摘要:

Numerical simulations, based on a control-volume-based finite difference method with central differencing and semi-implicit time marching, are performed for natural convection of liquid metals within a square cavity. All calculations are made with the Prandtl number held constant at 0.005, while Grashof numbers of 3 × 106and 107are considered with both steady and time varying sidewall temperatures. With steady boundary conditions and the assumption of two-dimensional convection, periodic and quasi-periodic conditions, respectively, are predicted for Gr equals 3 × 106and 107, and the oscillatory states are related to the transport of thermal energy and vorticity. The effects of small and large cooling rates on predicted convection are considered. It is found that the small cooling rates have a negligible effect on the dynamic behavior of the system, while large cooling rates cause transitions to more complex flow structures and enhance mixing.

ISSN:1040-7782    

DOI:10.1080/10407789608913812

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A numerical study of the turbulent natural convection-radiation interaction and the associated heat transfer in a square enclosure with differentially heated vertical walls and insulated horizontal walls is reported. The enclosure is either filled with a single participating gas (H2O or C02) or a homogeneous mixture of two participating gases along with a diluent (N2). A two-dimensional computational domain was used to simulate the steady state turbulent flow within the enclosure. The surface and gas radiation were treated by the discrete ordinates method. The wavelength dependent radiative properties of the gases were considered by the ‘weighted sum of gray gases’ model. A new correlation relating Nusseli number at the isothermal vertical walls as a function of the Rayleigh number and optical thickness of the medium is proposed. Detailed information about heat transfer variations along the length of the vertical walls is also given. The results are compared with previous numerical data obtained by other radiation models for similar problems.

ISSN:1040-7782    

DOI:10.1080/10407789608913813

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

An effective numerical method was developed for analyzing, as a conjugate problem, transient two-dimensional heat and mass transfer between a solid desiccant and a humid laminar airstream. The method is also more generally applicable to conjugate problems of heat and mass transfer between solids and flowing fluids. The alternating direction implicit (ADI) procedure with an upwind scheme is used for solving both the energy and mass transfer equations. The secant method is applied to solve the local equilibrium relationship between the water content and the water vapor concentration in the silica gel bed. Comparison with conventional, nonconjugate problem solutions has shown that such solutions produce unacceptably large errors in thick-bed (of the order of 2 cm) desiccant systems; for example, they overpredict the water absorption rates by 53%.

ISSN:1040-7782    

DOI:10.1080/10407789608913814

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A numerical method has been used to predict the combined convection flow of Newtonian fluids in vertical eccentric annuli, in which the inner and outer walls are held at different temperatures. Assuming that the ratio of the radial to the vertical length scale, e, is small, as found in many industrial applications, then the full steady, momentum, energy, and continuity equations are simplified by expanding the variables in the governing equations in terms of e. The parabolic nature of the simplified equations allows a marching procedure in the vertical direction using a finite difference scheme, and the resulting equations can be solved at each vertical step using the finite element method. Results have been obtained for a range of the governing parameters, namely, the Grashof, Prandtl, and Reynolds numbers.

ISSN:1040-7782    

DOI:10.1080/10407789608913815

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The problem with simultaneous conductive, connective, and radiative heat transfer is analyzed in a two-dimensional gradual expansion channel flow. The main objective is to generate a program to attack the radiation in a curvilinear coordinate system with momentum and energy equations involved. The governing equations are transformed into generalized coordinates. Whereas the SIMPLE algorithm developed in a body-fitted coordinate system is used to obtain the flow field solution, the finite volume method is applied to solve the radiative transfer equation. The accuracy and performance of the finite volume method for the radiation are validated in a well-known combined heat transfer problem by using a curvilinear grid system. Then detailed thermal characteristics are investigated in a gradually expanding channel through various parameters such as Prandtl number, conduction to radiation parameter, wall emissivity, and scattering albedo. Results show that radiation plays a significant role in the gradually expanding channel flow.

ISSN:1040-7782    

DOI:10.1080/10407789608913816

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The complicated flow fields in miniature annular combustors are investigated numerically. The flow parameters studied include the jet tube length and momentum ratio of the primary jet. From the numerical results it is found that four different recirculations, namely, the primary, second, third, and dilution recirculations, might be generated in the combustor owing to the interaction between the mainstream and the lateral jets. In all cases studied, the primary recirculation can be observed, although its strength, size, and location are changed with the flow parameters. The jet tube length produces a significant effect on the recirculation flow structure in the primary zone. The increase of the momentum ratio of the primary jet results in the suppression and enhancement of the primary and second recirculations, respectively.

ISSN:1040-7782    

DOI:10.1080/10407789608913817

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor