© Fluid Flow And Heat Transfer Characteristics In Axisymmetric Annular Diffusers Shuja, SZ; Habib, MA PERGAMON-ELSEVIER SCIENCE LTD, COMPUTERS FLUIDS; pp: ; Vol: 25 King Fahd University of Petroleum & Minerals Summary The present paper provides and validates a numerical procedure for the calculation of turbulent separated Bow and heat transfer characteristics in axisymmetric expanding ducts, with emphasis on the annular diffuser geometry. The method is based on the fully-conserved control-volume representation of fully elliptic Navier-Stokes and energy equations in body-fitted orthogonal curvilinear coordinate systems. Turbulence is simulated via the two-equation (k-epsilon) model. The presented results consist of computed velocity and streamline distributions, the kinetic energy of turbulence and local and average Nusselt number distributions. Systematic variations are made in the Reynolds number (6 x 10(3)-6 x 10(5)) and the outer wall half angles (7 degrees-20 degrees, 90 degrees). The study was further extended to flows with a range ( ) of inlet swirl number. Comparison with available experimental data shows that the method with the utilized turbulence closure model and the discretization scheme reproduces the essential features of various diffuser heat transfer and fluid flow effects observed in the experiments. The degree of heat transfer coefficient enhancement, both maximum and average, increases strongly as the wall cant angle increases. The peak, average and exit Nusselt numbers exhibit clear dependence on the Reynolds number and were well correlated with similar to Re-2/3, as was previously encountered in the literature for other types of separated regions. Although there is some indication that the exponent increases to similar to 0.8 for Re > 50,000. Local heat transfer rates have been shown to increase with the increase of swirl number and to peak near the reattachment point. Copyright: King Fahd University of Petroleum & Minerals;

© References: ADENUBI SO, 1976, ASME, V98, P236 AGRAWAL AK, 1991, 91GT62 ASME BAUGHN JW, 1984, J HEAT TRANS-T ASME, V106, P789 BAUGHN JW, 1987, J HEAT TRANS-T ASME, V109, P37 BERNER C, 1984, ASME, V106, P743 BRADSHAW P, 1973, EFFECT STREAMLINE CU CHANG PK, 1970, SEPARATION FLOW, P158 ELGAMMAL AH, 1981, J MECH ENG SCI, V23, P107 ELKERSH AM, 1985, P I MECH ENG C-MECH, V199, P293 FISHENDEN CR, 1977, J AIRCRAFT, V14, P60 GARCIA A, 1987, J HEAT TRANS-T ASME, V109, P621 GOSMAN AD, 1979, TURBULENT SHEAR FLOW, V1, P237 GUPTA AK, 1984, SWIRL FLOWS HABIB MA, 1979, J FLUIDS ENG, V101, P521 HABIB MA, 1982, NUMER HEAT TRANSFER, V5, P145 HABIB MA, 1988, ASME J TURBOMACHINER, V110, P405 INCROPERA FP, 1985, INTRO HEAT TRANSFER KRALL KM, 1966, J HEAT TRANSFER, V88, P131 LANYUK AN, 1988, POWER ENG, V26, P121 LAUNDER BE, 1972, MATH MODELS TURBULEN LAUNDER BE, 1976, TURBULENCE, P279 LILLEY DG, 1973, AIAA J, V11, P955 LILLEY DG, 1976, AIAA J, V14, P749 LOHMANN RP, 1979, ASME, V101, P224 PATANKAR SV, 1972, INT J HEAT MASS TRAN, V15, P1787 SHYY W, 1985, COMPUT METHOD APPL M, V53, P47 SOVRAN G, 1965, FLUID MECH INTERNAL, P270 SREENIVASAN KR, 1983, PHYS FLUIDS, V26, P2766 STEVENS SJ, 1973, J AIRCRAFT, V10, P73 STEVENS SJ, 1980, ASME, V102, P357 ZEMANICK PP, 1970, ASME J HEAT TRANSFER, V92, P53 For pre-prints please write to: Copyright: King Fahd University of Petroleum & Minerals;