- 學位論文
真空式與直接接觸式薄膜蒸餾於海水淡化之滲透通量模擬
Modeling on the distillate fluxes of DCMD and VMD in desalination
摘要
本研究之目的為模擬計算直接接觸式薄膜蒸餾與真空式薄膜蒸餾於海水淡化之滲透通量，並比較其性能差異，透過改變不同的操作參數(進料流量、溫度、濃度)來探討各參數對於濾速之影響，以此做進一步討論最適化操作下之操作條件。 結果顯示本研究結合各項海水物性變數並由Dusty-Gas model模擬之滲透通量相當吻合實驗值。溫度極化效應對MD系統影響甚鉅，而VMD系統雖然其極化現象較易獲得改善而有效提高滲透通量，但在VMD系統會因滲透通量的上升而增加其操作成本。成本評估成果顯示，DCMD系統比VMD系統較適合達到經濟規模的設置。 在DCMD，增大物料流率可降低溫度極化及濃度極化現象，其中增大進料側流率會提高熱使用效率，但濾液側流率增大會因透膜熱傳導量增加而降低熱使用效率。
並列摘要
The objectives of this study included the flux estimation of DCMD and VMD in seawater desalination and their comparisons, and aimed to investigate the optimal operating conditions for seawater desalination. The operating parameters in the simulation included the feed flow rate, temperature and concentration. The simulation results based on considering the combination of Dusty-Gas model with the seawater properties agree very well with the experimental data. The results also show that the temperature polarization has a significant influence on the flux. The polarization phenomena in the VMD system can be easier improved to increase the distillate flux. However, the operating cost of VMD increases with the increase of distillate flux. The cost evaluation shows that the DCMD system is more economic than the VMD system. Both the temperature and concentration phenomena can be reduced by increasing the flow rates in the DCMD system. It is noted that increasing the feed side flow rate also enhances the thermal efficiency, while increasing the flow rate in distillate side will raise the heat conduction through the membrane and result in lowering the thermal efficiency.