Identification of thermal boundary conditions in heat exchangers of fluidized bed boilers

Ludowski, Paweł; Taler, Dawid; Taler, Jan

doi:10.1016/j.applthermaleng.2013.03.064

Cited by 35 publications

(20 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…A proper understanding of combustion and heat transfer in furnaces and heat exchange on the water-steam side in tubes needs an accurate measurement of heat flux which is taken over by membrane furnace walls [1,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Identification of boundary conditions has also great practical meaning in boiler superheaters [2]. There are three wide categories of heat flux measurements of the boiler water-walls: (1) portable heat flux devices inserted in inspection ports [11][12][13][14][15], (2) Gardon-type heat flux meters welded to the sections of the boiler tubes [11][12][13][14], (3) tubular-type instruments located between two neighboring boiler tubes [1,2,7,8,[16][17][18][19][20][21].…”

Section: Measurements Of Heat Flux Absorbed By Water Walls In Combustmentioning

confidence: 99%

“…There are three wide categories of heat flux measurements of the boiler water-walls: (1) portable heat flux devices inserted in inspection ports [11][12][13][14][15], (2) Gardon-type heat flux meters welded to the sections of the boiler tubes [11][12][13][14], (3) tubular-type instruments located between two neighboring boiler tubes [1,2,7,8,[16][17][18][19][20][21]. Tubular-type and Gardon meters placed on the furnace tube wall in intense slagging areas can be important boiler diagnostic device for monitoring of slag deposition [2,[22][23][24]. If a heat flux instrument is to measure the absorbed heat flux accurately, it must be similar to the boiler tube as closely as possible.…”

Section: Measurements Of Heat Flux Absorbed By Water Walls In Combustmentioning

confidence: 99%

“…Therefore, the measurement of the heat flux absorbed by water-walls with satisfactory accuracy is a challenging task. Considerable work has been done in recent years in this field [1,2,[9][10][11][12][13][14][15][16][17][18][19][20][21]24]. Previous studies to precisely measure the local heat flux to membrane water walls in steam boilers failed due to unknown water-side heat transfer coefficients.…”

Section: Measurements Of Heat Flux Absorbed By Water Walls In Combustmentioning

confidence: 99%

“…Direct and inverse problems in a platen superheater situated in the combustion chamber of a CFB boiler were studied in [2].…”

Section: Identification Of Thermal Boundary Conditions In Heat Exchanmentioning

confidence: 99%

“…The Levenberg-Marquardt method that was used for solving nonlinear least squares problem was also included in the Python program. This chapter is based mainly on two papers published earlier [1,2].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Solving Inverse Heat Transfer Problems When Using CFD Modeling

Ludowski¹,

Taler²,

Taler³

2016

Numerical Simulation - From Brain Imaging to Turbulent Flows

Self Cite

View full text Add to dashboard Cite

The chapter presents solving steady-state inverse heat transfer problems using Computational Fluid Dynamics (CFD) software. Two examples illustrate the application of the proposed method. As the first inverse problem determining the absorbed heat flux to water walls in furnaces of steam boilers is presented in detail. Three different measurement devices (flux tubes) were designed to identify steady-state boundary conditions in water wall tubes of combustion chambers. The first meter is made of a short eccentric tube in which four thermocouples on the fire side below the inner and outer tube surfaces are installed. The fifth thermocouple is situated at the rear of the tube on the housing side of the water wall tube. The second meter has two longitudinal fins that are welded to the bare eccentric tube. In the third option of the instrument, the fins are attached to the water wall tubes but not to the flux tubes as in the second version of the flux tubes. The first instrument is used to measure the heat flux to water walls made from bare tubes, while another two heat flux tubes are designated for measuring the heat flux to membrane walls. Unlike the existing devices, the flux tube is not attached to neighboring water-wall tubes. The absorbed heat flux on the outer surface and the heat transfer coefficient at the inner surface of the flux tube are determined from temperature measurements at internal points. The thermal conductivity of the flux-tube material is a function of temperature. The nonlinear inverse problem of heat conduction (IHCP) is solved using the least-squares method. Three unknown parameters are determined using the Levenberg-Marquardt method. In each iteration, the temperature distribution in the cross section of the heat flux instrument is determined using the ANSYS/CFX software.Another inverse heat transfer problem will be a CFD simulation carried out for the platen superheater placed in the combustion chamber of the circulating fluidized bed (CFB) boiler. Velocity, pressure, and temperature of the steam, as well as the temperature of the tube wall with the complex cross section, were computed using the ANSYS/ CFX software. The direct and inverse problems were solved. In the first inverse problem, the heat transfer coefficient on the flue-gas side was determined based on the meas- ured steam temperature at the inlet and outlet of the three pass steam superheater. In the second inverse problem, the inlet steam temperature and the heat transfer coefficient on the flue-gas side were estimated using measured steam temperatures at selected locations of the superheater. The Levenberg-Marquardt method was also used to solve the second inverse problem. At every iteration step, a direct conjugate heat transfer problem was solved using the ANSYS/CFX software. The CFX program was called and controlled by an external program written in Python language. The LevenbergMarquardt algorithm was also included in the Python program.

