Thesis supervisor: Tibor Poós
Location of studies (in Hungarian): Department of Building Service and Process Engineering Abbreviation of location of studies: EPGET
Description of the research topic:
a.) Antecedents
In order to achieve optimal design, operation and control for a fluidized bed, it is very important to understand the flow and heat transfer characteristics. In the past physical experiments have been conducted to quantify the heat transfer coefficients (HTC) but these studies were focused mainly on the macroscopic level showing the overall heat transfer behavior. However, for a good design and operation of a fluidized bed dryer, it is necessary to quantify heat transfer mechanisms at particle level, which can be characterized experimentally only to a limited extent. The heat transfer to a particle should be described by at least three mechanisms, convection from fluid, conduction from particles or wall and radiation from the particle to its surrounding enclosed path. These details are difficult to be quantified by measurements. Furthermore, the local gas-solid flow structure will strongly affect the heat transfer of a particle. It is again very difficult to formulate the local flow structures in particle bed.
Publications in international journals and conferences, project works, BSc and MSc theses and the research projects funded by the Hungarian Scientific Research Funds (NKFIH/PD-116326 (2015-2018)).
b.) Aim of the research
The aim of the research is to optimize the time required for drying the solid particles in a fluidized bed by analyzing the particle-particle contact, particle-particle collisions, particle-fluid interactions, local voidage and local gas-solid flow structure. A numerical coupled DEM-CFD model will be developed in which solid particles will be simulated using discrete element method (DEM) and gas flow through CFD and their coupling will enable to elucidate the fundamentals governing the heat transfer in the fluidized bed at a particle level. By varying the local gas-solid flow structure, particle-particle contacts and collisions, particle wall interactions and number of particles, shape and size of particles, changing the bed height, bed flow area and bed temperature the time dependent temperature distribution of the particles will be modeled and then determining the heat transfer coefficients (HTCs) for the particles. In addition, effects of varying superficial gas velocity and gas volume flowrate on the HTCs will be studied for the particles with different thermal conductivities.
c.) Tasks, main items and necessary time
• Study of the previously collected literature and review of new literature in the coupling of DEM-CFD modeling and numerical models to be used (1 semester)
• Performing the laboratory measurements for finding the moisture content, material volumes, particle geometry and operating parameters for determining the performance of the dryer (2 semesters)
• Exploring the relationships between the material characteristics, operating parameters and heat transfer mechanisms, also determining the initial and boundary conditions for the numerical model (1 semester)
• Creation of the numerical model for the equipment, performing calculations for multi-objective optimization and validating the numerical results with measurements (2 semesters)
• Writing the PhD thesis and publishing research articles in scientific journals (2 semesters)
d.) Expected scientific results
• Development of a comprehensive numerical DEM-CFD model for optimizing the drying efficiency and drying time.
• Minimize the heat required for drying process.
• Comparison of different numerical models, which have been used until now.
• Extending the model to a generalized fluidized bed.
• Presenting the optimal operating parameters for the bed and thus achieving a reliable drying operation.
e.) Literature
[1] POÓS, T.; SZABÓ, V.: Volumetric Heat Transfer Coefficient in Fluidized-Bed Dryers, Chemical Engineering & Technology, 41 (3), 2018, DOI: 10.1002/ceat.201700038,
[2] POÓS, T.; SZABÓ, V.: Determination of entry length of a fluidized bed dryer using volumetric heat transfer coefficient, International Review of Applied Sciences and Engineering, 8 (1), 2017, 57-65.
Required language skills: angol Number of students who can be accepted: 1
Deadline for application: 2021-03-23
2024. IV. 17. ODT ülés Az ODT következő ülésére 2024. június 14-én, pénteken 10.00 órakor kerül sor a Semmelweis Egyetem Szenátusi termében (Bp. Üllői út 26. I. emelet).
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