A transient symmetrical method for the measurement of temperature dependent thermal diffusivity

Matti Kokkala, Djebar Baroudi

Research output: Book/ReportReport

Abstract

Determination of temperature dependent thermal diffusivities using a transient symmetrical method was studied. The thermal diffusivity is determined from the temperature profile in a specimen constructed of thin slabs and heated symmetrically from both sides. The thermal diffusivity is determined as the ratio of the time derivate and the second spatial derivate at the position of the extremum of temperature. A numerical method was developed to calculate the thermal diffusivity as a function of time including the confidence interval of the diffusivity. The numerical methods were validated by using numerically calculated temperature profiles for a material with known thermal diffusivity. Preliminary tests were conducted to investigate the practical applicability of the method. The method proved to work for an inert material when no changes of geometry of the sample occurred. If reactions, convection, or substantial thermal expansions causing gaps inside the specimen occur, the results will not be well-defined.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages26
ISBN (Print)951-38-4345-9
Publication statusPublished - 1993
MoE publication typeNot Eligible

Publication series

SeriesVTT Tiedotteita - Meddelanden - Research Notes
Number1452
ISSN1235-0605

Fingerprint

thermal diffusivity
temperature profiles
temperature
range (extremes)
diffusivity
confidence
thermal expansion
slabs
convection
intervals
geometry

Keywords

  • fire safety
  • temperature
  • measurement
  • thermal diffusivity
  • thermophysical properties
  • heat transfer
  • calculations
  • utilization
  • experimentations
  • numerical analysis
  • test methods
  • transiet analysis
  • time
  • mineral wool
  • calcium silicates
  • insulating boards
  • geometry

Cite this

Kokkala, M., & Baroudi, D. (1993). A transient symmetrical method for the measurement of temperature dependent thermal diffusivity. Espoo: VTT Technical Research Centre of Finland. VTT Tiedotteita - Meddelanden - Research Notes, No. 1452
Kokkala, Matti ; Baroudi, Djebar. / A transient symmetrical method for the measurement of temperature dependent thermal diffusivity. Espoo : VTT Technical Research Centre of Finland, 1993. 26 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 1452).
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Kokkala, M & Baroudi, D 1993, A transient symmetrical method for the measurement of temperature dependent thermal diffusivity. VTT Tiedotteita - Meddelanden - Research Notes, no. 1452, VTT Technical Research Centre of Finland, Espoo.

A transient symmetrical method for the measurement of temperature dependent thermal diffusivity. / Kokkala, Matti; Baroudi, Djebar.

Espoo : VTT Technical Research Centre of Finland, 1993. 26 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 1452).

Research output: Book/ReportReport

TY - BOOK

T1 - A transient symmetrical method for the measurement of temperature dependent thermal diffusivity

AU - Kokkala, Matti

AU - Baroudi, Djebar

PY - 1993

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N2 - Determination of temperature dependent thermal diffusivities using a transient symmetrical method was studied. The thermal diffusivity is determined from the temperature profile in a specimen constructed of thin slabs and heated symmetrically from both sides. The thermal diffusivity is determined as the ratio of the time derivate and the second spatial derivate at the position of the extremum of temperature. A numerical method was developed to calculate the thermal diffusivity as a function of time including the confidence interval of the diffusivity. The numerical methods were validated by using numerically calculated temperature profiles for a material with known thermal diffusivity. Preliminary tests were conducted to investigate the practical applicability of the method. The method proved to work for an inert material when no changes of geometry of the sample occurred. If reactions, convection, or substantial thermal expansions causing gaps inside the specimen occur, the results will not be well-defined.

AB - Determination of temperature dependent thermal diffusivities using a transient symmetrical method was studied. The thermal diffusivity is determined from the temperature profile in a specimen constructed of thin slabs and heated symmetrically from both sides. The thermal diffusivity is determined as the ratio of the time derivate and the second spatial derivate at the position of the extremum of temperature. A numerical method was developed to calculate the thermal diffusivity as a function of time including the confidence interval of the diffusivity. The numerical methods were validated by using numerically calculated temperature profiles for a material with known thermal diffusivity. Preliminary tests were conducted to investigate the practical applicability of the method. The method proved to work for an inert material when no changes of geometry of the sample occurred. If reactions, convection, or substantial thermal expansions causing gaps inside the specimen occur, the results will not be well-defined.

KW - fire safety

KW - temperature

KW - measurement

KW - thermal diffusivity

KW - thermophysical properties

KW - heat transfer

KW - calculations

KW - utilization

KW - experimentations

KW - numerical analysis

KW - test methods

KW - transiet analysis

KW - time

KW - mineral wool

KW - calcium silicates

KW - insulating boards

KW - geometry

M3 - Report

SN - 951-38-4345-9

T3 - VTT Tiedotteita - Meddelanden - Research Notes

BT - A transient symmetrical method for the measurement of temperature dependent thermal diffusivity

PB - VTT Technical Research Centre of Finland

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ER -

Kokkala M, Baroudi D. A transient symmetrical method for the measurement of temperature dependent thermal diffusivity. Espoo: VTT Technical Research Centre of Finland, 1993. 26 p. (VTT Tiedotteita - Meddelanden - Research Notes; No. 1452).