Fluid flow and local heat transfer in a microchannel with single and array of pin fins have been studied. For the single pin fin case, a microchannel with a 150-µm diameter pin fin with a tip clearance was experimentally and numerically studied for three Reynolds numbers in laminar regime. Tip clearances of 0, 30, 45 and 100 µm in a 200-µm high microchannel. Experimental and numerical local temperatures and the corresponding Nusselt numbers along the centerline of the pin fin were presented and discussed. Local temperatures were measured on top of the heater surface and downstream the pin fin through micro resistance temperature detectors (RTDs). A conjugate CFD modeling capable of simulating solid/fluid conduction and convection revealed velocity, heat flux and heat transfer coefficient over the heated surface. Nusselt number and wake length for a range of tip clearances were presented and compared with full-height pin fin. Experimental and numerical results showed that a tip clearance can significantly enhance heat transfer in the wake region. Simulations revealed that tip clearance alters the flow structure by increasing the three dimensionality of the flow, promoting mixing, shortening the wake region, and increasing the velocity downstream the pin fin. A tip clearance with a height of 100 µm was found to provide the best heat transfer enhancement. For a microchannel with array of pin fins with tip clearance, an experimental study carried out with the tip clearance of 0 and 100 µm in a 200-µm high microchannel. Results revealed that introducing tip clearance in pin array can on-average almost double heat transfer coefficient compared to full height (no tip) array of pin fins.
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Doctor of Philosophy (Ph.D.)
College of Engineering and Computer Science
Mechanical and Aerospace Engineering
Length of Campus-only Access
Doctoral Dissertation (Campus-only Access)
Tabkhivayghan, Hanieh, "Tip Clearance Effect on Convective Heat Transfer in Micro Scale Pin Fins" (2020). Electronic Theses and Dissertations, 2020-. 621.