“…A constant thermophoretic coefficient K th z 0.55 has been concluded to be applicable for the particles in transition regime K n z 1 and free molecule flow regime K n [ 1, which represents that the thermophoresis in the regions is independent of thermal conductivity ratio and has its largest effect [33]. It has been obtained that, when the particle size involved falls in the continuum regime K n ( 1.0, the effect of thermophoresis is significantly enhanced with reduced heat conductivity in particles because the thermophoretic coefficient K th decreases continuously with increasing particle sizes [34]. This has been explained by considering that the thermophoretic mechanism for larger particles is subjected to the gas slipping along the nonuniformly heated particle surface, where the nonuniformity is stipulated by the temperature gradient of gas and strongly depends on the thermal conductivity of particles [35].…”