangers Produced by Cold Spray Additive Manufacturing
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Aslan Farjam, Yannick Cormier, Philippe Dupuis, Bertrand Jodoin, and Antoine Corbeil (Submitted March 14, 2015; in revised form July 13, 2015) In this work, aluminum and aluminum-alumina powder mixtures were used to produce pyramidal fin arrays on aluminum substrates using cold spray as an additive manufacturing process. Using aluminumalumina mixtures instead of pure aluminum powder could be seen as a cost-effective measure, preventing nozzle clogging or the need to use expensive polymer nozzles that wear out rapidly during cold spray. The fin geometries that were produced were observed using a 3D digital microscope to determine the flow passages width and fins’ geometric details. Heat transfer and pressure drop tests were carried out using different ranges of appropriate Reynolds numbers for the sought commercial application to compare each fin array and determine the effect of alumina content. It was found that the presence of alumina reduces the fins performance when compared to pure aluminum fins but that they were still outperforming traditional fins. Numerical simulations were performed to model the fin arrays and were used to predict the pressure loss in the fin array and compare these results with experimental values. The numerical model opens up new avenues in predicting different applicable operating conditions and other possible fin shapes using the same fin composition, instead of performing costly and time-consuming experiments.
Keywords
additive manufacturing, aluminum, cold spray, heat transfer, pin fin array
1. Introduction Compact Heat Exchangers (CHE) make up approximately 10% of the total heat exchanger market, and have experienced a yearly growth in sales of 10% compared with 1% growth for other types as a result of the high industrial demand for this category of heat exchangers (Ref 1). CHE have increased heat transfer surface area to volume ratios when compared to more traditional heat exchangers. This is achieved using fins on the mediator wall (or walls) that separates the two flow streams exchanging heat (Ref 2). CHE are ubiquitous in electronics and aerospace applications, where size and weight are important factors. Enormous effort has gone into enhancing the performance of heat exchangers to increase their efficiency. Many factors must be taken into account when trying to optimize a heat exchanger for a specific application including component geometries, heat transfer mechanisms, and flow arrangements (Ref 3).
Aslan Farjam, Yannick Cormier, Philippe Dupuis, and Bertrand Jodoin, Mechanical Engineering Department, University of Ottawa, Ottawa, Canada; and Antoine Corbeil, Brayton Energy Canada, Gatineau, Canada. Contact e-mail: [email protected].
Journal of Thermal Spray Technology
Nomenclature
DPfin DT1 DT2 DTlm g gf go h l q Af Aflow Atot B Cp dh ev FD H h I1 I2 km _ m m Pflow q ReDh
Fin differential pressure (Pa) Inlet temperature difference (K) Outlet temperature difference (K) Log mean temperature difference (K) Fan efficiency Individual fin efficiency Overall fin efficienc
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