Modelling particulate fouling in heat exchanger with high solid content liquid suspension: Dissertation

Research output: ThesisDissertationMonograph

Abstract

A computational fluid dynamics (CFD) model for particulate fouling in high solid content heat exchangers has been developed. The model is applicable in practical industrial heat exchangers. Particulate fouling is generally considered as a serial process of transport of particles into the vicinity of the wall, adherence on the surface and possible reentrainment from the surface. The CFD fouling model was first implemented as a detailed two fluid Eulerian model, which included all the relevant near-wall forces affecting on the colloidal particles and requiring an extremely fine mesh near the fouling surface. For modelling particle transport, the generally accepted models were applied. Particle adhesion on the surface was described by a mass transfer coefficient based on the XDLVO theory. Based on the experience gained from the detailed model, a wall function approach was developed for calculating the near-wall particle transport in order to avoid the use of excessively small computational cells. The wall function model was compared to a detailed CFD model and to experimental results from a fouling test apparatus. Deposition of sub-micron calcium carbonate (CaCO3) particles on a heated stainless steel AISI 316L surface in water based suspension was used as a case study. Comparisons were made with several heat fluxes and mass flow rates applying two different high particle concentrations. As a practical case, the wall function approach was applied in the modelling of industrial corrugated heat exchanger equipment with liquid of very high particle content. For including the non-Newtonian viscosity behaviour of the high solid content slurry, the model for viscosity was derived from the experiments. The re-entrainment of the particles from the surface takes place, if the hydrodynamic forces exceed the adhesion forces even temporarily. Shear stress is a dominant force affecting the re-entrainment. For evaluating the shear strass in detail, the test apparatus was modelled using large eddy simulation (LES) method in addition to the standard k- turbulence model. The re-entrainment model presented in the literature was applied in order to evaluate the effect of surface roughness and surface energy on the re-entrainment. The model was modified for CFD application, and it was applied in fouling modelling of the practical heat exchanger. The effect of surface roughness on adhesion was studied based on the models presented in literature. In addition, the effect of particle size distribution on the fouling rate was examined.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Lampinen, Markku, Supervisor, External person
  • Manninen, Mikko, Supervisor
Award date21 May 2015
Place of PublicationEspoo
Publisher
Print ISBNs978-951-38-8250-1
Electronic ISBNs978-951-38-8251-8
Publication statusPublished - 2015
MoE publication typeG4 Doctoral dissertation (monograph)

Fingerprint

Fouling
Heat exchangers
Liquids
Wall function
Computational fluid dynamics
Adhesion
Dynamic models
Surface roughness
Viscosity
Large eddy simulation
Calcium carbonate
Turbulence models
Interfacial energy
Particle size analysis
Heat flux
Shear stress
Mass transfer
Stainless steel
Hydrodynamics
Flow rate

Keywords

  • CFD
  • particulate
  • fouling
  • heat exchanger

Cite this

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title = "Modelling particulate fouling in heat exchanger with high solid content liquid suspension: Dissertation",
abstract = "A computational fluid dynamics (CFD) model for particulate fouling in high solid content heat exchangers has been developed. The model is applicable in practical industrial heat exchangers. Particulate fouling is generally considered as a serial process of transport of particles into the vicinity of the wall, adherence on the surface and possible reentrainment from the surface. The CFD fouling model was first implemented as a detailed two fluid Eulerian model, which included all the relevant near-wall forces affecting on the colloidal particles and requiring an extremely fine mesh near the fouling surface. For modelling particle transport, the generally accepted models were applied. Particle adhesion on the surface was described by a mass transfer coefficient based on the XDLVO theory. Based on the experience gained from the detailed model, a wall function approach was developed for calculating the near-wall particle transport in order to avoid the use of excessively small computational cells. The wall function model was compared to a detailed CFD model and to experimental results from a fouling test apparatus. Deposition of sub-micron calcium carbonate (CaCO3) particles on a heated stainless steel AISI 316L surface in water based suspension was used as a case study. Comparisons were made with several heat fluxes and mass flow rates applying two different high particle concentrations. As a practical case, the wall function approach was applied in the modelling of industrial corrugated heat exchanger equipment with liquid of very high particle content. For including the non-Newtonian viscosity behaviour of the high solid content slurry, the model for viscosity was derived from the experiments. The re-entrainment of the particles from the surface takes place, if the hydrodynamic forces exceed the adhesion forces even temporarily. Shear stress is a dominant force affecting the re-entrainment. For evaluating the shear strass in detail, the test apparatus was modelled using large eddy simulation (LES) method in addition to the standard k- turbulence model. The re-entrainment model presented in the literature was applied in order to evaluate the effect of surface roughness and surface energy on the re-entrainment. The model was modified for CFD application, and it was applied in fouling modelling of the practical heat exchanger. The effect of surface roughness on adhesion was studied based on the models presented in literature. In addition, the effect of particle size distribution on the fouling rate was examined.",
keywords = "CFD, particulate, fouling, heat exchanger",
author = "Ulla Ojaniemi",
note = "BA3124",
year = "2015",
language = "English",
isbn = "978-951-38-8250-1",
series = "VTT Science",
publisher = "VTT Technical Research Centre of Finland",
number = "88",
address = "Finland",
school = "Aalto University",

}

Modelling particulate fouling in heat exchanger with high solid content liquid suspension : Dissertation. / Ojaniemi, Ulla.

