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

Matti Kokkala, Djebar Baroudi

Research output: Book/ReportReport


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


  • 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


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