scholarly journals Modeling of Forced Flow-thermal Gradient CVI: Effects of Control Parameters and Processing Schemes on a Densification

2020 ◽  
Author(s):  
Pengfei WANG ◽  
Shengfeng Luo ◽  
Hui ZHANG ◽  
Song ZHANG ◽  
Lili ZHENG
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Pore Structure ◽  
Temperature Control ◽  
Thermal Gradient ◽  
Forced Flow ◽  
Structure Evolution ◽  
Control Parameters ◽  
Porosity Distribution ◽  
Channel Temperature

Abstract A two-channel temperature-control infiltration reactor aiming at fabricating thicker and more uniform composites was designed. Unsteady numerical simulations containing hydrodynamics, mass transfer, heat transfer and pore structure evolution were carried out. By analyzing the effects of concentration, velocity and temperature on the porosity distribution, different densification schemes were proposed and compared. Results show that a preform of thickness 0.04 m and initial porosity 0.8 can be densified to a uniform and compact one with the maximum porosity of 0.1 within 300 hours through the three-step densification scheme. This scheme not only assures a low and uniform porosity over the whole preform but also avoids the huge pumping pressure which may cause the preform cracking.

Research on Heat and Mass Transfer of Flat Grooved Heat Pipes

2015 ◽  
Vol 733 ◽  
pp. 599-602
Author(s):  
Lei Cao ◽  
Guo Chang Zhao ◽  
Li Ping Song ◽  
Tian Dong Lu
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Temperature Control ◽  
Experimental Studies ◽  
Heat Pipes ◽  
Electronic Systems ◽  
Temperature Uniformity ◽  
Flat Surfaces ◽  
Flow And Heat Transfer ◽  
High Degree

Flat grooved heat pipes, which are especially useful in obtaining a high degree of temperature uniformity on flat surfaces, have been successfully used in the temperature control of electronic systems, however, the mechanisms governing the flow and heat transfer of this kind of heat pipes are still under scrutiny as some reported results cannot be reproduced by others or some assumptions have been proven to be unreasonable or ideal. The theoretical and experimental studies on flat grooved heat pipes and introduce work performed on modeling flat grooved heat pipes are reviewed in this paper.

Processing of Cf/SiC Composites through Two-Channel Temperature-Control CVI: I, Modeling

2021 ◽  
Vol 324 ◽  
pp. 198-206
Author(s):  
Peng Fei Wang ◽  
Sheng Feng Luo ◽  
Hui Zhang ◽  
Song Zhang ◽  
Li Li Zheng
Keyword(s):  
Temperature Control ◽  
Ceramic Matrix Composites ◽  
Channel Structure ◽  
Structure Evolution ◽  
Outlet Temperature ◽  
Matrix Composites ◽  
Channel Temperature ◽  
Pass Through ◽  
Sic Composites ◽  
Pump Pressure

A two-channel temperature-control CVI scheme was proposed to fabricate thicker and denser composites. The two-channel structure helps to densify a thick preform, and a precise temperature control will guarantee a low and uniform porosity distribution. Validation simulations containing hydrodynamics, mass transfer, heat transfer and pore structure evolution were first carried out. Modeling results confirm that a two-step densification based on the new scheme can work well: At step I, all gases pass through the preform and the high-temperature bottom-preform is densified; At step II, by altering the outlet, temperature and infiltration time, part of gases are sucked into the preform and the remaining coarse preform is densified. The scheme can fabricate tick, uniform and dense composite, it can also avoid huge pump pressure thus protecting fibers from cracking. It is hoped to enlighten the CVI processing of ceramic matrix composites.

Transport phenomena in MHD mixed convective nanofluid flow

2019 ◽  
Vol 30 (2) ◽  
pp. 769-791
Author(s):  
Prabhugouda Mallanagouda Patil ◽  
Shashikant A. ◽  
Ebrahim Momoniat
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Wall Heat Transfer ◽  
Control Parameters ◽  
Nanofluid Flow ◽  
Content Type ◽  
Transfer Rates

Purpose This study aims to investigate the unsteady magnetohydrodynamic mixed convective nanofluid flow by using Buongiorno two-phase model to achieve an appropriate mechanism to improve the efficiency of solar energy systems by mitigating the energy losses. Design/methodology/approach The transport phenomena occurring in this physical problem are modelled using nonlinear partial differential equations and are non-dimensionalised by using non-similar transformations. The quasilinearisation technique is used to solve the resulting system with the help of a finite difference scheme. Findings The study reveals that the effect of the applied transverse magnetic parameter is to increase the temperature profile and to reduce the wall heat transfer rate. The Brownian diffusion and thermophoresis parameters that characterise the nanofluids contribute to the reduction in wall heat transfer rate. The presence of nanoparticles in the fluid gives rise to critical values for the thermophoresis parameter describing the behaviour of the wall heat and mass transfer rates. Wall heating and cooling are analysed by considering the percentage increase or percentage decrease in the heat and mass transfer rates in the presence of nanoparticles in the fluid. Research limitations/implications The investigation on wall cooling/heating leads to the analysis of control parameters applicable to the industrial design of thermal systems for energy storage, energy harvesting and cooling applications. Practical implications The analysis of the control parameters is of practical value to the solar industry. Social implications In countries, such as South Africa, daily power cuts are a reality. Any research into improving the quality of energy obtained from alternate sources is a national necessity. Originality/value From the literature survey in the present study, it is found that no similar work has been reported in the open literature that analyses the time-dependent mixed convection flow along the exponentially stretching surface in the presence of the effects of a magnetic field, nanoparticles and non-similar solutions.

Unsteady Mixed Convection Near the Stagnation Point in Three-Dimensional Flow

1982 ◽  
Vol 104 (1) ◽  
pp. 132-138 ◽  
Author(s):  
M. Kumari ◽  
G. Nath
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Skin Friction ◽  
Stagnation Point ◽  
Wall Temperature ◽  
Buoyancy Force ◽  
Three Dimensional ◽  
Forced Flow ◽  
Unsteady Mixed Convection ◽  
Similar Solutions

The combined effect of forced and free convection on the unsteady laminar incompressible boundary-layer flow with mass transfer at the stagnation point of a three-dimensional body with time dependent wall temperature has been studied. Both semisimilar and self-similar solutions have been obtained. The governing equations have been solved numerically using an implicit finite-difference scheme. The results indicate that the buoyancy force strongly affects the skin friction whereas its effect on the heat transfer is comparatively less. However, the heat transfer is significantly changed due to the wall temperature which varies with time, but the skin friction is little affected by it. The mass transfer and Prandtl number affect both the skin friction and heat transfer. The buoyancy force which assists the forced flow causes an overshoot in both the velocity components.

3D Thermosolutal Convection within Porous Media

2014 ◽  
Vol 348 ◽  
pp. 27-39 ◽  
Author(s):  
Kacem Amel ◽  
Oueslati Fakhreddine ◽  
Rachid Bennacer ◽  
Elcafsi Afif
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Thermosolutal Convection ◽  
Control Parameters ◽  
Characteristic Parameters ◽  
Convection And Heat Transfer ◽  
Flow Heat ◽  
Vertical Walls ◽  
Left And Right

The present work aims to study convection and heat transfer and mass in a porous cubic cavity. The configuration considered is a cavity cube with vertical walls left and right are subjected to temperatures required while others are impermeable and adiabatic. We realized that the results depend on several characteristic parameters, and general correlations are established for the calculation of heat and mass transfer, according to various studied parameters. The study focuses on the influence of the control parameters on the structure of the flow, heat and mass transfer.

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