Performance of a Tube-bundle Heat Exchanger in a Rectangular-section Right-angle Bend Duct

Three-dimensional numerical simulations are conducted to elucidate the fundamental differences in hydrodynamics and heat transfer performance between heat exchangers arranged in confined rectangular-section right-angle bend ducts and those in straight ducts, with a specific focus on applications such as gas‑quenching furnaces. The effects of the tube-bundle arrangement and number of tube rows on the pressure drop (Δp) and heat‑transfer rate (Q) are examined under identical inlet conditions. Based on the performance differences, improved correlations are established for pressure drop and heat transfer performance applicable to rectangular bend ducts. The results demonstrate a definitive ordering of pressure drops: Δpss (staggered arrangement, straight duct) > Δpsi (in-line arrangement, straight duct) > Δpbi (in-line arrangement, bend duct) > Δpbs (staggered arrangement, bend duct), and a parallel hierarchy for heat‑transfer rates: Qₛₛ > Qₛᵢ > Qbᵢ > Qbₛ. Although staggered arrangements achieve only modest heat‑transfer gains over in-line arrangements, their marked reduction in pressure drop yields the optimal overall performance evaluation criterion. Both the friction factor fb and Nusselt number Nub of the bend duct increase with the number of tube rows, though their growth attenuates as the tube pitch decreases. These mechanistic insights lead to improved empirical correlations for predicting Δpb and Nub in bend ducts. Validations against simulation data show deviations within ±5%, effectively overcoming the limitations of straight-duct formulas in complex bend-duct geometries. These correlations provide a solid theoretical basis for optimizing the design and performance of bend-duct heat exchangers in confined spaces.