Numerical calculations were conducted to simulate the flow and mass transfer in narrow membrane channels equipped with delta winglets,which are often used as longitudinal vortex generators to enhance heat transfer in heat exchanger applications.The channel consists of an impermeable solid wall and a membrane.The delta winglets are attached to the solid wall surface to enhance the mass transfer near the membrane surface and suppress the concentration polarization.The winglet performance was evaluated in terms of concentration polarization factor versus consumed pumping power.Calculations were implemented for NaCl solution flow in a membrane channel having a height of 2.0 mm for Reynolds numbers ranging from 400 to 1000.The delta winglets were optimized under equal pumping power condition,and the results of optimization suggest winglet height of 5/6 of the channel height,aspect ratio of 2.0,attack angle of 30°,and a winglet interval equal to the channel height.The optimal delta winglets were compared with the optimal rectangular winglets we found previously,and it is shown that the rectangular winglets yield a somewhat better performance than the delta winglets.
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