摘要:

Heat transfer to constant-property, fully developed, laminar flows in circular-segment ducts with uniform wall temperature (T) has been analyzed. Besides representing a compact surface, the segment duct geometry models the flow cross section of a circular tube with a straight-tape insert. Two variations in the T thermal boundary condition are considered: constant axial and circumferential wall temperature, and constant temperature on the curved surface but an adiabatic flat wall. These two conditions model the extremes of the fin effects of a straight-tape insert, i.e., 100% and zero fin efficiencies, respectively. Numerical solutions, obtained by using finite difference techniques, are presented for both the velocity and temperature fields. The isothermal friction factors are in excellent agreement with analytical solutions reported in the literature. The Nusselt number results for the two thermal boundary conditions are presented for different segment shapes, 0° ≤, 6 ≤, 90°, and they represent the lower limits of the heat transfer enhancement due to twisted-tape inserts.

ISSN:1040-7782    

DOI:10.1080/10407789408956006

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A top pee liquid layer is heated from the bottom in a two-dimensional rectangular container with insulated side walls. The resulting thermacapiUary motion is predicted by the projection method involving a Godunov-type discretization for convective terms. The velocity and temperature fields beyond those predictable via infinitesimal theories are discussed in terms of the Marangoni number, Prandtl number, Biot number, and aspect ratio.

ISSN:1040-7782    

DOI:10.1080/10407789408956007

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A thermal analysis of floor healing panels is presented, based on well-known theoretical results concerning shape resistance factors. Finite element calculations are utilized to modify the standard expression of shape resistances, in order to take into account the distribution of heat flow lines in floor panels and the influence of nonuniform surface temperatures. The results obtained by the proposed method compare favorably with the calculations based on a recent code of practice and are in good agreement with those of finite element simulations and experimental measurements.

ISSN:1040-7782    

DOI:10.1080/10407789408956008

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The effect of vertical eccentricity on natural convection in a rhombic annulus is studied numerically for enclosure gap values (ER) of 0.5 and 0.75, eccentricity (ϵ) values from -0.25 lo 0.25, and Rayteigh numbers (Ra) from I04to 108Negative values of t (inner rhombus displaced downward) lead to an increase in heat transfer. At low Ra there is a critical positive e for which the flow strength is a maximum. At high Ra, increasing positive e results in a decrease in the flow strength and heat transfer. For any ϵ > 0 there is a critical Ra, beyond which there is a decrease in the total heat transfer. This critical Ra increases with decreasing ERvalues.

ISSN:1040-7782    

DOI:10.1080/10407789408956009

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

This paper presents a numerical scheme for the solution of unsteady velocity and temperature fields in an enclosed compressible fluid that is subjected to thermally induced mechanical motion. The numerical scheme includes revisions of earlier models as well as a scheme applied to the simplified form of the governing equations. The results are compared with previous numerical results and available analytical solutions. The fluid unsteady temperature profile is also compared with recent experimental results. The suggested numerical revisions are shown to improve the results significantly, as verified by experimental data.

ISSN:1040-7782    

DOI:10.1080/10407789408956010

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The peculiarities of pulsed laser melting and evaporation of the superconducting ceramics are analyzed by means of numerical simulation. The appearance of the overheated metastable states in solid and liquid phases is shown as a result of the phase front dynamics and volume nature of laser energy release. A method of dynamic adaptation for the multifront Stefan problem is proposed.

ISSN:1040-7782    

DOI:10.1080/10407789408956011

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The surface-tension-driven convection in laser melting has been simulated by the Galerkin finite element method. The governing laminar, axisymmelric convection equations are solved in a sequential manner by an explicit projection method. The numerical results show a strong dependence of the flow pattern on the value of the temperature coefficient of surface tension (σT). Results are presented for a range of σTvalues typical in steel, -l0−4≤σT+ l0−4N/mK. As the melt depth is more affected than the width, the melt aspect ratio changes due to convection. The melt pool is broad and shallow when σT< 0, and deep and narrow when σT> 0.

ISSN:1040-7782    

DOI:10.1080/10407789408956012

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor