NUMERICAL STUDY OF TWO IMMISCIBLE LIQUIDS MIXING IN A SPINNING DISC REACTOR

Abstract

A numerical study of mixing two immiscible liquids in the spinning disc reactor (SDR) is performed with a commercial CFD software, ANSYS Fluent 15.0.7. Many advantages of the SDR over conventional reactors were reported in literatures. For the simulation of the mixing flow inside this reactor. General conservation equations and VOF method are taken into account and discretized by a finite volume method. The QUICK and Compressive schemes are used for interpolation of interfacial variables. The SDR studied in this work has two inlets at the top which feed different immiscible liquids. Water and n-heptane were selected for the computation of interfacial area between phases and its mean residence time in the reactor, which lead to mixing and product yielding performance. The rotating speeds of 10 to 2500 rpm and the liquid flow rate of 5.330 to 15.708 mL/s each are varied. After all cases were computed, the appropriate range of rotating speed is found to be 50 to 250 rpm. Beyond the range, the liquid film inside the SDR faces the instability of film itself. The range of the computed interfacial area and the residence time are between 4.97×10-3 to 6.35×10-2 m2 and 0.5 to 3.4 seconds, respectively. The interfacial area is found to increase with the liquid flow rate but not the rotating speed. The residence times of water and n-heptane decrease when the flow rate or rotating speed increases. Moreover, the high rotating speed seems to have an ability to maintain the uniform distribution of the liquid film. Adding two more liquid inlets or equally shifting inlets from the center reduces the interfacial area. However, arranging the inlets asymmetrically has a potential to increase the interfacial area. Therefore, there are still having various choices of design to be discovered, such as feeding inlet configuration, disc surface roughness and stationary casing, for the improvement of the reactor performance in the future.