The efficiency of heat exchangers is important in the HV ACIR industry. Driven by highenergy standards and increasing competition, manufacturers are seeking to decrease air-sideresistance in heat exchangers by increasing the heat transfer coefficient. Offset strip and louveredfins increase the heat transfer coefficient through two methods -- boundary layer restarting and theinitiation of self-sustained oscillations. The purpose of this thesis is to develop a betterunderstanding of flow and heat transfer in offset strip and louvered fins so that design guidelinesmay be developed. Five geometries are analyzed in this study -- two offset strip and three louveredwith a 25- angle of incidence -- over a Reynolds number range of 100 to 12000. Heat transfer isinferred from mass transfer data acquired using the naphthalene sublimation method, and pressuredrop across each array is detennined using conventional methods. Flow visualization studies areperformed to develop a more complete understanding of the actual flow mechanisms. The resultsshow that vortex shedding in the periodic regime increases heat transfer significantly. Measurementsof local mass transfer along a fin show that local heat transfer behavior on a fin is different for offsetstrip and louvered fins, and these results are used to develop design guidelines Because of the flowstructures at work, short louvered fins may be especially advantageous. Studies of overall behaviorshow that at a given Reynolds number, louvered fins require less area for a given heat duty than dooffset strip fms. However, pumping power is significantly higher for louvered fins. Therefore, ifheat exchanger efficiency is more important than heat exchanger size, offset strip fins may be just asdesirable if not more desirable than louvered fins for certain exchanger geometries and operatingconditions.
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