Turbulent swirling flows along the annulus formed between two concentric stationary cylinders have been studied. Hot-wire anemometry was used to detect radial variations of velocity components and the data presented in Part 1 of the investigation describes time mean measurements. Pressure measurements along the length of the outer, concave, cylindrical surface were obtained from wall tappings attached to a pressure transducer. Flow visualization using tufts indicated general swirl decay phenomena and these have been confirmed by the traverse data. The swirl flow rig was designed to incorporate suction systems to remove boundary layers from all walls preceding the test section. In this way the essentially free vortex generated by a circumferentially disposed set of guide vanes in the inlet bellmouth of the apparatus could be efficiently transferred to the test section entry region. This feature has not been incorporated by other workers and so their reported results depend on the upstream boundary layer flow, making correlation of data difficult. The data shown in this paper indicate the complex nature of swirling flow development in an annulus although it is not yet possible to be precise about the initial phases 相似文献
Direct contact heat transfer between water and a heat transfer oil was investigated under non-boiling conditions in co-current turbulent flow through a horizontal concentric annulus. The ratio of the inner pipe diameter to the outer pipe diameter (aspect ratio) κ = 0.730−0.816; total liquid velocity (mixture velocity) VT = 0.42−1.1 m/s; inlet oil temperature Toi = 38−94°C; oil volume fraction in the flowing mixture φo = 0.25−0.75 were varied and their effects on the overall volumetric heat transfer coefficient Uv were determined at constant interfacial tension of 48 dynes/cm.
It was found that, in each concentric pipe set, the overall volumetric heat transfer coefficient increased with increasing dispersed phase volume fraction at each constant mixture velocity and reached a maximum at around φo = φw ≈ 0.5. The maximum Uv values increased with increasing total liquid velocity and decreasing aspect ratio of the annulus. The volumetric heat transfer coefficient was also found to increase with increasing inlet oil temperature and increasing total liquid velocity but to decrease with length along the test section keeping all other parameters constant. Empirical expressions for the volumetric heat transfer coefficient were obtained within the ranges of the experimental parameters. 相似文献
The unsteady flow of non-Newtonian fluids through concentric and eccentric cylinders was investigated experimentally. Two experiments were carried out; one was pulsating flow and the other was flow under a constant pressure gradient with the inner cylinder oscillating longitudinally. The flow enhancement was examined and its dependence on the frequency of the oscillations and the eccentricity of the apparatus was determined. 相似文献
Spontaneous formation of concentric lamellae was observed in self‐assembling giant surfactants consisting of a fluorinated polyhedral oligomeric silsesquioxane (FPOSS) head and flexible polymer tail(s). Owing to the asymmetrical sizes of the head and tail blocks and the rectangular molecular interface, the giant surfactants assumed a truncated‐wedge‐like molecular shape, which induced morphological curvature during self‐assembly, thus resulting in the formation of curved and concentric lamellae. These curved/concentric lamellae were observed in FPOSS‐based giant surfactants with different architectures and compositions. The spontaneous curvature formation not only promotes our fundamental understanding of assembly principles, but also provides a promising and efficient approach to the fabrication of a wide range of high‐performance devices. 相似文献
The characteristics of the aerosols generated by pneumatic concentric nebulizers as well as sensitivities were studied in ICP-MS with a total of 26 nebulizers: 17 of the A-type, 6 of the C-type, and 3 of the K-type. Although of the same design, discrepancies in sensitivity were observed among the A1-30 type nebulizers. Free delivery rate, relation between the median of the volume drop size distribution, D50, and the capillary i.d., effect of the nebulizer gas exit cross sectional area on D50, energy transfer efficiency from the gas to the liquid stream and spatial homogeneity within the aerosol cones were studied. For a given nebulizer design, the gas exit cross-sectional area has shown to critically influence the aerosol characteristics. The aerosol generation mechanism has been explored and it has been concluded that, for A-type nebulizers the nebulization is more efficient than for C and K-type ones. The spray chamber design has also a marked effect on the results according to the particular nebulizer used. It has been observed that sample capillary was not perfectly centered with regard to the gas exit bore for several nebulizers. In order to minimize the problems associated with this bad alignment (i.e., different sensitivity depending on the nebulizer), spray chambers equipped with impact beads may be used, but to the detriment of the sensitivity. 相似文献
This paper describes a second-order method to calculate approximate solutions to flow of viscous incompressible fluid between rotating concentric spheres. The governing partial differential equations are presented in the stream–vorticity formulation and are written as a series of second-order equations. The technique employed makes use of second-order approximations for all terms in the governing equations and is dependent upon the direction of flow at a given point. This upwind technique has allowed us to generate approximate solutions with larger Reynolds numbers than has generally been possible for second and higher-order techniques. Solutions have been obtained with Reynolds numbers as large as 3000 and with grids as fine as a 40 × 40 mesh. Results are displayed in the form of level curves for both the stream and vorticity functions. A dimensionless quantity related to the torque acting on both spheres has been calculated from the approximate solution and compared with other results. Results with smaller Reynolds numbers such as 100 and 1000 are in excellent agreement with other published results. 相似文献