SOME ASPECTS OF THE STABILITY OF VERTICAL PNEUMOTRANSPORT OF SOLID PARTICLES Yu. S. Teplitskii and V. I. Kovenskii UDC 533.6 The upper boundary of the critical transition region separating stable (normal) pneumotransport from a through two-phase flow with internal circulation of the particles is determined on the basis of an analysis of pressure losses in a two-phase flow in a vertical channel. Simple dimensionless relations for calculation of the velocities Ucl and Uopt determining the lower and upper boundaries of the transition region are obtained. JEPTER74920199912 JEPTER7492012