Kanagaraj, Dheepan Chakravarthii Musiri
(2019)
Parametric Study Of Microchannel Substrates For High Power Led Applications.
PhD thesis, Universiti Sains Malaysia.
Abstract
In this study, microchannel substrates with non-uniform cross-sections were investigated for thermal management in LEDs. Extensive characterizations were done numerically and experimentally for high power LED applications to employ the novel substrates with channels. From the comprehensive literature review, converging-diverging and diverging-converging channels were focussed for this research due to certain advantages such as efficient secondary flow formation and mitigation of nucleation boiling. A detailed and constructive parametric study was conducted by CFD simulations to identify the thermal performance of substrates based on different geometrical parameters such as channel length, converge-diverge angles, hydraulic diameters (Dh) and aspect ratio (γ). Ideal secondary flow formation in CD20 and DC90 microchannels contributed for enhanced heat transfer performance. From the numerical results, the substrates with higher thermal performance were CD20 (L1=9mm, Dh=512μm, Wmax=3mm) and DC90 (L1=3.25mm, Dh=651μm, Wmax=3mm). The CD and DC channelled substrates were manufactured by micro milling process and the surface roughness were measured using AFM. A high-power LED was mounted on different CD and DC substrates and thermal transient characterizations were done using Thermal Transient Tester (T3Ster©). The critical thermal parameters such as thermal resistance and junction temperature were calculated from the structure functions and smoothed response curves. The influence of input current and ambient temperature on CD and DC substrates were elaborated to affirm the consistency in the thermal performance irrespective of its operating conditions.
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