show abstract

Section: Measurements Of Heat Flux Absorbed By Water Walls In Combustmentioning

confidence: 99%

Section: Measurements Of Heat Flux Absorbed By Water Walls In Combustmentioning

confidence: 99%

Section: Measurements Of Heat Flux Absorbed By Water Walls In Combustmentioning

confidence: 99%

“…Direct and inverse problems in a platen superheater situated in the combustion chamber of a CFB boiler were studied in [2].…”

Section: Identification Of Thermal Boundary Conditions In Heat Exchanmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Solving Inverse Heat Transfer Problems When Using CFD Modeling

Ludowski¹,

Taler²,

Taler³

2016

Numerical Simulation - From Brain Imaging to Turbulent Flows

Self Cite

View full text Add to dashboard Cite

show abstract

Inverse identification of viscosity coefficient for Newtonian and non‐Newtonian slurries during the turbulent pipeline transportation

Zhang

Yuan

Cheng

et al. 2019

Asia-Pacific J Chem Eng

View full text Add to dashboard Cite

Slurry viscosity is an important parameter that can be used for slurry characterization and pipeline design. This study proposed an inversion method to identify the viscosity coefficient of slurries in turbulent pipeline flow. An inverse heat convection problem with unknown viscosity for Newtonian and non‐Newtonian slurries was solved in a fully developed turbulent pipe flow, and a modified mixing length theory in the turbulent model was applied to improve the estimation accuracy. Through the inversion calculation, the viscosity coefficient was obtained by temperature profile at several measurement positions. An experimental setup was established, and several experiments were conducted to verify the viscosity estimations for slurry flow in this study. The results showed that the method was reliable for identifying the slurry viscosities in the turbulent state and the modified mixing length model can effectively improve the inversion accuracy. This method provided an effective way to detect the rheological properties for determining the operation mode of turbulent slurry pipelines.

show abstract

Creep rupture life assessment of superheater tube with oxide formation in power plant

Jing

et al. 2020

Materials & Corrosion

View full text Add to dashboard Cite

This paper proposes a method for predicting the creep rupture life of superheater tubes, considering the continuous increasing metal temperature and stress as a result of oxide formation. The steam-side oxide growth was assessed by the parabolic oxidation rate law, and the temperature profiles of superheater tubes was calculated combining the 3D computational fluid dynamics simulation and the 1D analytical models. Based on the estimated temperature and maximum elastic hoop stress, the parametric extrapolation technique was utilized to assess the creep rupture life. The validity of this method was confirmed by measuring the oxide thickness and the steam temperature in the field. The results found that T91 alloy in the steam outlet region and T23 alloy at the connection point was susceptible to creep rupture failure, which had the greatest cumulative damage and thickest oxide scale. The cumulative damage of superheater tubes varied significantly with tube count. Results suggested that replacement of the particular T91 alloy tubing section having the minimum creep rupture life with a better heat-resistant steel would avoid mechanical failure by creep for the subject boiler system.

show abstract

Identification of thermal boundary conditions in heat exchangers of fluidized bed boilers

Cited by 35 publications

References 12 publications

Solving Inverse Heat Transfer Problems When Using CFD Modeling

Solving Inverse Heat Transfer Problems When Using CFD Modeling

Inverse identification of viscosity coefficient for Newtonian and non‐Newtonian slurries during the turbulent pipeline transportation

Creep rupture life assessment of superheater tube with oxide formation in power plant

Contact Info

Product

Resources

About