Boundary Optimal Control of Natural Convection by Means of Mode Reduction

2000 ◽  
Vol 124 (1) ◽  
pp. 47-54 ◽  
Author(s):  
H. M. Park ◽  
W. J. Lee
Keyword(s):  
Optimal Control ◽  
Heat Flux ◽  
Natural Convection ◽  
Gradient Method ◽  
Flux Distribution ◽  
Boussinesq Equation ◽  
Heat Flux Distribution ◽  
Projected Gradient Method ◽  
Galerkin Procedure ◽  
Low Dimensional

We consider problems of controlling the intensity of the Rayleigh-Be´nard convection by adjusting the heat flux distribution at the boundary while keeping the heat input the same. The Karhunen-Loe`ve Galerkin procedure is used to reduce the Boussinesq equation to a low dimensional dynamic model, which in turn is employed in a projected gradient method to yield the optimal heat flux distribution. The performance of the Karhunen-Loe`ve Galerkin procedure is assessed in comparison with the traditional technique employing the Boussinesq equation, and is found to be very accurate as well as efficient.

Natural Convection of Non-Newtonian Fluids About a Horizontal Surface in a Porous Medium

1987 ◽  
Vol 109 (3) ◽  
pp. 119-123 ◽  
Author(s):  
H. T. Chen ◽  
C. K. Chen
Keyword(s):  
Heat Flux ◽  
Porous Medium ◽  
Natural Convection ◽  
Power Law ◽  
Flux Distribution ◽  
Similarity Solutions ◽  
Iteration Scheme ◽  
Heat Flux Distribution ◽  
Runge Kutta Method ◽  
Power Law Index

The problem of natural convection of a non-Newtonian power-law fluid about a horizontal impermeable surface in the porous medium is considered, where the plate is assumed with a nonuniform heat flux distribution. The present study is based on the boundary layer approximation and only suitable for a high Rayleigh number. Similarity solutions are obtained by using the fourth-order Runge-Kutta method and the Nachtsheim-Swigert iteration scheme. The effects of the nonuniform wall heat flux qw(x) and the new power-law index n on the heat transfer characteristics are discussed.

The Effect of Droplet Impingement on Pressure and Heat Flux Distributions on Molten Pool in GMAW-Based Rapid Forming

2014 ◽  
Vol 494-495 ◽  
pp. 391-394
Author(s):  
Feng Liang Yin ◽  
Sheng Zhu ◽  
Jian Liu ◽  
Xiao Ming Wang ◽  
Lei Guo
Keyword(s):  
Heat Flux ◽  
Numerical Model ◽  
Molten Pool ◽  
Flux Distribution ◽  
Three Dimensional ◽  
Heat Flux Distribution ◽  
Droplet Impingement ◽  
Dimensional Precision ◽  
Low Dimensional

A low dimensional precision is one of drawback for the GMAW-based rapid forming technique, which is related to pressure and heat flux on molten pool. To study pressure and heat flux on molten pool, the effect of droplet impinging process must been considered. A three-dimensional numerical model was built to analysis pressure and heat flux distribution on molten pool. Solving the model, it was found that pressure on the cathode by the arc decreases dramatically when the droplet is coming. As to heat flux, the appearance of droplet cuts down it within about 1.5 mm away from arc axial. Out of 1.5 mm away from arc axial, droplets effect on heat flux is not obvious.

Heat Flux Distribution Over a Solar Central Receiver Using an Aiming Strategy Based on a Conventional Closed Control Loop

2017 ◽  
Author(s):  
Jesús García ◽  
Yen Chean Soo Too ◽  
Ricardo Vasquez Padilla ◽  
Rodrigo Barraza Vicencio ◽  
Andrew Beath ◽  
...  
Keyword(s):  
Heat Flux ◽  
Flux Distribution ◽  
Thermal Stresses ◽  
Control Strategies ◽  
Multiple Input Multiple Output ◽  
Control Loop ◽  
Heat Flux Distribution ◽  
Input Multiple Output ◽  
Solar Receiver ◽  
Solar Field

Solar thermal towers are a maturing technology that have the potential to supply a significant part of energy requirements of the future. One of the issues that needs careful attention is the heat flux distribution over the central receiver’s surface. It is imperative to maintain receiver’s thermal stresses below the material limits. Therefore, an adequate aiming strategy for each mirror is crucial. Due to the large number of mirrors present in a solar field, most aiming strategies work using a data base that establishes an aiming point for each mirror depending on the relative position of the sun and heat flux models. This paper proposes a multiple-input multiple-output (MIMO) closed control loop based on a methodology that allows using conventional control strategies such as those based on Proportional Integral Derivative (PID) controllers. Results indicate that even this basic control loop can successfully distribute heat flux on the solar receiver.

Studies on heat flux distribution on the membrane walls in a 600 MW supercritical arch-fired boiler

2016 ◽  
Vol 103 ◽  
pp. 264-273 ◽  
Author(s):  
Dalong Zhang ◽  
Chenwei Meng ◽  
Hai Zhang ◽  
Pengyuan Liu ◽  
Zhouhang Li ◽  
...  
Keyword(s):  
Heat Flux ◽  
Flux Distribution ◽  
Heat Flux Distribution

Research on Heat Flux Distribution in Deep Grinding

2008 ◽  
Author(s):  
D. H. Zhu ◽  
B. Z. Li ◽  
J. G. Yang
Keyword(s):  
Heat Flux ◽  
Flux Distribution ◽  
Theoretical Expression ◽  
Uniform Heat Flux ◽  
Heat Transfer Mechanism ◽  
Heat Flux Distribution ◽  
Workpiece Surface ◽  
Quadratic Curve ◽  
Flux Model ◽  
Heat Flux Model

This paper studies the heat transfer mechanism in deep grinding process, especially the heat flux to the workpiece. On the basis of triangle moving heat source, a quadratic curve heat flux model in the grinding zone was developed to determine the heat flux distribution and to estimate the surface temperature of workpiece. From the calculated theoretical expression of heat flux to the workpiece, the quadratic curve heat flux can be understood as the superposition of square law heat flux, triangular heat flux and uniform heat flux in the grinding zone. Then four heat flux models using the determined amount of heat flux were applied to estimate the workpiece surface temperatures which were compared with that measured by the embedded thermocouple. It has been found that the quadratic curve heat flux distribution seems to give the best match with measured and theoretical temperature, although square law heat flux model is good enough to predict the temperature.

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