Hydrodynamics and Heat Transfer to Vertically Flowing Gas-Solids Suspensions

Abstract

Vertically flowing gas-solids suspensions have been investigated both theoretically and experimentally. The theoretical approach suggested the possibility of self-similar flow patterns for the particles at low solids concentration. The experiments carried out on two different installations with four different solids confirmed the existence of a so-called similar profiles regime bounded at dilute-phase flow conditions. At a constant gas velocity, a sudden transition occurs for a critical solids concentration. Beyond this limit particle concentration increases faster with increasing solids rate. These similarity properties have been eventually extended to the temperature profiles, which allowed the derivation of a general wall-to-suspension heat transfer equation containing two shape factors summarizing the flow hydrodynamics. This equation proved to be in excellent agreement with experimental results. Moreover, beyond the flow regime transition, i.e. in dense-phase flow, the same equation applies with modified shape factors.