OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 7 5 Ta b l e 6 Experimental HT Coefficient and Nu for Different Res and Frequencies for Q = 25 W. DS= downstream; US=upstream Reynolds number hexpt. Nuexpt. f = 1.0 Hz f = 3.33 Hz f = 1.0 Hz f = 3.33 Hz Re DS US DS US DS US DS US 6753 32.91 28.21 47.15 39.99 30.96 26.54 44.36 37.62 9504 35.9 30.97 51.79 43.88 33.77 29.13 48.72 41.28 11618 38.53 31.59 58.5 47.15 36.25 29.72 55.03 44.36 13414 45.13 36.31 60.75 56.41 42.46 34.16 57.15 53.07 a b c d Fig. 8. Changes in Nu and h values as a function of Re for various pulsation frequencies at heat inputs of Q = 25 W and Q = 100 W Numerical Results Although the heat transfer (HT) coefficients and Nusselt number (Nu) values are derived from experiments, simulations provide a better understanding of the influencing flow mechanics. Fig. 9 displays vorticity contours under upstream pulsation for Re = 6753, Q = 954 W/m², A = 0.1, and f = 1 Hz. Shear-
RkJQdWJsaXNoZXIy MTk0ODM1