s8.3 Diffusion and mass transfer , o/(扩散和单 within single phase 向传质) 8.3.1 Molecular diffusion in binary mixtures Diffusion (P Features a hatsdiffusioni3 Diffusion is the movement, under the infiuence of a physical stimulus(物理驱动)oam individual component(单独的组份 through a mixture
一.Diffusion（P511） Features: 1. ～ What’s diffusion ？ Diffusion is the movement, under the influence of a physical stimulus（物理驱动）, of an individual component（单独的组份） through a mixture. 8.3.1 Molecular diffusion in binary mixtures （扩散和单 向传质） §8.3 Diffusion and mass transfer within single phase
s8.3 Diffusion and mass transfer , o/(扩散和单 within single phase 向传质) 8.3.1 Molecular diffusion in binary mixtures Diffusion (pu 2 Why reason? The most cause of diffusion is a concentration gradient of the diffusing component. 3. Purpose? A concentration gradient(浓度梯度) tends to move the component in such a direction as to equalize concentration and destroy the gradient
一.Diffusion（P511） 2. ～ Why reason? The most cause of diffusion is a concentration gradient of the diffusing component. 3. ～ Purpose? A concentration gradient（浓度梯度） tends to move the component in such a direction as to equalize concentration and destroy the gradient. 8.3.1 Molecular diffusion in binary mixtures （扩散和单 向传质） §8.3 Diffusion and mass transfer within single phase
8.3.1 Molecular diffusion in binary mixtures Diffusion (Pai) 4 ≈ Steady- state flux When the gradient is maintained by constantly supplying the diffusing component to the high- concentration end of the gradient and removing it at the low-concentration end. there is a steady-state flux of the diffusing component This is characteristic of many mass-transfer operations
一.Diffusion（P511） 4. ～ Steady-state flux When the gradient is maintained by constantly supplying the diffusing component to the highconcentration end of the gradient and removing it at the low-concentration end, there is a steady-state flux of the diffusing component. This is characteristic of many mass-transfer operations. 8.3.1 Molecular diffusion in binary mixtures
83.I Molecular diffusion in binary mixtures 5 Although the usual cause of diffusion is a concentration gradient, diffusion can also be aals ed by an activity gradient(能动梯度) as in reverse osmosis(反渗透),bya pressure gradient, by a temperature gradient, or by the application of an external force field (外场力), as in a centrifuge(离心力场)
5. ～ Other reasons Although the usual cause of diffusion is a concentration gradient, diffusion can also be caused by an activity gradient（能动梯度）, as in reverse osmosis（反渗透）, by a pressure gradient, by a temperature gradient, or by the application of an external force field （外场力）, as in a centrifuge（离心力场）. 8.3.1 Molecular diffusion in binary mixtures
8.3.1 Molecular diffusion in binary mixtures 6.< What's thermal diffusion?热扩散 Molecular diffusion induced by temperature gradient is thermal diffusion. 7。 What's the force diffusion?强制扩散 Molecular diffusion induced by the application of a force from an external filed is forced diffusion
6. What’s thermal diffusion?热扩散 Molecular diffusion induced by temperature gradient is thermal diffusion. 7. What’s the force diffusion? 强制扩散 Molecular diffusion induced by the application of a force from an external filed is forced diffusion. 8.3.1 Molecular diffusion in binary mixtures