Thermo-Hydrodynamics of Developing Flow in a Rectangular Mini-Channel Array

ABSTRACT

Thermo-hydrodynamic performance of hydrodynamically and thermally developing single-phase flow in an array of rectangular mini-channels has been experimentally investigated. The array consists of fifteen rectangular parallel mini-channels of width 1.1 ± 0.02 mm, depth 0.772 ± 0.005 mm (hydraulic diameter 0.907 mm), inter-channel pitch of 2.0 mm, machined on a copper plate of 8.0 mm thickness and having an overall length of 50 mm. Deionized water used as the working fluid, flows horizontally and the test section is heated directly using a thin mica insulated, surface-mountable, stripe heater (constant heat flux boundary condition). Reynolds number between 200 and 3200 at an inlet pressure of about 1.1 bar, are examined. The laminar-to-turbulent transition is found to occur at Re ≈ 1100 for average channel roughness of 3.3 µm. The experimental pressure-drop under laminar (Re < 1100) and turbulent flow conditions (Re > 1100) closely match with the correlations in literature on developing flow. The experimental Nusselt numbers for both laminar and turbulent flow are found within satisfactory range of values estimated from theoretical correlations existing in the literature on developing flows. Thus, the study reveals that conventional theory, which predicts thermo-hydrodynamics of developing internal flows, is largely applicable for the minichannels used in this study. No new physical phenomenon or effect is observed.

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