Effect of entrance condition on frictional losses and transition to turbulence in minichannel flows
Abstract
In studying the fluid flow and heat transfer in
microchannels and minichannels, various claims have been
made regarding transition at Reynolds numbers significantly
below 2300. As a first step in identifying the reasons for
such reports on early transition, the effect of entrance
geometry on the pressure drop and transition to turbulence
was studied in a conventional channel of 19 mm inside
diameter (Kandlikar and Campbell [1]). As a second step,
the effect of entrance condition on pressure drop and
transition to turbulence is studied in small channels with
diameters of 1.067 mm and 0.457 mm. The two entrance
conditions employed for both channels are re-entrant and
smooth. The experimental results show the effect of
entrance condition on local friction factor, transition
Reynolds number, and Hagenbach’s factor.
Keywords: entrance length, pipe flow, transition,
laminar, turbulent, minichannel.
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