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Title: Transient Heating and Thermomechanical Stress Modeling of Ceramic HEPA Filters

Abstract

The purpose of this report is to showcase an initial finite-element analysis model of a ceramic High-Efficiency Particulate (HEPA) Air filter design. Next generation HEPA filter assemblies are being developed at LLNL to withstand high-temperature fire scenarios by use of ceramics and advanced materials. The filters are meant for use in radiological and nuclear facilities, and are required to survive 500°C fires over an hour duration. During such conditions, however, collecting data under varying parameters can be challenging; therefore, a Finite Element Analysis model of the filter was conducted using COMSOL ® Multiphysics to analyze the effects of fire. Finite Element Analysis (FEA) modelling offers several opportunities: researchers can quickly and easily consider impacts of potential design changes, material selection, and flow characterization on filter performance. Specifically, this model provides stress references for the sealant at high temperatures. Modeling of full filter assemblies was deemed inefficient given the computational requirements, so a section of three tubes from the assembly was modeled. The model looked at the transient heating and thermomechanical stress development during a 500°C air flow at 6 CFM. Significant stresses were found at the ceramic-metal interfaces of the filter, and conservative temperature profiles at locations of interest weremore » plotted. The model can be used for the development of sealants that minimize stresses at the ceramic-metal interface. Further work on the model would include the full filter assembly and consider heat losses to make more accurate predictions.« less

Authors:
 [1];  [1];  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Workforce Development for Teachers and Scientists (WDTS) (SC-27). Science Undergraduate Laboratory Internship (SULI) Program; USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1410056
Report Number(s):
LLNL-TR-740309
DOE Contract Number:
AC52-07NA27344
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Bogle, Brandon, Kelly, James, and Haslam, Jeffrey. Transient Heating and Thermomechanical Stress Modeling of Ceramic HEPA Filters. United States: N. p., 2017. Web. doi:10.2172/1410056.
Bogle, Brandon, Kelly, James, & Haslam, Jeffrey. Transient Heating and Thermomechanical Stress Modeling of Ceramic HEPA Filters. United States. doi:10.2172/1410056.
Bogle, Brandon, Kelly, James, and Haslam, Jeffrey. 2017. "Transient Heating and Thermomechanical Stress Modeling of Ceramic HEPA Filters". United States. doi:10.2172/1410056. https://www.osti.gov/servlets/purl/1410056.
@article{osti_1410056,
title = {Transient Heating and Thermomechanical Stress Modeling of Ceramic HEPA Filters},
author = {Bogle, Brandon and Kelly, James and Haslam, Jeffrey},
abstractNote = {The purpose of this report is to showcase an initial finite-element analysis model of a ceramic High-Efficiency Particulate (HEPA) Air filter design. Next generation HEPA filter assemblies are being developed at LLNL to withstand high-temperature fire scenarios by use of ceramics and advanced materials. The filters are meant for use in radiological and nuclear facilities, and are required to survive 500°C fires over an hour duration. During such conditions, however, collecting data under varying parameters can be challenging; therefore, a Finite Element Analysis model of the filter was conducted using COMSOL ® Multiphysics to analyze the effects of fire. Finite Element Analysis (FEA) modelling offers several opportunities: researchers can quickly and easily consider impacts of potential design changes, material selection, and flow characterization on filter performance. Specifically, this model provides stress references for the sealant at high temperatures. Modeling of full filter assemblies was deemed inefficient given the computational requirements, so a section of three tubes from the assembly was modeled. The model looked at the transient heating and thermomechanical stress development during a 500°C air flow at 6 CFM. Significant stresses were found at the ceramic-metal interfaces of the filter, and conservative temperature profiles at locations of interest were plotted. The model can be used for the development of sealants that minimize stresses at the ceramic-metal interface. Further work on the model would include the full filter assembly and consider heat losses to make more accurate predictions.},
doi = {10.2172/1410056},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2017,
month = 9
}

Technical Report:

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  • An experimental program is described that will determine the response of 0.6-x 0.6-m (24-x 24-in.) high-efficiency particulate air (HEPA) filters to tornado-induced pressure transients. A blow-down system will be used to impose pressure differentials across the filters. Progress in construction of this system is reported with a description of the component parts and their functions. The test facility is essentially complete with the exception of an air dryer system that has not yet been delivered. Initial structural testing will begin in March 1977. A description is given of the instrumentation needed to measure air pressure, velocity, turbulence, humidity and particulatemore » concentration. This instrumentation includes pressure transducers, humidity equipment, laser Doppler velocimeters (LDV), signal processors and a data acquisition system. Operational theory of the LDV and its proposed use as a particle counting device are described.« less
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  • The temperature and stress and distributions generated in ceramic materials currently employed in microwave gyrotron tube windows were determined for a variety of operating conditions. Both edge- and face-cooled windows of either polycrystalline BeO or polycrystalline Al/sub 2/O/sub 3/ were considered. The actual analysis involved three steps. First, a computer program was used to determine the electric field distribution within the window at a given power level and frequency (TE/sub 02/ wave propagation assumed). This program was capable of describing both the radial and axial dependence of the electric field. The effects of multiple internal reflections at the various dielectricmore » interfaces were also accounted for. Secondly, the field distribution was used to derive an expression for the heat generated per unit volume per unit time within the window due to dieletric losses. A generalized heat conduction computer code was then used to compute the temperature distribution based on the heat generation function. Third, the stresses were determined from the temperature profiles using analytical expression or a finite-element computer program. Steady-state temperature and stress profiles were computed for the face-cooled and edge-cooled windows.« less
  • Four by six-inch transversely anisotropic plates of 1/8 and 1/4 inch thick pyrolytic graphite were subjected to transient heating in an oxyacetylene ilame apparatus. At temperatures up to 1500 deg F, the temperature and thermal strain distributions were determined over the length and thickness of the plates. The thermal strains measured with an optical gage and the analytically determined strains calculated from the three-dimensional thermoelasticity equations for a two-dimensional temperature distribution were found to be in good agreement. The calculated stress distribution indicates that maximum compressive stresses of -- 1400 psi and --3000 psi were produced in the 1/8 inchmore » and 1/4-inch pyrolytic graphite plates, respectively. (auth)« less