Espoo : VTT Technical Research Centre of Finland, 2015. 117 p.

Research output: ThesisDissertationMonograph

TY - THES

T1 - Modelling particulate fouling in heat exchanger with high solid content liquid suspension

T2 - Dissertation

AU - Ojaniemi, Ulla

N1 - BA3124

PY - 2015

Y1 - 2015

N2 - A computational fluid dynamics (CFD) model for particulate fouling in high solid content heat exchangers has been developed. The model is applicable in practical industrial heat exchangers. Particulate fouling is generally considered as a serial process of transport of particles into the vicinity of the wall, adherence on the surface and possible reentrainment from the surface. The CFD fouling model was first implemented as a detailed two fluid Eulerian model, which included all the relevant near-wall forces affecting on the colloidal particles and requiring an extremely fine mesh near the fouling surface. For modelling particle transport, the generally accepted models were applied. Particle adhesion on the surface was described by a mass transfer coefficient based on the XDLVO theory. Based on the experience gained from the detailed model, a wall function approach was developed for calculating the near-wall particle transport in order to avoid the use of excessively small computational cells. The wall function model was compared to a detailed CFD model and to experimental results from a fouling test apparatus. Deposition of sub-micron calcium carbonate (CaCO3) particles on a heated stainless steel AISI 316L surface in water based suspension was used as a case study. Comparisons were made with several heat fluxes and mass flow rates applying two different high particle concentrations. As a practical case, the wall function approach was applied in the modelling of industrial corrugated heat exchanger equipment with liquid of very high particle content. For including the non-Newtonian viscosity behaviour of the high solid content slurry, the model for viscosity was derived from the experiments. The re-entrainment of the particles from the surface takes place, if the hydrodynamic forces exceed the adhesion forces even temporarily. Shear stress is a dominant force affecting the re-entrainment. For evaluating the shear strass in detail, the test apparatus was modelled using large eddy simulation (LES) method in addition to the standard k- turbulence model. The re-entrainment model presented in the literature was applied in order to evaluate the effect of surface roughness and surface energy on the re-entrainment. The model was modified for CFD application, and it was applied in fouling modelling of the practical heat exchanger. The effect of surface roughness on adhesion was studied based on the models presented in literature. In addition, the effect of particle size distribution on the fouling rate was examined.

AB - A computational fluid dynamics (CFD) model for particulate fouling in high solid content heat exchangers has been developed. The model is applicable in practical industrial heat exchangers. Particulate fouling is generally considered as a serial process of transport of particles into the vicinity of the wall, adherence on the surface and possible reentrainment from the surface. The CFD fouling model was first implemented as a detailed two fluid Eulerian model, which included all the relevant near-wall forces affecting on the colloidal particles and requiring an extremely fine mesh near the fouling surface. For modelling particle transport, the generally accepted models were applied. Particle adhesion on the surface was described by a mass transfer coefficient based on the XDLVO theory. Based on the experience gained from the detailed model, a wall function approach was developed for calculating the near-wall particle transport in order to avoid the use of excessively small computational cells. The wall function model was compared to a detailed CFD model and to experimental results from a fouling test apparatus. Deposition of sub-micron calcium carbonate (CaCO3) particles on a heated stainless steel AISI 316L surface in water based suspension was used as a case study. Comparisons were made with several heat fluxes and mass flow rates applying two different high particle concentrations. As a practical case, the wall function approach was applied in the modelling of industrial corrugated heat exchanger equipment with liquid of very high particle content. For including the non-Newtonian viscosity behaviour of the high solid content slurry, the model for viscosity was derived from the experiments. The re-entrainment of the particles from the surface takes place, if the hydrodynamic forces exceed the adhesion forces even temporarily. Shear stress is a dominant force affecting the re-entrainment. For evaluating the shear strass in detail, the test apparatus was modelled using large eddy simulation (LES) method in addition to the standard k- turbulence model. The re-entrainment model presented in the literature was applied in order to evaluate the effect of surface roughness and surface energy on the re-entrainment. The model was modified for CFD application, and it was applied in fouling modelling of the practical heat exchanger. The effect of surface roughness on adhesion was studied based on the models presented in literature. In addition, the effect of particle size distribution on the fouling rate was examined.

KW - CFD

KW - particulate

KW - fouling

KW - heat exchanger

M3 - Dissertation

SN - 978-951-38-8250-1

T3 - VTT Science

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -