Pressure losses in gas flow through sudden contractive sharp bends in micro channels

Flows through sudden-contractive sharp bends in rectangular cross-section micro channels were studied by using finite volume method. Specifically, the effects of Reynolds number and cross-section area ratio on local flow patterns and bend pressure losses were investigated. Reynolds number ranges from 1 to 200 and the characteristic length is 500 μm. Skin frictions mainly contribute to the pressure losses at low Reynolds numbers while flow separation and vortices dominate the losses at high Reynolds numbers. For low Reynolds numbers, the variation of bend pressure loss coefficient with Reynolds number is similar to the loss of a straight channel with the same center-line length, but the bend loss has a smaller value. The sudden-contractive cross section inhibits the flow separation at high Reynolds number and reduces the pressure loss. The velocity profiles at the cross section of the bend were affected by the contraction. Correlations of pressure loss coefficient as a function of Reynolds number and cross-section area ratio were fitted.