Falling Film Flow Of High Viscosity Fluid On Baffle Plates

High viscosity fluid includes Newtonian fluid and non-Newtonian fluid. The high viscosity will result in flow difficulties. Therefore, non-Newtonian fluid can be considered as Newtonian fluid at low speed.The researches now are most focus on the Newtonian fluid, while research about non-Newtonian fluid is much little. In order to know the flow field and fluctuation when high viscosity flow down along the baffle plates, furthermore to know the mass transfer and heat transfer, a lot of investigation has been done. In this thesis, with water soluble silicone oil, the velocity distribution, film thickness and surface update frequency has been obtained by the experiment and CFD simulation.First, equipment and process of the experiment was designed, and experiment has been carried out to get the instantaneous velocity with the help of Laser Doppler Anemometer. According to the signal represented on the screen, film thickness could be acquired. First,the influence of flow rate and viscosity on the film thickness have been researched and experimental formula has been fit. Then the influence of falling film height and horizontal distance on the film thickness distribution has been researched. Before the experiment of velocity distribution, the change of mean velocity along with time should be acquired to make sure that the mean velocity keeps constant with the time. The velocity distribution along flow direction and horizontal direction were gained at different distance from the plate surface. According to the experiment result, a suitable measurement position has been obtained, where the influence of flow rate and viscosity on velocity distribution along thickness direction has been observed. Compare the experiment result with Nusselt theoretical value, the film thickness and velocity are outnumbered Nusselt value. At last, the surface update frequency has been calculated from the data of the surface velocities.Simulation has been done after the experiment, which has the same boundary condition with the experiment. Compare the mean velocity and film thickness respectively at different flow rates and viscosity on the third baffle plates. The simulation result shows that the shape of velocity distribution along thickness direction is like a parabolic curve. Velocity increases with the flow rate increases and viscosity decreases, while film thickness increases with flow rate and viscosity increase. Total comparison shows that simulation data of film thickness is larger than experimental data while velocity is on the contrary. Furthermore,the simulation data more approach to the experimental data at larger viscosity or flow rate. Both the experiment and simulation result reveal that the baffle plates help the fluid enhance surface update even at low velocity. This is due to the altered direction and the obvious fluctuation on the fluid surface, which is propitious for the mass transfer and heat transfer.