Features of Gravitational Flow of Heated Air in an Exhaust Shaft Above a Multirow Finned Bank

Abstract

The authors have carried out investigations into the introduction of hot-air heating systems in buildings and structures, and also the applicability of mixed convection in calorifers of recirculating air heaters. The heat transfer of two- and four-row staggered air-heater banks consisting of bimetallic finned tubes in mixed convection has been studied. Experimental investigations into the characteristics of a gravitational flow of heated air in an exhaust shaft above a heat-exchange bank in a mixed-convection regime have been presented. An increase of 1.5–3 times in the heat transfer in the mixed-convection regime compared to the heat transfer under conditions of free convection of the air has been established. The dynamics of motion of a geyser flow of heated air in the exhaust shaft above the heatexchange bank under gravity has been described. A decline of 20–50% in the heat transfer of staggered two- and four-row banks because of the presence of geyser air flows has been established. A method to diminish the adverse impact of geyser air flows on the heat transfer of the bank has been proposed.