A Numerical Investigation on the Influence of Porosity on the Steady-State and Transient Thermal–Hydraulic Behavior of the PBMR

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Masoumeh Sadat Latifi ◽  
Saeed Setayeshi ◽  
Giuseppe Starace ◽  
Maria Fiorentino
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Effective Thermal Conductivity ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Heat Removal ◽  
Coolant Temperature ◽  
Pebble Bed ◽  
Transient Conditions ◽  
Decay Heat

The thermal–hydraulic phenomena in a pebble bed modular reactor (PBMR) core have been simulated under steady-state and transient conditions. The PBMR core is basically a long right circular cylinder with a fuel effective height of 11 m and a diameter of 3.7 m. It contains approximately 452,000 fuel pebbles. A three-dimensional computational fluid dynamic (CFD) model of the PBMR core has been developed to study the influence of porosity on the core performance after reactor shutdown. The developed model was carried out on a personal computer using ANSYS fluent 14.5. Several important heat transfer and fluid flow parameters have been examined under steady-state and transient conditions, including the coolant temperature, effective thermal conductivity of the pebble bed, and the decay heat. Porosity was found to have a significant influence on the coolant temperature, on the effective thermal conductivity of the pebble bed, on the decay heat, and on the required time for heat removal.

Steady-State Investigation of Vapor Deposited Micro Heat Pipe Arrays

1995 ◽  
Vol 117 (1) ◽  
pp. 75-81 ◽  
Author(s):  
A. K. Mallik ◽  
G. P. Peterson
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Surface Temperature ◽  
Heat Pipe ◽  
Effective Thermal Conductivity ◽  
Heat Pipes ◽  
Temperature Gradients ◽  
Bottom Surface ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

An experimental investigation of vapor deposited micro heat pipe arrays was conducted using arrays of 34 and 66 micro heat pipes occupying 0.75 and 1.45 percent of the cross-sectional area, respectively. The performance of wafers containing the arrays was compared with that of a plain silicon wafer. All of the wafers had 8 × 8 mm thermofoil heaters located on the bottom surface to simulate the active devices in an actual application. The temperature distributions across the wafers were obtained using a Hughes Probeye TVS Infrared Thermal Imaging System and a standard VHS video recorder. For wafers containing arrays of 34 vapor deposited micro heat pipes, the steady-state experimental data indicated a reduction in the maximum surface temperature and temperature gradients of 24.4 and 27.4 percent, respectively, coupled with an improvement in the effective thermal conductivity of 41.7 percent. For wafers containing arrays of 66 vapor deposited micro heat pipes, the corresponding reductions in the surface temperature and temperature gradients were 29.0 and 41.7 percent, respectively, and the effective thermal conductivity increased 47.1 percent, for input heat fluxes of 4.70 W/cm2. The experimental results were compared with the results of a previously developed numerical model, which was shown to predict the temperature distribution with a high degree of accuracy, for wafers both with and without the heat pipe arrays.

Inverse Determination of Temperature-Dependent Thermal Conductivity Using Steady Surface Data on Arbitrary Objects

2000 ◽  
Vol 122 (3) ◽  
pp. 450-459 ◽  
Author(s):  
T. J. Martin ◽  
G. S. Dulikravich
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Steady State ◽  
Measurement Errors ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Computational Procedure ◽  
Heat Fluxes ◽  
Computational Method ◽  
Transfer Coefficients

An inverse computational method has been developed for the nonintrusive and nondestructive evaluation of the temperature-dependence of thermal conductivity. The methodology is based on an inverse computational procedure that can be used in conjunction with an experiment. Given steady-state heat flux measurements or convection heat transfer coefficients on the surface of the specimen, in addition to a finite number of steady-state surface temperature measurements, the algorithm can predict the variation of thermal conductivity over the entire range of measured temperatures. Thus, this method requires only one temperature probe and one heat flux probe. The thermal conductivity dependence on temperature (k-T curve) can be completely arbitrary, although a priori knowledge of the general form of the k-T curve substantially improves the accuracy of the algorithm. The influence of errors of measured surface temperatures and heat fluxes on the predicted thermal conductivity has been evaluated. It was found that measurement errors of temperature up to five percent standard deviation were not magnified by this inverse procedure, while the effect of errors in measured heat fluxes were even lower. The method is applicable to two-dimensional and three-dimensional solids of arbitrary shape and size. [S0022-1481(00)01703-5]

Fabrication of thermally conductive and electrically insulating polymer composites with isotropic thermal conductivity by constructing a three-dimensional interconnected network

Nanoscale ◽  
2019 ◽  
Vol 11 (23) ◽  
pp. 11360-11368 ◽  
Author(s):  
Hao Yuan ◽  
Yang Wang ◽  
Ting Li ◽  
Yijie Wang ◽  
Piming Ma ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Polymer Composites ◽  
Thermal Management ◽  
Three Dimensional ◽  
Heat Removal ◽  
Interconnected Network ◽  
Microelectronic Devices ◽  
Thermally Conductive

Efficient heat removal via thermal management materials has become one of the most critical challenges in the development of modern microelectronic devices.

Numerical Simulation of Heat and Mass Transfer in Metal Hydride Hydrogen Accumulators of Different Complex Designs

2010 ◽  
Author(s):  
Dmitriy Lazarev ◽  
Valeriy Artemov ◽  
Georgiy Yankov ◽  
Konstantin Minko
Keyword(s):  
Thermal Conductivity ◽  
Mass Transfer ◽  
Effective Thermal Conductivity ◽  
Heat And Mass Transfer ◽  
Metal Hydride ◽  
Solid Phase ◽  
Three Dimensional ◽  
Calculated Data ◽  
Sorption Rate ◽  
Gas Admixtures

A three-dimensional mathematical model of unsteady heat and mass transfer in porous hydrogen-absorbing media, accounting for presence of “passive” gas admixtures, is developed. New technique for evaluation of effective thermal conductivity of porous medium, which consists of microparticles, is suggested. Effect of “passive” gas admixtures on heat and mass transfer and sorption rate in metal hydride reactor is analyzed. It is shown that decrease of effective thermal conductivity and partial hydrogen pressure under decrease of hydrogen concentration effect on the hydrogen sorption rate considerably. It is disclosed that an intensive 3D natural convection takes place in a gas volume of reactor under certain conditions. Numerical analysis of heat and mass transfer in metal-hydride reactor of hydrogen accumulation systems was done. Sorption of hydrogen in cylindrical reactors with external cooling and central supply of hydrogen are analyzed including reactors with finned active volume and tube-shell reactor with external and internal cooling cartridge matrix. Unsteady three dimensional temperature and concentration fields in solid phase are presented. Integral curves representing the dynamic of sorption and desorption are calculated. Data on efficiency of considered reactors are presented and compared.

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