http://yetl.yabesh.ir/yetl1/handle/yetl/19034 Mon, 20 Apr 2026 22:11:36 GMT 2026-04-20T22:11:36Z http://localhost:80/yetl1/bitstream/id/184275/ http://yetl.yabesh.ir/yetl1/handle/yetl/19034 http://yetl.yabesh.ir/yetl1/handle/yetl/4295326 Exact Insulated-Tip Fin Length Correction for Tip Convection Compensation Capobianchi, Massimo; Cangelosi, Richard This study details the derivation of a length correction term for computing the heat transfer performance of one-dimensional, straight, convecting-tip fins using the insulated-tip fin solution. Use of this corrected length in the insulated-tip fin solution produces the identical heat transfer rate and temperature profile as those computed using the more complex convecting-tip fin equations. The analysis derives the length correction equation from fundamental principles and produces a simple, closed-form expression valid for all fin cross-sectional shapes. Furthermore, the valid parameter range where this length correction is applicable, and outside of which no exact length correction is possible, is quantified. Mon, 01 Jan 2024 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4295326 2024-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4295325 Non-Isothermal Plane Couette Flow and Its Stability in an Anisotropic and Inhomogeneous Porous Layer Underlying a Fluid Layer Saturated by Water Barman, N.; Aleria, A.; Bera, P. In this article, the linear stability of nonisothermal plane Couette flow (NPCF) in an anisotropic and inhomogeneous porous layer underlying a fluid layer is investigated. The Darcy model is utilized to describe the flow in the porous layer. The stability analysis indicates that the introduction of media-anisotropy (K*) and media-inhomogeneity (in terms of inhomogeneity parameter A) still renders the isothermal plane Couette flow (IPCF) in such superposed fluid-porous systems unconditionally stable. For NPCF, three different modes, unimodal (porous or fluid mode), bimodal (porous and fluid mode) and trimodal (porous, fluid and porous mode), are observed along the neutral stability curves and characterized by the secondary flow patterns. It has been found that the instability of the fluid-porous system increases on increasing the media permeability and inhomogeneity along the vertical direction. Contrary to natural convection, at d̂=0.2 (d̂=depth of fluid layer/depth of porous layer) and K*=1, in which the critical wavelength shows both increasing and decreasing characteristics with increasing values of A (0≤A≤5), here in the present study, the same continuously decreases with increasing values of A. Finally, scale analysis indicates that the onset of natural convection requires a relatively higher temperature difference (ΔT) between lower and upper plates in the presence of Couette flow. However, by including media anisotropy and inhomogeneity in the porous media, the system becomes unstable even for a small critical temperature difference of about 2 °C. Mon, 01 Jan 2024 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4295325 2024-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4295324 Buoyancy and Velocity Field Synergy Principle in Convective Heat Transfer and Its Role in Thermo-Hydraulic Performance Improvement Yang, Dong; Hu, Xinyue; Chen, Feilong; Liu, Yingli This study proposes the buoyancy and velocity field synergy principle and aims to enhance thermo-hydraulic performance in convective heat transfer. A mechanical energy conservation equation concerning synergy between buoyancy and velocity was derived, which describes the mechanical energy transport and dissipation in convective heat transfer. Two new field synergy numbers, FsU,g and FsU,∇p, were proposed to characterize the degree of synergy between velocity and buoyancy, and the degree of synergy between velocity and pressure gradient over the fluid domain, respectively. The pressure drop of a channel subjected to convective heat transfer is related to not only Gr/Re2 but also FsU,g. Under a same Gr/Re2, a larger |FsU,g| leads to a smaller |FsU,∇p|, and thus the pressure drop is decreased. Furthermore, the multifield synergetic relationships among buoyancy, velocity, temperature gradient and pressure gradient were analyzed for convective heat transfer in channels. The correlation between FsU,∇p and (Gr/Re2)FsU,g, and the correlation between FsU,g and a traditional field synergy number characterizing convective heat transfer capability, Fc, were derived, which reveals the coupled mechanisms of mechanical energy dissipation and thermal energy transport in convective heat transfer. The proposed principle was applied in typical channel flows subjected to convective heat transfer, and its benefits were demonstrated. It is noted that both pressure drop reduction and convective heat transfer enhancement can be achieved in convective heat transfer using the proposed principle. This paper provides a new insight for improving thermo-hydraulic performance of heat exchangers. Mon, 01 Jan 2024 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4295324 2024-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4295323 Turbulent Pulsating Convective Flow in the Quasi-Steady and Low-Frequency Regimes Banerjee, Ayan Kumar The instantaneous and time-averaged dynamics of turbulent pulsating convective pipe flow is investigated experimentally over Strouhal number, St=3.3×10−4−0.12 that falls in the quasi-steady and low-frequency regimes, pulsation amplitude, βb=0.05−0.2, and bulk Reynolds numbers, Reb=7528−10,920. The analytical expressions for pulsation amplitudes of centerline velocity, bulk velocity, and Nusselt number are derived. The time series of oscillating components of centerline velocity (Uc˜), cross-sectionally averaged bulk velocity (Ub˜), and Nusselt number (Nu˜) depicts that the phase differences between Uc˜, and Ub˜, and between Ub˜, and Nu˜ increase with St nonmonotonically with near zero phase difference at St→0. The time-averaged pulsating Nusselt number Nu¯ is invariant of St for St > 0.01. Nu¯ depends marginally on βb. The relative mean Nusselt number, Nur=Nu¯/Nus<1 for Reb≥8885 and Nur>1 for Reb = 7528. The general observations from this study is that, in the quasi-steady and low-frequency regimes, turbulent pulsating flows leads to marginal changes in the time-averaged Nusselt number Nu¯ compared to the time-averaged Nusselt number Nus in steady flow condition at any Reb. Mon, 01 Jan 2024 00:00:00 GMT http://yetl.yabesh.ir/yetl1/handle/yetl/4295323 2024-01-01T00:00:00Z