Numerical simulation of heat transfer and hydraulic losses of air-cooled exhaust-shaft apparatuses

Abstract

The article presents the numerical simulation results on heat transfer and hydraulic losses of air-cooled exhaust-shaft apparatuses. Studies were made on air-cooled apparatuses in which four-row bundles of staggered finned tubes were placed. Numerical simulation used a gas dynamic solver Ansys Fluent. Menter’s shear stress transport κ-ω model was invited to close the Reynolds equations. The obtained numerical results allowed us to visualize air flow in the bundle and the exhaust shaft, as well as to establish an inhomogeneous distribution of velocities and temperatures. We found that the temperature distribution in the flow passing through the exhaust shaft depends on the height of the exhaust shaft. We also established that at small shaft heights in the wake behind a bundle because of the wake oscillatory motion, the dynamic and temperature inhomogeneous distributions take place, resulting in the cold air suction through the shaft from the environment. With an increase in the shaft height, the inhomogeneous temperature distribution moves upstream the air flow in the shaft and the inhomogeneous temperature distribution attenuates. We can say that maximum heat transfer at the same hydraulic losses is achieved when mounting a shaft with a height of H > 1.16 m. The results obtained can be used for the modernization of existing air-cooled apparatus, as well as for the design of new devices with an exhaust shaft.