摘要:

A numerical study of a turbulent gas-liquid droplet flow is presented using the Lagrangian approach for the discrete phase and the Eulerian approach for the continuous phase. The spray nozzle is mounted on the wall of a two-dimensional plane channel, The influence of different directional angles as well as the angle of spray on the velocity and temperature field of the main phase are studied. Three sine categories are used to model the spray with the mean mass diameter of I mm, Two different spray angles are defined, namely 10° and 60°, The average directional angle varies (measured from the wall) from 60° to 120°.

ISSN:1040-7782    

DOI:10.1080/10407789408955977

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Flow and heat transfer are studied numerically in a duct of rectangular cross section with a moving wall. The temperature of the moving wall is assumed to be constant while the other three walls are insulated. This boundary condition has important applications in the design of oil-cooled friction pairs. Results are presented for wall Reynolds numbers of 0, 100, 500, and 2500; Prandtl numbers of 0.7, 10, 50, and 100; and cross-sectional aspect ratios of 0.5 and 1. It is found that flow and heat transfer are strongly affected by an interaction between the boundary layer on the moving wall and a recirculation zone set up by that wall. In particular, the Nusselt number shows an interesting maximum before fully developed conditions are established. This maximum is believed to result from the enhancing effect of the widening recirculation zone as fully developed conditions are approached. Hydrody-namic and thermal entrance lengths are drastically reduced with increasing wall Reynolds number. This behavior can be used to advantage in the optimal design of grooved, oil-cooled friction pairs such as wet clutches.

ISSN:1040-7782    

DOI:10.1080/10407789408955978

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A numerical investigation of five surface transport within a hollow glass ampule with feed-in boundary conditions is presented. The glass ampule is treated as a vertical film with a finite pressure difference across the film, with applied influx on the upper boundary, and with applied heat flux at the outer free surface. Two different sizes of glass ampules, along with different influx values art investigated. A finite element method with full consideration of surface tension and viscosity effects is used to solve the transient Navier-Stokes equations in cyclindrical coordinates. Radiative and connective boundary conditions are incorporated when solving the energy equation. The movement of the inner and outer free surfaces with the specified feed-in velocity for different dimensions and temporal temperature distribution are analyzed. It is found that the feed-in mechanism rather than the pressure difference provides the more dominant driving forces. Also studied is the effect of using different feed-in velocities on the flow and temperature fields. The results presented in this work illustrate the basic effects of the feed-in mechanism of the free surface transport phenomenon.

ISSN:1040-7782    

DOI:10.1080/10407789408955979

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Combined convection and radiation in simultaneously developing laminar flow and heat transfer in a smooth tube is numerically considered with the P-I approximation and the exponential wideband model. The fluid is a mixture of carbon dioxide, water vapor, and nitrogen, The bulk mean temperature variation, temperature profiles, and Nusselt numbers are shown for a uniform inlet temperature and several constant wall temperatures. Nusselt numbers for simultaneously developing flow are compared with those for thermally developing flow. The effects of the mole fraction of the nongray gases and the wall emissivity on convective and radiative Nusselt numbers are explored.

ISSN:1040-7782    

DOI:10.1080/10407789408955980

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A source-and-sink method has been developed for the solution of both ablation and combination of ablation and Stefan problems for a one-dimensional, subcooled medium imposed with both constant and time variant heat flux conditions. In this method the problem is solved in a fixed domain, so that the original heat flux condition imposed on the moving boundary is taken to be the condition imposed on the solid-vapor or liquid-vapor interface. This flux condition can then be used together with the temperature at the interface to solve for the interface position as well as the condition imposed on the fixed boundary. Finally, these interface position and boundary conditions are used in the temperature equation to complete the solution. The method has been used successfully in solving seven examples encompassing one-, two-, and three-phase ablation with the boundary of the medium imposed with constant, linear, and quadratic flux conditions. Numerical solutions for these examples as well as the trends of the moving boundary positions are discussed in detail.

ISSN:1040-7782    

DOI:10.1080/10407789408955981

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Periodic fully developed fluid flow and heat transfer characteristics are obtained numerically for turbulent flow over a three-dimensional array of heated square blocks deployed along one wall of a parallel-plate duct. This configuration simulates forced convection cooling of electronic equipment. The Lam-Bremhorst low-Reynolds-number form of the k - ε model is used for the computations. The computations are performed for a set of geometric parameters characterizing the array, for a range of Reynolds numbers from 103to 104, for a Prandtl number of 0.7, and for a condition of uniform wall temperature. The results are compared with relevant experimental data from the literature and also with the numerical values obtained by using the high-Reynolds-number form of the k - ε turbulence model.

ISSN:1040-7782    

DOI:10.1080/10407789408955982

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A nonisothermal model of Ike single screw extrusion processing of generalized Newtonian fluids is presented. Various temperature dependent forms of a generalized Newtonian fluid constitutive equation representing the Herschel-Bulkley fluid and its simplifications, including Bingham plastic, power law of Ostwald-de Waele, and Newtonian fluids, are applicable. The model includes the generally ignored transverse convection terms of the equation of energy. The importance of keeping the transverse convection terms in the analysis is demonstrated by applying the model and comparing findings to experimental results involving the transverse flow temperature distributions in single screw extruders, available in the literature. The numerical instabilities, arising principally from the convection terms, generally encountered in high-Péclet-number extrusion flows, could be eliminated by the use of the streamline upwind / Petrov-Galerkin formulation. The model is sufficiently general to accommodate Navier's wall slip at the wall boundary condition commonly encountered during the processing of gels and concentrated suspensions.

ISSN:1040-7782    

DOI:10.1080/10407789408955983

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor