ENGINEERING METHODS OF CALCULATION OF DIFFERENT REGIMES OF HEATING OF THERMALLY MASSIVE OBJECTS IN METALLURGICAL HEAT TECHNOLOGIES UNDER COUNTERCURRENT CONDITIONS. 1. STATE OF THE PROBLEM. CONVECTIVE HEATING

摘要

Introduction. Heat exchange of parts of a solid body and a gas, moving in opposition, is widespread in industry and primarily in metallurgy. Cases of such heat exchange include heating of a charge in blast furnaces and of metal billets in continuous furnaces, cooling of pellets in stack-type coolers, dry quenching of coke, etc. Countercurrent processes of heat transfer are studied with different degrees of accuracy in [1-5]. Engineering computational procedures are most frequently based on the following simplifying assumptions [2]: (1) particles in the bed are considered as thermally thin insulated bodies; (2) heat exchange in the bed follows the Newton law (convection); (3) heat loss to the ambient medium is negligibly small; (4) there are no internal heat sources and sinks in the material heated; (5) heat transfer by conduction is disregarded. All five hypotheses are quite justified in countercurrent heat exchange in a dense bed of finely divided materials. In all other cases they can cause substantial errors, in particular, in thermal calculations of heating of a metal in continuous furnaces.