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Title:Molecular dynamic simulation of pool boiling process
Author(s):Borowiec, Katarzyna
Advisor(s):Kozlowski, Tomasz
Contributor(s):Zhang, Yang
Department / Program:Nuclear, Plasma, & Rad Engr
Discipline:Nuclear, Plasma, Radiolgc Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):heat transfer coefficient, molecular dynamics simulation
Abstract:Following work presents molecular dynamic simulation of the pool boiling process of water molecules with heater modelled as lattice of copper atoms. Heat transfer coefficient was calculated, and the results were compared to existing correlations for pool boiling heat transfer. The purpose of the analysis was to test feasibility of molecular dynamics simulation in the study of boiling process. Using approximate potentials, methodology of molecular dynamics simulation applied to boiling process was presented. The results may be improved with the use of more sophisticated description of molecular interactions, increasing domain size and time of the simulation. Due to limitation of the analysis accurate prediction of heat transfer coefficient was not possible. In this work, temperature of the heated surface was controlled variable and the value of heat flux was measured. Simulation was conducted for water at pressure 2.7 bar, which is typical pressure of reflood and passive cooling systems. The bulk of the water was kept at saturation temperature for the entirety of simulation. Temperature of the heated surface was set to achieve desired temperature difference between saturated fluid and wall equal to DT = [10, 20, 30, 40] K. Heater was modelled as copper atoms arranged in the lattice with Morse potential governing the interaction. Potential between water molecules was represented using TIP4P/2005 model [1] and water-copper interaction was set to be Lennard-Jones potential. Simulation was conducted with the use of LAMMPS molecular dynamic simulator [2] [3]. Analysis included investigation of potentials for water by surface tension and liquid - vapor density calculation. Water-copper interaction was parametrized based on contact angle of water droplet on the copper surface. Analysis of pool boiling indicated a significant difference between heat transfer coefficient calculated from simulation and the value calculated form the available correlations. This discrepancy is caused by inaccurate representation of potential between water molecules and the atoms of the copper surface, underlying differences in surface properties and differences in macroscopic and microscopic phenomena. Additionally, analysis was limited in size of the system and time of the simulation, which makes comparison with experimental results not feasible. Nevertheless, presented work gives framework for further study of heat transfer on microscopic level.
Issue Date:2017-12-05
Rights Information:Copyright 2017 Katarzyna Borowiec
Date Available in IDEALS:2018-03-13
Date Deposited:2017-12

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