![Sample our Engineering & Technology journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5933/TOC-Subject-Sample-2021-Engineering-Tech.jpg"})
ABSTRACT
The fouling layers on heat exchanger surfaces exhibit complicated structures, which essentially affect flow hydrodynamics, fouling kinetics, and hence the heat transfer performance. Numerical models developed so far for the fouling process, however, are based exclusively on the assumption of an impermeable fouling layer with a uniform porous structure. In order to quantitatively evaluate the effect of fouling layer structure on fouling dynamics, this work systematically investigated four representative schemes for fouling layer characterization: a homogeneous porous medium that is impermeable to water (HoIm), a heterogeneous porous medium that is impermeable to water (HeIm), a homogeneous porous medium that is permeable to water (HoPe), and a heterogeneous porous medium that is permeable to water (HePe). Under the same operational conditions, four models offer significantly different prediction results on the fluid velocity, temperature distribution, and fouling resistance. It is concluded that numerical model development should take the fouling layer structure into account, and the scheme of HePe that best resembles a real fouling layer structure should be a promising option.
Nomenclature
| Cf | = | friction coefficient, dimensionless |
| Cp | = | specific heat capacity, J/(kg-K) |
| HeIm | = | heterogeneous porous medium that is impermeable to water |
| HoIm | = | homogeneous porous medium that is impermeable to water |
| HePe | = | heterogeneous porous medium that is permeable to water |
| HoPe | = | homogeneous porous medium that is permeable to water |
| = | unit vector | |
| k | = | permeability of the porous medium, m2 |
| p | = | pressure, Pa |
| Δp | = | pressure drop, Pa |
| q | = | heat flux, kW/m2 |
| Rf | = | fouling resistance, m2-K/W |
| s | = | area, m2 |
| SEM | = | scanning electron microscope |
| T | = | temperature, K |
| = | velocity vector, m/s | |
| vin | = | inlet velocity magnitude, m/s |
| x | = | x coordinate in a Cartesian coordinate system |
Greek symbols
| λ | = | thermal conductivity, W/(m-K) |
| μ | = | viscosity of the fluid, Pa-s |
| ρ | = | density, kg/m3 |
| ω | = | porosity of the fouling layer, dimensionless |
| Ωe | = | solution domain |
| Ωf | = | fouling layer domain |
| Ωh | = | substrate domain |
| ∂Ωe-f | = | solution–fouling layer interface, that is, free–porous media flow interface |
| ∂Ωh-f | = | substrate–fouling layer interface |
Subscripts
| 0 | = | initial clean state (without fouling) |
| e | = | solution |
| eq | = | equivalent |
| f | = | fouling |
| h | = | substrate |
| in | = | inlet |
| r | = | reference state |
| s | = | fouling layer solid |
| w | = | fluid |
Superscripts
| 0 | = | initial clean state (without fouling) |
| — | = | average value |
Funding
This work was supported by the Faculty Start-up Funds from Soochow University, and research funds from the “Jiangsu Specially-Appointed Professors Program,” “Jiangsu Innovation and Entrepreneurship (ShuangChuang) Program,” National Natural Science Foundation of China (number 21406148), Natural Science Foundation of Jiangsu Province (No. BK20130293), and the “Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions.” We also appreciate constructive comments and suggestions from our colleague, Prof. Ruben Mercade-Prieto.
Additional information
Notes on contributors
Jie Xiao
Jie Xiao is a Jiangsu Professor, deputy head of the School of Chemical and Environmental Engineering at Soochow University, Suzhou, China. He received his B.S. degree in industrial automation (2001) and M.S. degree in control science and engineering (2004) from Zhejiang University, Hangzhou, China. In 2010, he received his Ph.D. degree in chemical engineering from Wayne State University, Detroit, MI. Before joining Soochow University, he was a postdoctoral research associate at Washington State University for 2 years. His research field is multiscale systems science and engineering with applied studies in heat exchanger fouling and cleaning, spray drying systems, functional coatings, sustainable manufacturing, and bio-inspired chemical engineering.
Jian Han
Jian Han is a postgraduate (M.S.) student in the School of Chemical and Environmental Engineering at Soochow University, Suzhou, China, under the supervision of Prof. Jie Xiao. In 2013, he received a bachelor's degree in materials science and engineering from Soochow University. He is currently developing predictive models for the induction stage of crystallization fouling.
Feng Zhang
Feng Zhang is an engineer at Bosch Automotive Products (Suzhou), China. He received a B.S. degree in polymer materials and engineering (2012) from Yantai University, Yantai, China. In 2015, he received his M.S. degree in chemical engineering from Soochow University, Suzhou, China. He worked on numerical modeling of crystallization fouling when he was a student at Soochow University.
Xiao Dong Chen
Xiao Dong Chen received his B.E. degree in engineering mechanics from Tsinghua University (1987). He received his Ph.D. in chemical and process engineering from Canterbury University in New Zealand (1991). In January 2013, he began his role as the University Distinguished Professor and Head of School at Soochow University (Suzhou, P.R. China). He established a new School of Chemical and Environmental Engineering there. His main areas of research are in bio-inspired chemical engineering, food engineering and biotechnology, separation processes including drying and membrane processing, heat transfer and mass transfer including fouling, cleaning, and drying, safety processes including spontaneous combustion of solid materials, and powder technology and powder functionality, including food and pharmaceutical particulates.