Aalborg Universitet Thermophysical Properties of Building Materials Lecture Notes Johra, Hicham Publication date: 2019 Document Version Publisher's PDF, also known as Version of record Link to publication from Aalborg University Citation for published version (APA): Johra, H. (2019). Thermophysical Properties of Building Materials: Lecture Notes. Department of Civil Engineering, Aalborg University. DCE Lecture notes No. 76 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. ? Users may download and print one copy of any publication from the public portal for the purpose of private study or research. ? You may not further distribute the material or use it for any profit-making activity or commercial gain ? You may freely distribute the URL identifying the publication in the public portal ? Take down policy If you believe that this document breaches copyright please contact us at [email protected] providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from vbn.aau.dk on: November 25, 2020 Thermophysical Properties of Building Materials: Lecture Notes Hicham Johra ISSN 1901-7286 DCE Lecture Notes No. 76 Aalborg University Department of Civil Engineering Architectural Engineering DCE Lecture Notes No. 76 Thermophysical Properties of Building Materials: Lecture Notes by Hicham Johra December 2019 © Aalborg University Scientific Publications at the Department of Civil Engineering Technical Reports are published for timely dissemination of research results and scientific work carried out at the Department of Civil Engineering (DCE) at Aalborg University. This medium allows publication of more detailed explanations and results than typically allowed in scientific journals. Technical Memoranda are produced to enable the preliminary dissemination of scientific work by the personnel of the DCE where such release is deemed to be appropriate. Documents of this kind may be incomplete or temporary versions of papers—or part of continuing work. This should be kept in mind when references are given to publications of this kind. Contract Reports are produced to report scientific work carried out under contract. Publications of this kind contain confidential matter and are reserved for the sponsors and the DCE. Therefore, Contract Reports are generally not available for public circulation. Lecture Notes contain material produced by the lecturers at the DCE for educational purposes. This may be scientific notes, lecture books, example problems or manuals for laboratory work, or computer programs developed at the DCE. Theses are monograms or collections of papers published to report the scientific work carried out at the DCE to obtain a degree as either PhD or Doctor of Technology. The thesis is publicly available after the defence of the degree. Latest News is published to enable rapid communication of information about scientific work carried out at the DCE. This includes the status of research projects, developments in the laboratories, information about collaborative work and recent research results. Published 2019 by Aalborg University Department of Civil Engineering Thomas Manns Vej 23 DK-9220 Aalborg Ø, Denmark Printed in Aalborg at Aalborg University ISSN 1901-7286 DCE Lecture Notes No. 76 Contents 1. Foreword ................................................................................................................................................... 6 2. Motivations ................................................................................................................................................ 7 3. Density ....................................................................................................................................................... 9 3.1. Definitions ......................................................................................................................................... 9 3.2. Measuring Density ........................................................................................................................... 10 4. Specific Heat Capacity ............................................................................................................................. 12 4.1. Definitions ....................................................................................................................................... 12 4.2. Measuring Specific Heat Capacity ................................................................................................... 13 5. Volumetric Heat Capacity ........................................................................................................................ 15 6. Thermal Capacity ..................................................................................................................................... 16 6.1. Definitions ....................................................................................................................................... 16 6.2. Thermal Capacity in Simple (Thermodynamic) Terms ..................................................................... 17 6.3. Effects of Thermal Capacity and Thermal Inertia in Buildings ......................................................... 21 7. Thermal Conductivity .............................................................................................................................. 23 7.1. Definitions ....................................................................................................................................... 23 7.2. Effects of Thermal Conductivity in Buildings ................................................................................... 26 7.3. Calculation of Heat Transfer and Thermal Resistance .................................................................... 26 7.4. Measuring Thermal Conductivity .................................................................................................... 30 8. Thermal Diffusivity................................................................................................................................... 34 8.1. Definitions ....................................................................................................................................... 34 8.2. Measuring Thermal Diffusivity ........................................................................................................ 36 9. Some Other Interesting Material Properties for the Building Energy Efficiency and Indoor Environment Quality. ............................................................................................................................................................ 37 References ....................................................................................................................................................... 38 1. Foreword The aim of this lecture note is to introduce the motivations for knowing and measuring the thermophysical properties of materials, and especially construction materials. The main material characteristics regarding thermodynamics are detailed together with some of their respective measurement methods and their implications in building physics. Those thermophysical properties of building materials can be measured at the Building Material Characterization Laboratory of Aalborg University - Department of Civil Engineering [1]. 2. Motivations Good knowledge of the thermophysical properties of materials in general, and construction materials in particular, is crucial for any calculation, modeling and simulation of heat transfer, thermodynamics and temperature distribution in solids, fluids or all sorts, mechanical systems and buildings. Figure 1: Building thermodynamics, heat transfer, and temperature distribution. In thermodynamics, the 3 main properties of the materials in which heat transfer occurs are “Density”, “Specific Heat Capacity” and “Thermal Conductivity”. They are the parameters of the fundamental differential equation of thermodynamics: “The Heat Equation”: × × = ( × ) + (1) Where, ∇ ∙ ∇ : Temperature [K or °C] : Density of the material [kg/m3] : Specific heat capacity of the material [J/kg.K] : Thermal conductivity [W/m.K] : Volumetric heat source [W/m3] : Time [sec] This heat equation can be written in a simpler form by considering only one-dimensional heat transfer and only conductive term (no internal heat source and only heat transfer by conduction): × × = (2) 2 2 Where, : Space coordinate in the 1-dimensional domain [m] Because this heat equation is the basis of all heat transfer, heat losses, temperature distribution and thermodynamics numerical models commonly used in science and engineering to calculate the temperature at a specific point of the space domain at a given time, one can understand the importance of knowing the material properties with accuracy. 3. Density 3.1. Definitions The density (or volumetric mass density) of a material is the amount of mass per unit volume of material. In simple words, for a given volume of material, the higher is the density of material in this volume and the higher is the mass of this volume of material. The density is commonly denoted “ρ” (the lower case Greek letter “rho”), but it is also sometimes denoted “D”. The SI unit of kg/m3 is commonly used for material