摘要:

Flow and temperature fields were numerically analyzed in a bench-scale gas-injected molten steel bath. A cylindrical vessel containing molten steel was considered. A stream of argon was injected vertically upward through a nozzle located at the bottom center of the vessel. The problem was formulated on the basis of a two-fluid model using the Eulerian approach for both gas and liquid phase transports. Effects of gas flow rate on flow field and on intensity of mixing in the bath were investigated in isothermal systems. To study heat transfer mechanisms between the gas and melt, temperature field equations were solved for both phases in a nonisothermal system.

ISSN:1040-7782    

DOI:10.1080/10407789208944883

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A numerical investigation is conducted of turbulent convection in a longitudinally conducting, externally finned pipe. Results reveal significant enhancement in heat transfer due to finning. The heat transfer rate to the fluid increases with increasing thermal conductivity of the pipe wall, with increasing values of the external heat transfer coefficient, and with decreasing interfin spacing. Heat transfer is underestimated by as much as 30 times in the developed region when the thermal conductivity of the pipe wall is not accounted for. The magnitude of this underestimation decreases with decreasing wall conductivity. Finning is found to be most effective at low values of wall conductivity, where a nearly 10-fold increase in heat transfer is noted. At high thermal conductivities in the wall, the Nusselt number and the pipe wall temperature vary monotonically in the axial direction, and this variation becomes increasingly nonmonotonic at lower thermal conductivities. A constant, spatially averaged, Biot number solution is found to give satisfactory results only for cases of high conductivity in the wall. The asymptotically developed Nusselt numbers compare well (within 7%) with the axiatty averaged values for the cases of conducting pipe wall.

ISSN:1040-7782    

DOI:10.1080/10407789208944884

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Conjugate mixed convection-conduction heat transfer from a vertical, cylindrical fin embedded in a saturated, high-porosity, porous medium is analyzed. The effects of both boundary and inertia forces were taken into account. The numerical solutions of the problem are obtained by a local nonsimilarity method. Results were obtained for the surface curvature parameter 𝛌 = 1, 2, and 4 and other parameters in the range of 0 ≤ Ncc≤ 2.0 and 0 ≤ Ω ≤ 2.0. The heat transfer coefficients are found to follow trends similar to those of the classical fluids. Both boundary and inertia effects decrease the heat transfer rate and become more significant for mixed convection flow, especially downstream and at large values of N NccThe total heat transfer rates are higher for lower values of 𝛌, that is, for larger fin radius r No

ISSN:1040-7782    

DOI:10.1080/10407789208944885

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The time-averaged Navier-Stokes equations are solved numerically by a finite-volume method and applied to study flow around two-dimensional bluff bodies. The finite-volume equations are formulated in strong conservative form on a general, nonorthogonal grid system. The resulting equations are then solved by an implicit, time marching, pressure-correction based algorithm. If the flow problem has a steady state solution, then it is obtained by taking sufficient time steps until Ike flow field remains unchanged with time. As test cases for the developed methodology, two problems are selected; one has a steady state solution and the other has only a transient solution. Numerical predictions are obtained with the standard k-ε turbulence model for the steady state, turbulent flow problem. The k-ε model was able to predict the major, experimentally observed flow characteristics including the small separation bubble near the rear end of the body selected for the steady state test case. For the transient test case, the algorithm correctly captured the transient nature of the problem. However, agreement with the experimental results was only moderate because of the lower order differencing scheme employed in the method.

ISSN:1040-7782    

DOI:10.1080/10407789208944886

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Fluid flow and temperature fields in the two-dimensional vertical plane of a reservoir are numerically modeled for inflow Reynolds number R0in the range 100-1000 and inflow densimetric Froude number F0in the range 0.5-50,0. Both surface inflow and submerged inflow were studied for reservoir slopes of 45° and 90°. Numerical experiments show that the flow fields and temperature distributions in the reservoir are primarily a function of F0, while the dependence on R0is implicitly coupled to F0. The strengths and extent of recirculation of the flow fields in the reservoirs were observed to be characterized by functions that are directly proportional to l/F20and R0.

ISSN:1040-7782    

DOI:10.1080/10407789208944887

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Forced convective heat transfer in the entrance region of a confined turbulent jet is studied numerically. The solution of the transport equations is based on a combination of an iterative, finite-volume computational procedure using primitive dependent variables and a two-equation turbulence closure model. The separated flow zone, which extends as far as three pipe diameters, is observed to be a site of high turbulence. The heat transfer results show little sensitivity to the total number of grid points. The variation of the Nusselt number is influenced by the growth of the thermal boundary layer and the presence of the separated zone. Locations of the minimum and maximum Nusselt numbers are found to be functions of the Craya-Curtet number. Finally, the heat transfer predictions are clearly shown to be sensitive to the location of the grid point next to the wall.

ISSN:1040-7782    

DOI:10.1080/10407789208944888

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Heat transfer in the thermal entrance region of pipes is analyzed by the finite-difference method including the effect of axial fluid conduction. A hydrodynamically developed flow through a two-region pipe is investigated for constant surface temperatures by a step change and for insulated upstream and uniform wall heat flux in the downstream region. The rate of convergence is enhanced by discretizing the governing differential equation by an exact profile obtained from the analytical solution of the one-dimensional conduction-convection problem.

ISSN:1040-7782    

DOI:10.1080/10407789208944889

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor