This article presents numerical simulations of conjugated heat transfer in a fouled channel with a moving depositing front. The depositing front separating the fluid and the deposit layer is captured using the level-set method.
Performance of UV reactors for water disinfection is investigated in this paper. Both experimental and numerical studies are performed on base reactor LP24. Enterobacteria phage MS2 is chosen as the challenge microorganism in the experiments. Experiments are conducted to evaluate the effect of different parameters, i.e. flow rate and UV transmission, on the reactor performance. Simulation is carried out based on the commercial software ANSYS FLUENT with user defined functions (UDFs) implemented. The UDF is programmed to calculate UV dose absorbed by different microorganisms along their flow trajectories. The effect with boundary layer mesh and without boundary layer mesh for LP24 is studied. The results show that the inclusion of boundary layer mesh does not have much effect on the reactor performance in terms of reduction equivalent dose (RED). The numerical results agree well with the experimental measurements, hence validating the numerical model. With this achieved, the numerical model is applied to study other scaled reactors: LP12, LP40, LP60 and LP80. Comparisons show that LP40 has the highest RED and log inactivation among all the reactors while LP80 has the lowest RED and log inactivation.
Laminar three-fluid stratified flow which involves two different moving interfaces is numerically investigated in a two-dimensional domain in this paper. These interfaces are captured using the level-set method via two level-set functions. The effects of various parameters including Froude number Fr and Weber number We as well as the initial locations of the two interfaces on the evolution of the two interfaces are investigated. It is found that the decrease of We number increases the entry length. For a given volumetric flow rate ratio, the interfacial location at fully developed flow is identical irrespective of the Froude and Weber numbers as well as the initial interfacial location at the inlet. The interfacial locations for fully developed flow show distinct behaviors under different flow rate ratios and viscosity ratios. Increase of volumetric flow rate and viscosity for any one of the fluids increases the pressure drop in the channel. The study of pressure gradient reduction factor (PGRF) shows that it is possible to achieve pressure gradient reduction by introducing less viscous fluids in the transportation of a more viscous fluid.
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