Experimental study of particle ($TiO_2$) deposition from hot particle-laden gas (about 1565K) in laminar flow onto cold wall surface (about 1215K-1530K) was carried out by the 'real time' laser light reflectivity method (LLRM) and the photographs of scanning electron microscope (SEM). The LLRM was used for measurement of deposition rates, due to thermophoresis (i.e. particle migration down a temperature gradient), of the small particles ($d_p<6㎛$), and the photographs of SEM were used for determining what factors control the collection of particles having diameters ranging from 0.2 to 30 microns. Two phenomena are primarily responsible for transport of the particles across the laminar boundary layer and deposition ; 1) particle thermophoresis; and 2) particle inertial impaction, the former effect being especially large factor of the particle deposition in its size over the range of 0.2 to 1 microns. And this study indicates that the thermophoresis can be important for the particles as large as 15 microns. Beyond $d_p= 16㎛$, this effect diminishes and the inertial impaction is taken into account as a dominant mechanism of the particle deposition. The results of the present experiments found to be in close agreement with several of the existing theories.
