Numerical Investigation of Bubble Movement in Magnetic Nanofluids

Abstract

In this study, the idea to generate electrical energy by using waste heat is suggested. In this idea, the electrical energy can be generated by a magnetic nanofluid and bubble movement. Thus, bubble movement in a magnetic fluid is numerically investigated using the commercial CFD package COMSOL Multiphysics for effective energy generation. The slug characteristics are also investigated because it can be generated by merging each bubble. The level-set method and phase-field method are used to simulate the bubble and slug movement, respectively. For the investigation, EFH1 and EFH3 are selected as working fluids; they are commercial magnetic fluids manufactured by Ferrotec, and each fluid contains different amounts of magnetic particles. The solvers are validated by comparing the numerical results with previous research studies and experimental data for reliable results. The properties of a fluid can be changed by solid particles if the particles are dispersed in the fluid. These particles can affect the bubble and slug characteristics, such as shape, velocity and wake. Thus, the effect of solid particles is first studied by observing the bubble and slug movement in each magnetic fluid. In the slug investigation, the effects of some parameters are also studied, such as slug length and liquid backflow. The patterns of bubble and slug movement are investigated to predict the effective condition for the energy generation. The effective bubble and slug movements are predicted by evaluating the disturbance of the surrounding magnetic fluid for each flow pattern. A magnetic force can be created, and it can affect any phenomena when the magnetic field is applied to the system. Thus, the effect of the magnetic force is also investigated because the magnetic field should be applied to the system for the electrical energy generation. Finally, the important factor for energy generation is identified by comparing the results.