温度对正向渗透的影响机制与数值模拟

正向渗透(FO)是一种以溶液自身渗透压作为推动力的膜分离技术。温度对溶液、膜的性质以及溶液与膜之间的相互作用有很大影响,进而影响FO的水通量。利用数值模拟与试验研究了温度对FO性能的影响。结果表明,当膜两侧等温时,FO水通量随着温度的升高而增大;当膜两侧不等温时,原液(FS)一侧温度的影响比提取液(DS)一侧更大,主要是因为温度升高降低了溶液黏度,强化了过膜扩散过程,而温度对DS渗透压的影响不明显。在不同温度条件下,FO水通量和热通量随流量的增大而增大,主要是由于流速的增大压缩膜表面的流体边界层,强化了传质和传热过程。

Effect of temperature on forward osmosis and its numerical simulation

Forward osmosis(FO)is a new membrane technology with the osmotic pressure of solution as the driving force.The water flux in FO process depends heavily on the temperature due to its effects on properties of solution and membrane and the interaction between them.In this study,the effect of temperature in FO process was investigated using numerical simulation and experiments.The results show that the FO water flux increases with temperature.In the presence of transmembrane temperature difference,the temperature of feed solution predominates the water flux over the temperature of draw solution,due to decreased solution viscosity and enhanced diffusion with elevated temperature.At different temperature profiles,water and heat flux increase with flow rate,resulted from the enhancement of mass and heat transfer within the depressed fluid boundary layer on the membrane surface.