The development of rationalized correlations for f and j for forced air-flow convection in rectangular offset-strip-fin cores is presented in this study with 100 ≤ Re ≤ 8000. New experimental data and three-dimensional conjugate heat transfer computational simulations were acquired to understand the flow physics and heat transfer phenomena. The offset arrangement of the fins disrupts the fully-developed condition prevalent in plain fins to promote secondary flow and enhanced heat transfer, and this effect is found to be fundamentally scaled by offset length ratio λ (=l/dh. Furthermore, because of the blunt surface edge or finite thickness of the offset fin, the flow stagnation and wake effects are integral parts to the secondary flow. The influence is found to be characterized by the thickness ratio ζ (=tRe/dh) as well as the rectangular flow cross-section aspect ratio α (=s/hf. New models are proposed for f and j in both laminar and turbulent regimes based on the enhanced convection effects, which are represented by these scaling parameters, and are superimposed on the fully-developed condition in a rectangular channel. The correlations are thereby devised from the new sets of experimental data as well as that given in the open literature, and thus cover a wide range of λ, ζ, and α. Because the transition from laminar to turbulent regimes is smooth and continuous, the general correlations of f and j are developed by asymptotic matching as single expressions and are shown to predict the extended dataset to within ±20%.

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