Conjugate Heat Transfer in Stratified Two-Fluid Flows with a Growing Deposit Layer

The article presents a numerical model for moving boundary conjugate heat transfer in stratified two-fluid flows with a growing deposit layer. The model is applicable to other general moving boundary conjugate heat transfer problem in a two-fluid flow environment with deposition occurring simultaneously. The level-set method is adopted to capture the fluid-fluid interface and fluid-deposit interface. The governing equations are solved using a finite volume method. Upon verification of the model, the effects of inlet velocity ratio, Damköhler number and thermal conductivity ratio on the flow, deposition as well as heat transfer are investigated. Generally, Nusselt number on the lower wall (with a growing deposit layer), Nulx and upper wall, Nuux show distinct features with the change of these parameters. Nuux increases with the increase of lower fluid layer (fluid 1) inlet velocity and the thermal conductivity of deposit layer while it decreases with the increase of Damkholer number. Nulx varies differently in the upstream and the downstream of the channel. A higher lower fluid layer (fluid 1) velocity and a higher thermal conductivity of deposit layer result in a higher Nulx upstream but a lower Nulx downstream. However, a higher Damkholer number results in a lower Nulx upstream and a higher Nulx downstream

Numerical investigation of conjugated heat transfer in a channel with a moving depositing front

This article presents numerical simulations of conjugated heat transfer in a fouled channel with a moving depositing front. The depositing front separating the fluid and the deposit layer is captured using the level-set method. Fluid flow is modeled by the incompressible Navier–Stokes equations. Numerical solution is performed on a fixed mesh using the finite volume method. The effects of Reynolds number and thermal conductivity ratio between the deposit layer and the fluid on local Nusselt number as well as length-averaged Nusselt number are investigated. It is found that heat transfer performance, represented by the local and length-averaged Nusselt number reduces significantly in a fouled channel compared with that in a clean channel. Heat transfer performance decreases with the growth of the deposit layer. Increases in Reynolds, Prandtl numbers both enhance heat transfer. Besides, heat transfer is enhanced when the thermal conductivity ratio between the deposit layer and the fluid is lower than 20 but it decreases when the thermal conductivity ratio is larger than 2

Face Detection in Intelligent Ambiences with Colored Illumination

Human face detection is an essential step in the creation of intelligent lighting ambiences, but the constantly changing multi-color illumination makes reliable face detection more challenging. Therefore, we introduce a new face detection and localization algorithm, which retains a high performance under various indoor illumination conditions. The method is based on the creation of a robust skin mask, using general color constancy techniques, and the application of the Viola-Jones face detector on the candidate face areas. Extensive experiments, using a challenging state-of-the-art database and a new one with a wider variation in colored illumination and cluttered background, show a significantly better performance for the newly proposed algorithm than for the most widely used face detection algorithms

The impact of innovation management techniques on product innovation performance: An empirical study

New product development (NPD) is a great challenge for manufacturers. However, empirical research on the impact of innovation management techniques (IMT) on innovation performance is seldom reported. An industrial survey is therefore conducted to verify the perceived usefulness of 41 IMT and their impact on innovation performance in Hong Kong electronics and electrical appliances industry. After 153 out of 527 manufacturers were surveyed and their data analyzed, the results show that 39 IMT are positively related to new product performance. However, only 8 out of them are positively related to new products in the product categories, whereas only 10 related to sales due to new products. The findings of this study give insights on the implementation of IMT to improve firm performance. © 2010 IEEE

Numerical and experimental study of forced convection in graphite foams of different configurations

Forced convection heat transfer in a channel with different configurations of graphite foams is experimentally and numerically studied in this paper. The physical properties of graphite foams such as the porosity, pore diameter, density, permeability and Forchheimer coefficient are determined experimentally. The local temperatures at the surface of the heat source and the pressure drops across different configurations of graphite foams are measured. In the numerical simulations, the Navier–Stokes and Brinkman–Forchheimer equations are used to model the fluid flow in the open and porous regions, respectively. The local thermal non-equilibrium model is adopted in the energy equations to evaluate the solid and fluid temperatures. Comparisons are made between the experimental and simulation results. The results showed that the solid block foam has the best heat transfer performance at the expense of high pressure drop. However, the proposed configurations can achieve relatively good enhancement of heat transfer at moderate pressure drop

Analysis of effects of active sources on observed phase velocity based on the thin layer method

10.1016/j.jappgeo.2010.11.005Journal of Applied Geophysics73149-5

Transient behavior of fluid flow and heat transfer with phase change in vertical porous channels

The transient behavior of flow boiling in vertical porous channels is numerically studied in this paper. The velocity and temperature fields under different parameters for both aiding and opposing flows are investigated. Distinctly different flow and heat transfer features are observed in the comparison of aiding and opposing flows. An analysis of liquid saturation along the heated wall indicates that the minimum liquid saturation for aiding flow is located at the tail of the heated section, whereas for opposing flow, it is within the heated section and shifts upstream with the increase of Rayleigh number and decrease of Peclet number

Analysis of fluid flow and heat transfer in a channel with staggered porous blocks

Fluid flow and heat transfer characteristics in a channel with staggered porous blocks were numerically studied in this paper. The Navier–Stokes and Brinkman–Forchheimer equations were used to model the fluid flow in the open and porous regions, respectively. Coupling of the pressure and velocity fields was resolved using the SIMPLER algorithm. The local thermal equilibrium model was adopted in the energy equation to evaluate the solid and fluid temperatures. The effect of Darcy number, Reynolds number, porous block height and width on the velocity field were studied. In addition, the effects of the above parameters as well as the thermal conductivity ratio between the porous blocks and the fluid on the local heat transfer were analyzed. The pressure drops across the channel for different cases were discussed. The results show that the flow behavior and its associated local heat transfer are sensitive to the variation of the above parameters. It is predicted by the present study that an increase in the thermal conductivity ratio between the porous blocks and the fluid results in significant enhancement of heat transfer at the locations of the porous blocks

Three-dimensional numerical simulation of fluid flow with phase change heat transfer in an asymmetrically heated porous channel

Fluid flow with phase change heat transfer in a three-dimensional porous channel with asymmetrically heating from one side is numerically studied in this paper. The “modified” Kirchhoff method is used to deal with the spatial discontinuity in the thermal diffusion coefficient in the energy equation. The velocity and temperature fields, as well as the liquid saturation field on the heated section of the wall with different Peclet and Rayleigh numbers are investigated. The results show that the liquid flow bypasses the two-phase zone, while the vapor flows primarily to the interface between the sub-cooled liquid zone and the two-phase zone. An increase in the Peclet number decreases the two-phase region while an increase in the Rayleigh number helps to spread the heat to a larger region of the domain. The distribution of the liquid saturation on the heated section of the wall indicates that the minimum liquid saturation increases with the increase of both the Peclet and Rayleigh number