ISO INTERNATIONAL 21901 STANDARD First edition 2021-02 Thermal insulation Test method for thermal diffusivity Periodic heat method Isolation thermique-Méthode d'essai pour la diffusivité thermique Méthodedechauffagepériodique Referencenumber IS0 21901:2021(E) ISO @ IS0 2021 IS0 21901:2021(E) COPYRIGHTPROTECTEDDOCUMENT IS02021 All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting below or Iso's member body in the country of the requester. ISO copyright office CP 40i : Ch.de Blandonnet 8 CH-1214 Vernier, Geneva Phone: +41 22 749 01 11 Email: copyright@iso.org Website: www.iso.org Published in Switzerland i IS0 2021-All rights reserved IS0 21901:2021(E) Contents Page Foreword ..iv 1 Scope ..1 2 Normative references ..1 Terms and definitions ..1 3 4 Symbols .2 5 Principle. .3 5.1 General .3 5.2 Calculation of thermal diffusivity .3 Test specimen 6 ..6 6.1 Sample .6 6.2 Details of test specimen .6 6.3 Machining of test specimen .6 6.3.1 When using two test specimens .6 .1 6.3.2 When using a single test specimen 7 Apparatus .8 7.1 General. .8 7.2 Temperaturemeasurementinstrument ..9 8 Procedure. .9 8.1 Rounding numbers .9 ..9 8.2 Period oftemperature change 8.3 Amplitudeoftemperaturechange .10 8.4 Measurementmethod 10 8.5 Calculationofthermal diffusivity .11 8.6 Calculation ofthermal conductivity .11 9 Test report ..11 Annex A (normative)Size oftest specimen andperiod oftemperaturechange ..12 AnnexB (informative)Measurement considerations ..15 Bibliography .16 @ IS0 2021 - All rights reserved iii