摘要:

A numerical study is performed on a three-dimensional model of heat transfer and fluid flow in the entrance region ( the flow is hydrodynamically and thermally developing) of radially rotating long channels with steady, laminar throughflow. The channel walls are isothermal. Consideration is given to channels of different geometries, including a square and both narrow and flat rectangles. Both the rotational speed and throughflow rates are varied. The velocity-vorticity method is employed in the formulation, and numerical results are obtained by means of a finite-difference technique. The Nusselt number, friction factor, and temperature and velocity distributions are determined, and the role of the Coriolis forte in the transport phenomena is investigated.

ISSN:1040-7782    

DOI:10.1080/10407789208944768

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A finite-volume approach is developed to numerically predict natural convection heat transfer in enclosures with isolated solid islands in the flow field. The computations were performed for the natural convection of air in a cylindrical envelope with an internal, concentric, slotted hollow cylinder for the range of Ra = - 103– 106and dimensionless slot width S = 0-0.5. The computed average equivalent thermal conductivities and the predicted flow patterns are compared with the experimental results available in the literature. It is found that for a fixed Rayleigh number there exists a critical slot width at which the total heat transfer rate reaches maximum.

ISSN:1040-7782    

DOI:10.1080/10407789208944769

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The interaction of natural convection with thermal radiation affects the transient response of a plate fin; this is studied analytically. The Rosseland approximation is applied to describe radiative heat transfer in the flow boundary layer. A cubic spline colocation method is used to perform the numerical computation. The important parameters of the problem are the aspect ratio, the convection-conduction parameter, and the radiation-conduction parameter. The results indicate that the time taken for the fin root to reach the specified temperature is almost independent of aspect ratio at large heat input. The surface heat flux is affected to a large extent by the convection-conduction parameter. The surface heat transfer rate increases with increasing radiative interaction. At large heat input, the temperature distribution at the base of the fin is nearly isothermal.

ISSN:1040-7782    

DOI:10.1080/10407789208944770

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The discrete-ordinate method was used to model the radiative heat transfer in an aluminum distributed combustion region resulting from the burning of aluminized solid propel-lant. The participating medium in the aluminum distributed combustion region, which consisted of gas and particle phases, had nonhomogeneous, emitting, absorbing, and anisotropic scattering radiative properties. In this study, the contribution from soot and gas radiation was neglected, and a one-dimensional gray analysis was used to study the radiant heat transfer from burning aluminum droplets and condensed aluminum oxide particles. The coupling effect of the energy and radiative transfer equations was studied by ( he iteration method through the divergence of the radiative heat flux vector term in the energy equation. Results showed that the coupling effect between the energy and radiative transfer equations was not significant. The decoupled equations predicted the radiative heat feedback about 5% higher than that predicted by the coupled equations. Several factors, such as aluminum loading of the propellant, pressure, agglomerate size of aluminum droplets, emissive properties of burning aluminum droplets, and albedo of aluminum oxide, which affected the magnitude of the radiative heat feedback, were also examined.

ISSN:1040-7782    

DOI:10.1080/10407789208944771

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Heated and unhealed jets discharging normally into a confined swirling crossflow are investigated numerically. Emphases are placed on the effects of temperature difference on the trajectory and mixing characteristics of the lateral jet in the swirling crossflow and the detailed impingement process of the opposed jets in the crossflow. Parameter variations studied include jet temperature, jet-to-crassflow velocity ratio, jet number, and swirl strength. Numerical errors are also discussed. The results show that the pressure force caused by the presence of the opposing jets will hinder the penetration and increase the velocity as the jets impinge. After impingement, the jet bifurcation phenomenon occurs, and the mixing path and the turbulence are greatly changed. Swirl prevents the jet from penetration due to the swirl-induced radial pressure gradient and the hydrodynamic instability. The spiraling jet flow in the swirling crossflow enhances turbulence near the tube center, and the swirl-generated turbulence can enhance the jet mixing. The jet-decaying process is almost independent of the temperature difference between the heated jet and the crossflow. The jet-spreading process is dependent on the inlet mass flux ratio and the mixing conditions.

ISSN:1040-7782    

DOI:10.1080/10407789208944772

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In this paper an expontial finite-difference scheme, first presented by Bhattacharya for one-dimensional, unsteady heat conduction problems in a plane wail, is used to solve various partial differential equations. Solutions of the unsteady diffusion equation in three dimensions and of the viscous form of Burgers’ equation ere used to illustrate the method. Predicted results are compared with exact solutions or with results obtained by other numerical methods.

ISSN:1040-7782    

DOI:10.1080/10407789208944773

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor