Hydrodynamic experiments measuring longitudinal pressure-drop versus flow rate are conducted for turbulent flow of air (channel hydraulic diameter based Reynolds number range of 2300 to 6860) through near-compact heat exchanger models with rod bundles having aligned (inline) arrangement. Effects of the flow (Re), the geometry parameters, and number of rods of the test models on the nondimensional pressure-drop ξ are studied in detail. Treating the near compact heat exchanger model as a porous medium, a dimensional pressure-drop ΔP/L versus average velocity of flow (U) model similar in content to a non-Darcy porous medium model, is shown to fit the experimental data with fair accuracy. Variation in form drag related to, and induced by the flow and geometric parameters are shown to be the reason for the pressure-drop variations of different models. The relation between the porous medium type model (ΔP/L versus U) and the “ξ versus Re” model is discussed with careful attention to the differences in the two transitions viz. laminar to turbulent and viscous-drag to form-drag dominated flow inside the models. A proposed correlation for predicting ξ, ably capturing all of the form effects induced by the flow and geometric parameters, is found to give predictions with ±20% accuracy.

Keywords:
turbulence, hydrodynamics, heat exchangers, pipe flow, laminar to turbulent transitions, rods (structures), flow through porous media, drag, viscosity
Topics:
Drag (Fluid dynamics), Flow (Dynamics), Form drag, Fuel rods, Heat exchangers, Porous materials, Pressure drop, Rods, Turbulence
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