Large eddy simulation of particle deposition in fully developed turbulent fin-tube heat exchanger

Abstract

Large Eddy Simulations are performed to investigate particle deposition within a fin-tube heat exchanger operating in fouling conditions for waste heat recovery. The particle equation of motion is solved using Lagrangian Particle Tracking method taking into account both drag and lift forces. The particle diameters considered range from 1 to 24 µm, corresponding to dimensionless particle relaxation times (${\tau }_p^{+}$) between 0,18 and 106,24. A Critical Deposition Velocity Model (CDVM) is integrated to simulate the fouling in the fin-tube geometry and is compared to the conventional Trap Wall Model (TWM) where the particle deposits when it hits the wall. In the framework of particle-laden regular channel flows, both models lead to a good agreement on the evolution of $V_d^{+}$ as function of the dimensionless particle relaxation time (${\tau }_p^{+}$). For the fin-tube geometry, it is found that the effect of gravity is negligible on the deposition velocity whereas the deposition model has a considerable influence on particle deposition and dispersion. Results show that particles size and turbulence fluctuations are the driving parameters of particle dispersion and deposition trends. Moreover, analysis of means of local distribution of particle dispersion and local deposition on fin-tube walls depict four newly identified fouling regimes as a function of the dimensionless particle relaxation time (τp+).