Abstract
In this study, the deposition of solid particles in natural convection flow in a square cavity (heat exchanger) filled with air is investigated numerically using an Eulerian–Lagrangian hybrid method. Walls of the enclosure are insulated and several pairs of heater and cooler (HACs) with isothermal walls of Th and Tc (Th>Tc) are placed inside the cavity. An Eulerian (finite volume) approach is used to solve the flow mass, momentum and energy conservation (in a two-dimensional domain) for the ambient continuum. A Lagrangian method is then used to track about 6000 discrete particles, randomly distributed within the domain (i.e., the enclosure). Effects of the drag, lift, gravity, buoyancy, pressure gradient, shear stress terms, thermophoresis and Brownian forces on particles movements are addressed. Furthermore, effects of various design parameters on the heat transfer rate and deposition of particles such as Rayleigh number (104≤Ra≤107), number of the cooler and segmentation of the heater and cooler (HAC) are investigated. The simulations show that the thermophoretic force can significantly affect the distribution of nanoparticles at lower Rayleigh numbers. It is also found that at lower Rayleigh numbers the particle distribution is strongly non-uniform. Moreover, the results of this study showed by increasing the number of coolers and splitting HAC into smaller segments, the deposition rate of the solid particles and heat transfer rate changes significantly.
Published Version
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