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Numerical Simulation Study (numerical + simulation_study)

Distribution by Scientific Domains

Engineering	50%

Selected Abstracts

Experimental and Numerical Simulation Study of Heat Transfer Due to Confined Impinging Circular Jet

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 10 2007
L. Chang-geng
Abstract An experimental and numerical simulation study of heat transfer due to a confined impinging circular jet is presented. In this research, a stainless steel foil heated disk was used as the heat transfer surface of a simulated chip, and the thermocouples were mounted symmetrically along the diameter of the foil to measure the temperature distribution on the surface. Driven by a small pump, a circular air jet (1.5,mm and 1,mm in diameter) impinged on the heat-transfer surface with middle and low Reynolds numbers. The parameters, such as Reynolds number and ratio of height-to-diameter, were changed to investigate the radial distribution of the Nusselt number and the characteristics of heat transfer in the stagnation region. Numerical computations were performed by using several different turbulence models. In wall bounded turbulent flows, near-wall modeling is crucial. Therefore, the turbulence models enhanced wall treatment, such as the RNG ,-, model, may be superior for modeling impingement flows. The numerical results showed reasonable agreement with the experimental data for local heat transfer coefficient distributions. The impinging jet may be an effective method to solve the cooling problem of high power density electronic packaging. [source]

Convergence properties of bias-eliminating algorithms for errors-in-variables identification

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 9 2005
Torsten Söderström
Abstract This paper considers the problem of dynamic errors-in-variables identification. Convergence properties of the previously proposed bias-eliminating algorithms are investigated. An error dynamic equation for the bias-eliminating parameter estimates is derived. It is shown that the convergence of the bias-eliminating algorithms is basically determined by the eigenvalue of largest magnitude of a system matrix in the estimation error dynamic equation. When this system matrix has all its eigenvalues well inside the unit circle, the bias-eliminating algorithms can converge fast. In order to avoid possible divergence of the iteration-type bias-eliminating algorithms in the case of high noise, the bias-eliminating problem is re-formulated as a minimization problem associated with a concentrated loss function. A variable projection algorithm is proposed to efficiently solve the resulting minimization problem. A numerical simulation study is conducted to demonstrate the theoretical analysis. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Computational energy analysis of an innovative isothermal chamber for testing of the special equipment used in the transport of perishable products

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2004
S. K. Chatzidakis
Abstract This paper describes an improved numerical simulation study of an isothermal chamber recently constructed at Zografou Campus of the National Technical University of Athens (NTUA) for the testing of special equipment used for transporting perishable foodstuffs in accordance with the United Nations ATP agreement. Using a transient finite difference model, a simulation is developed for a modern ATP test chamber and a typical specimen refrigerated vehicle to be tested. The simulation results are compared to experimental measurements taken under real conditions by a data acquisition system and a refrigerated semi-trailer as specimen. Proportional,integral control is employed for the regulation of the cooling and heating system. The impact of various parameters on the time required to reach the set-point temperature (tset) is investigated and the energy consumption is simulated for a period of 22 h. In particular, the impact of specimen insulation thickness and the thickness of the chamber insulation floor are considered in detail. The total energy consumption increases by approximately 16% when the concrete floor layer thickness is increased from 8 to 16 cm for typical initial conditions and desired chamber and specimen temperatures of 32.5 and 7.5°C, respectively. Using a floor insulation of 6 cm extruded heavy strain-resistant polystyrene reduces the energy consumption by at least 13%. Specimen insulation thickness increase from U -value of 0.35 W m,2 K to 0.75 W m,2 K result to an increase in energy consumption by a percentage of 28%. Thermal capacity, temperature of car body and specimen dimensions are also treated as variables that affect the total duration of an ATP test and its total energy consumption. Copyright © 2004 John Wiley & Sons, Ltd. [source]