scholarly journals Estimation of feedwater heater parameters based on a grey-box approach

2011 ◽  
Vol 21 (4) ◽  
pp. 703-715 ◽  
Author(s):  
Tomasz Barszcz ◽  
Piotr Czop
Keyword(s):  
Parameter Estimation ◽  
Measurement Data ◽  
Physical Parameters ◽  
Model Parameters ◽  
First Principle ◽  
Transfer Coefficients ◽  
Component Library ◽  
Matlab Simulink ◽  
Heat Transfer Coefficients ◽  
Diagnostic Applications

Estimation of feedwater heater parameters based on a grey-box approachThe first-principle modeling of a feedwater heater operating in a coal-fired power unit is presented, along with a theoretical discussion concerning its structural simplifications, parameter estimation, and dynamical validation. The model is a part of the component library of modeling environments, called the Virtual Power Plant (VPP). The main purpose of the VPP is simulation of power generation installations intended for early warning diagnostic applications. The model was developed in the Matlab/Simulink package. There are two common problems associated with the modeling of dynamic systems. If an analytical model is chosen, it is very costly to determine all model parameters and that often prevents this approach from being used. If a data model is chosen, one does not have a clear interpretation of the model parameters. The paper uses the so-called grey-box approach, which combines first-principle and data-driven models. The model is represented by nonlinear state-space equations with geometrical and physical parameters deduced from the available documentation of a feedwater heater, as well as adjustable phenomenological parameters (i.e., heat transfer coefficients) that are estimated from measurement data. The paper presents the background of the method, its implementation in the Matlab/Simulink environment, the results of parameter estimation, and a discussion concerning the accuracy of the method.

Design of an axially concave pad profile for a large turbine tilting-pad bearing

2016 ◽  
Vol 231 (4) ◽  
pp. 479-488 ◽  
Author(s):  
Sebastian Kukla ◽  
Nico Buchhorn ◽  
Beate Bender
Keyword(s):  
Heat Transfer ◽  
Film Thickness ◽  
Load Capacity ◽  
Measurement Data ◽  
Tangential Direction ◽  
Measured Temperature ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Tilting Pad ◽  
Calculation Results

To improve operational safety and/or achieve a higher load capacity of turbine tilting-pad bearings, an axially concave pad profile is presented. The thermal and mechanical stress of the loaded pads of a test bearing in load between pivot configuration has been analysed. Both film thickness and pressure distribution have been measured at a very high resolution. A fluid film calculation program in combination with a finite-volume-based structural mechanics program is used to simulate the deformation of a single pad under high circumferential speeds. In this context, the axial and tangential heat transfer coefficients of the pad surface, which act as boundary conditions for the calculation of the 3D temperature distribution, are determined using an optimization process. Herein, the match of predicted and measured pad temperatures is the goal. It can be shown that there must be a huge difference in heat transfer in axial and tangential direction in order to match the large measured temperature gradient in circumferential direction. Based on the measured deformed profile the program code is used to derive a concave pad profile, which will result in an axially non-arched sliding surface under the expected thermal load. Therefore, an iterative simulation procedure is used. By decreasing the axial arching of the pad and thus the large film thickness at the axial ends using an improved profile designed for a specific operation point, the minimum film thickness and maximum pad temperature can be influenced beneficially. The comparison of measurement data and calculation results shows very good agreement regarding the pad deformations. The results indicate that by axially concave profiling of the loaded pads of a large tilting-pad bearing for a specific operation point, the static characteristics in the form of temperature, film thickness and load capacity can be improved.

An Application of Extended Kalman Filtering to Heat Exchanger Models

1994 ◽  
Vol 116 (2) ◽  
pp. 257-264 ◽  
Author(s):  
G. Jonsson ◽  
O. P. Palsson
Keyword(s):  
Kalman Filter ◽  
Heat Exchanger ◽  
Extended Kalman Filter ◽  
Working Conditions ◽  
Space Form ◽  
Model Parameters ◽  
Transfer Coefficients ◽  
Extended Kalman Filtering ◽  
Heat Transfer Coefficients ◽  
Empirical Relations

This paper shows how an extended Kalman filter can be applied to the parameter estimation in continuous time heat exchanger models. The model is based on lumping of the heat exchanger. It is on state space form where the temperature in each section is a model state. By letting the model parameters be functions of the massflows and the temperatures one obtains a model that is capable of accurately describing the dynamics of the heat exchanger for all relevant working conditions. Since the parameters are functions of temperature, the model is nonlinear in the states and an extended Kalman filter is applied to the state estimation. Empirical relations of the heat transfer coefficients are incorporated in the model parameters in order to cope with the massflow and temperature dependence. Some of the parameters in the empirical relations are also estimated, thereby adjusting the formulas to the specific heat exchanger.

