Numerical calculations were conducted to simulate the flow and mass transfer in narrow membrane channels with and without flow disturbers. The channel consists of an impermeable solid wall and a membrane surface with ...Numerical calculations were conducted to simulate the flow and mass transfer in narrow membrane channels with and without flow disturbers. The channel consists of an impermeable solid wall and a membrane surface with a spacing of 2.0 mm. The flow disturbers studied include rectangular winglets, which are often used as longitudinal vortex generators to enhance heat transfer in heat exchanger applications, as well as square prism, triangular prism, and circular cylinder, which are used here to mimic the traditional spacer filaments for comparison of their abilities in enhancing the convective mass transfer near the membrane surface to alleviate the concentration polarization. The disturber performance was evaluated in terms of concentration polarization factor versus consumed pumping power, with a larger factor meaning a more serious concentration polarization.Calculations were carried out for Na Cl solution flow with Reynolds numbers ranging from 400 to 1000. The results show that the traditional flow disturbers can considerably reduce the concentration polarization but cause a substantial pressure drop, while the rectangular winglets can effectively reduce the concentration polarization with a much less pressure drop penalty. The rectangular winglets were optimized in geometry under equal pumping power condition.展开更多
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 ...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.展开更多
基金Supported by Tsinghua University Initiative Scientific Research Program(20131089319)
文摘Numerical calculations were conducted to simulate the flow and mass transfer in narrow membrane channels with and without flow disturbers. The channel consists of an impermeable solid wall and a membrane surface with a spacing of 2.0 mm. The flow disturbers studied include rectangular winglets, which are often used as longitudinal vortex generators to enhance heat transfer in heat exchanger applications, as well as square prism, triangular prism, and circular cylinder, which are used here to mimic the traditional spacer filaments for comparison of their abilities in enhancing the convective mass transfer near the membrane surface to alleviate the concentration polarization. The disturber performance was evaluated in terms of concentration polarization factor versus consumed pumping power, with a larger factor meaning a more serious concentration polarization.Calculations were carried out for Na Cl solution flow with Reynolds numbers ranging from 400 to 1000. The results show that the traditional flow disturbers can considerably reduce the concentration polarization but cause a substantial pressure drop, while the rectangular winglets can effectively reduce the concentration polarization with a much less pressure drop penalty. The rectangular winglets were optimized in geometry under equal pumping power condition.
基金Supported by Tsinghua University Initiative Scientific Research Program(20131089319)
文摘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.
