On the optimization of performance in fractal-like branching microchannel heat transfer devices Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/xp68kk75j

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  • Fractal-like branching microchannel flow networks have been found to improve wall temperature uniformity and decrease both pressure drop and flow power compared to arrays of straight microchannels. The present study seeks to maximize the benefits of fractal-like branching channels by means of a gradient-based optimization algorithm. The algorithm identifies the geometric parameters that yield the highest ratio of benefit to cost; the benefit being the heat transfer with cost being flow power. The stream-wise pressure and wall temperature distributions were determined numerically using one-dimensional models validated using experimental diagnostics and computational flow analyses. Pressure distributions were used to assess flow power, and wall temperature was used as an optimization constraint. Several geometric constraints were imposed during optimization to ensure sufficient bonding area for fabrication, to maximize convective surface area and to prevent channel overlap. Three fractal-like devices were studied and optimized: a single-phase heat sink, a two-phase heat sink and a single-phase oil-to-water heat exchanger. The flow rate of the three devices was constrained using a maximum wall temperature constraint for the single-phase heat sink, the critical heat flux for the two-phase heat sink, and a fixed cold side mass flow rate and temperature rise in the case of the heat exchanger. The optimized solutions were found to depend highly on both the geometric and flow constraints imposed. As the terminal channel width was reduced, flow power was reduced in both single-phase and two-phase heat sinks. However, the flow power was increased in the heat exchanger due to the constrained volumetric flow rate. In addition, results show that if a maximum wall temperature constraint is employed, single-phase flow outperforms two-phase flow in terms of reduction in flow power. However when constrained by a critical heat flux, two-phase networks outperform single-phase networks by up to 150%
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  • description.provenance : Approved for entry into archive by Laura Wilson(laura.wilson@oregonstate.edu) on 2011-01-24T23:01:48Z (GMT) No. of bitstreams: 1 HeymannDissertation2010.pdf: 6117658 bytes, checksum: 81c9e69571851af22463dd0cd3a8583b (MD5)
  • description.provenance : Made available in DSpace on 2011-01-24T23:01:48Z (GMT). No. of bitstreams: 1 HeymannDissertation2010.pdf: 6117658 bytes, checksum: 81c9e69571851af22463dd0cd3a8583b (MD5)
  • description.provenance : Submitted by Douglas Heymann (heymannd@onid.orst.edu) on 2011-01-21T19:49:11Z No. of bitstreams: 1 HeymannDissertation2010.pdf: 6117658 bytes, checksum: 81c9e69571851af22463dd0cd3a8583b (MD5)
  • description.provenance : Approved for entry into archive by Julie Kurtz(julie.kurtz@oregonstate.edu) on 2011-01-24T22:10:33Z (GMT) No. of bitstreams: 1 HeymannDissertation2010.pdf: 6117658 bytes, checksum: 81c9e69571851af22463dd0cd3a8583b (MD5)

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