scholarly journals Bayesian Parameter Estimation of Convective Heat Transfer Coefficients of a Roof-Mounted Radiant Barrier System

2005 ◽  
Vol 128 (2) ◽  
pp. 213-225 ◽  
Author(s):  
Philippe Lauret ◽  
Frédéric Miranville ◽  
Harry Boyer ◽  
François Garde ◽  
Laetitia Adelard
Keyword(s):  
Heat Transfer ◽  
Parameter Estimation ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Bayesian Methods ◽  
Thermal Model ◽  
Estimation Method ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

This paper deals with the application of Bayesian methods to the estimation of two convective heat-transfer coefficients of a roof-mounted radiant barrier system. As part of an empirical validation of the thermal model of the roofing complex, a parametric sensitivity analysis highlighted the importance of convective coefficients in the thermal behavior of a roofing complex. A parameter estimation method is then used in order to find the values of the coefficients that lead to an improvement of the thermal model. However, instead of using a classical parameter estimation method, we used a Bayesian inference approach to parameter estimation. The aim of the paper is to introduce the basic concepts of this powerful method in this simple two-parameter case. We show that Bayesian methods introduce an explicit treatment of uncertainty in modeling and a corresponding measure of reliability for the conclusions reached.

scholarly journals Review on the Surface Heat Transfer Coefficients of Radiant Systems

2019 ◽  
Vol 111 ◽  
pp. 01075 ◽  
Author(s):  
Jun Shinoda ◽  
Ongun B. Kazanci ◽  
Shin-ichi Tanabe ◽  
Bjarne W. Olesen
Keyword(s):  
Heat Transfer ◽  
Heated Surface ◽  
Measurement Data ◽  
Radiant Heat ◽  
Surface Measurement ◽  
Radiant Heat Transfer ◽  
Extensive Literature ◽  
Prediction Errors ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Heat transfer coefficients are often used to describe the thermal behaviour of radiant systems and how it transfers heat between the cooled/heated surface and the room. In addition to current standards, numerous studies have been conducted to obtain the heat transfer coefficients through experiments and simulations. However, inconsistency is evident in the values or expressions suggested. Thus, this study investigated possible sources of discrepancy through an extensive literature review on articles and standards that focused on the heat transfer coefficients at the cooled/heated surface. Measurement data provided by different authors were extracted to compare both the amount of heat transfer and the actual heat transfer coefficients. Consequently, suggested values and expressions were used to predict the measurement data in other articles to examine their accuracy. Comparison of the results showed that the radiant heat transfer coefficients had a consistent value throughout the literature and had prediction error within ±20%. However, larger deviations and prediction errors were seen in the total and convective heat transfer. It was suggested that some of the sources of error may have been the calculation procedure of each heat transfer mechanism, choice of reference temperature and its measurement height/position, and room dimensions.

Inverse Determination of Steady Heat Convection Coefficient Distributions

1998 ◽  
Vol 120 (2) ◽  
pp. 328-334 ◽  
Author(s):  
T. J. Martin ◽  
G. S. Dulikravich
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Boundary Conditions ◽  
Measurement Data ◽  
Cost Effective ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Simple Modification ◽  
Heat Transfer Coefficients ◽  
Thermal Boundary Conditions

An inverse Boundary Element Method (BEM) procedure has been used to determine unknown heat transfer coefficients on surfaces of arbitrarily shaped solids. The procedure is noniterative and cost effective, involving only a simple modification to any existing steady-state heat conduction BEM algorithm. Its main advantage is that this method does not require any knowledge of, or solution to, the fluid flow field. Thermal boundary conditions can be prescribed on only part of the boundary of the solid object, while the heat transfer coefficients on boundaries exposed to a moving fluid can be partially or entirely unknown. Over-specified boundary conditions or internal temperature measurements on other, more accessible boundaries are required in order to compensate for the unknown conditions. An ill-conditioned matrix results from the inverse BEM formulation, which must be properly inverted to obtain the solution to the ill-posed problem. Accuracy of numerical results has been demonstrated for several steady two-dimensional heat conduction problems including sensitivity of the algorithm to errors in the measurement data of surface temperatures and heat fluxes.

