Numerical investigation on thermophoretic deposition of particles in turbulent duct flow with conjugate heat transfer: Analysis of influencing factors

Abstract

Thermophoretic deposition of particles in turbulent duct flow is of significant relevance in energy and thermal engineering applications. However, conjugate heat transfer (CHT) was commonly not considered in the previous studies, but may have crucial influences on particle deposition behaviors. Therefore, thermophoretic particle deposition in turbulent duct flow with and without CHT was numerically investigated by using $$\overline {v{\prime ^{_2}}} - f$$ turbulence model and discrete particle model (DPM) with a modified discrete random walk method. After grid independence study and numerical verification, several important influencing factors on particle deposition velocity were studied, such as flow Reynolds number, temperature difference between inlet hot air and cool wall, thermal conductivity ratio and width ratio of solid and fluid domain. The thermophoresis greatly increases deposition velocity of small particles but has no influence on large particles. The critical particle relaxation time $$\tau _{\rm{p}}^ + $$ for thermophoresis effect is 20, which is the same for all the cases in this study. The corresponding particle diameter is 28 µm. The thermophoretic deposition is enhanced when the flow Reynolds number and temperature difference between air and wall increase. This is because the wall-normal temperature variety is higher for large Reynolds number and temperature difference, which can enhance thermophoretic deposition. However, CHT reduces the thermophoretic deposition by decreasing temperature difference in fluid region. Besides, higher thermal conductivity ratio and width ratio of solid and fluid domain will decrease the thermophoretic deposition, as thermal conduction in solid domain becomes more intense.