OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 7 No. 3 2025 These results demonstrate that pulsation, particularly when applied downstream, significantly enhances HT through increased turbulence, vorticity, and velocity variations. The primary mechanisms contributing to improved heat transport in pulsating flows are enhanced eddy formation and the generation of shear layers. Conclusion The enhancement of heat transfer (HT) in a circular pipe with surface roughness under turbulent flow conditions was investigated using a combined experimental and computational approach. The study focused on the effects of surface roughness, pulsation frequency (f), Reynolds number (Re), heat input (Q), and amplitude (A) on HT characteristics. Key parameters evaluated included velocity, pressure, and temperature distributions, turbulent kinetic energy (TKE), vorticity, eddy viscosity, the surface HT coefficient (h), and the Nusselt number (Nu). The following key conclusions can be drawn from the results: 1. TKE as a driver of HT enhancement: a) TKE is critical for the production and sustenance of turbulence, which dominates the pulsating heat transfer mechanism. b) Increased TKE strengthens fluid-wall interactions, enhancing convective HT, particularly with downstream pulsation as observed in this study. c) These results align with those of previous studies [2, 3, 4], even those that did not consider roughness effects [60]. Fig. 12. Turbulent kinetic energy (TKE) contour plots in the mid y-plane for Re = 6,753, heat input Q = 954 W/m², pulsation amplitude A = 0.1, pulsation frequency f = 1 Hz at upstream pulsation
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