Investigation of thermal performance of single basin solar still with soft drink cans filled with sand as a storage medium

2021 ◽  
pp. 1-31
Author(s):  
A.M. Khallaf ◽  
A.A. El-Sebaii ◽  
M.M. Hegazy
Keyword(s):  
Mathematical Model ◽  
Thermal Performance ◽  
Soft Drink ◽  
Model Parameters ◽  
Solar Still ◽  
Storage Material ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Basin Water ◽  
The Masses

Abstract Thermal performance of the single basin solar still (SBSS) with and without a storage material is presented experimentally and theoretically. New configuration of the SBSS by using soft drink cans filled with sand, fixed on the upper surface of the basin liner, as a sensible storage material is investigated. A mathematical model (using Pascal language) is developed to verify the thermal performance of the SBSS. Comparisons between experimental and theoretical (obtained from the mathematical model) results are carried out for validating the proposed mathematical model. Parameters affecting the thermal performance of the SBSS such as the masses of the basin water and storage material, heat transfer coefficients and top losses are investigated. The top losses (Ut) for the SBSS with sand is lower than that without sand by about 27.47%. The daily productivity (Pd) and efficiency (ηd) of the SBSS with sand is more than that without sand by about 31.44 and 23.12%, respectively. This experiment is environmentally friendly by using 126 of the used empty soft drink cans.

Heat Transfer Coefficients and Dynamical Thermal Models for Variable Flow Rates in Pipes and Ducts

2013 ◽  
Vol 291-294 ◽  
pp. 1760-1771
Author(s):  
Bjørn R Sørensen
Keyword(s):  
Heat Transfer ◽  
Heat Loss ◽  
Dynamic Performance ◽  
Measurement Data ◽  
Transfer Coefficients ◽  
Flow Rates ◽  
Variable Flow ◽  
Thermal Models ◽  
Heat Transfer Coefficients ◽  
Ventilation Ducts

This study presents thermal models of pipes or ventilation ducts with variable flow rates. The models are based on dynamic thermodynamic heat balances, and much attention has been put into developing accurate heat transfer coefficients. MATLAB/Simulink environment has been used for modeling, but the model is however universal and can be implemented into any software. The model has been validated against measurement data, and found to be quite accurate for use in typical HVAC applications. Accuracy is particularly good if taking thermal damping into account. Thermal damping of pipe or duct mass has shown to be significant for dynamic performance. The model is suited for control simulations or accurate heat loss simulations, where dynamic conditions are important.

scholarly journals Semi-physical nonlinear circuit model with device/physical parameters for HEMTs

2011 ◽  
Vol 3 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Hiroshi Otsuka ◽  
Toshiyuki Oishi ◽  
Koji Yamanaka ◽  
Mattias Thorsell ◽  
Kristoffer Andersson ◽  
...  
Keyword(s):  
Computer Aided Design ◽  
Measurement Data ◽  
Circuit Model ◽  
Physical Parameters ◽  
Model Parameters ◽  
High Electron ◽  
Large Signal ◽  
Nonlinear Circuit ◽  
Voltage Range ◽  
Gan Hemts

A nonlinear circuit model (NCM) with physical parameters is proposed for direct simulation of the RF characteristics of GaN high-electron-mobility transistors (GaN HEMTs) on the basis of device structure. The physical equations are used for the construction of the model in order to connect strongly the model parameters with the device/physical parameters. Hyperbolic tangent functions are used as the model equations to ensure good model convergence and rapid simulation (short simulation time). The usefulness of these equations is confirmed by technology computer aided design (TCAD) simulation. The number of model parameters for the nonlinear components (Ids, Cgs, Cgd) is reduced to 17 by using common physical parameters for modeling the drain current and capacitance. The accuracy of this model is verified by applying to GaN HEMTs. The modeled I–V and capacitance characteristics agree well with the measurement data over a wide voltage range. Furthermore, this model can be used for the accurate evaluation of S-parameters and large-signal RF characteristics.

scholarly journals Jeffrey Fluid Behaviour on Oscillatory Couette Flow past Two Horizontal Parallel Plates in Presence of MHD and Radioactive Heat Transfer

2019 ◽  
Vol 8 (11) ◽  
pp. 3252-3257
Keyword(s):  
Heat Transfer ◽  
Finite Difference ◽  
Couette Flow ◽  
Jeffrey Fluid ◽  
Physical Parameters ◽  
Parallel Plates ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Fluid Behaviour ◽  
Non Linear System

The aim of this study carry out on an unsteady MHD at no cost convective oscillatory Couette flow of a wellknown non-Newtonian Jeffrey fluid of an optically thin fluid bounded by two horizontal porous parallel walls in a channel embedded in porous medium in the presence of thermal radiation and angle of inclination. Design and Method is the flow is governed by a coupled non-linear system of partial differential equations which are solved numerically by using finite difference method. Results are the impacts of various physical parameters on the flow quantities viz. velocity and temperature reports, skinfriction and rate of heat transfer coefficients are studied numerically. The results are discussed with the help of graphs and tables. Conclusion is the finite difference results are compared favourably with already established results in literatures.

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