APPLICATIONS OF THE TEMPERATURE STEP METHOD FOR DETERMINING THE SPECIFIC HEAT CAPACITY OF BUILDING MATERIALS

Abstract

Properties of building materials include many properties, the most important are mechanical, thermal, chemical, and economic. The most important thermal properties that characterize the total heat losses and thermal inertia of materials are thermal conductivity and specific heat capacity. The first one describes the stationary heat transfer through the structures, but the second describes the ability to absorb and release the heat energy with temperature change dynamically, and it is related to a unit mass of the specimen. The specific heat capacity can be measured directly using differential scanning calorimetry (DSC), the most common method of thermal analysis. DSC method uses the heat flow principle and homogeneous heating. Sensors with high sensitivity, short time periods and a small-sized chamber guarantee high detection sensitivity and stable, reproducible results. There are two main disadvantages which prevents these approaches from being widely used in the field of building physics � relatively small sample dimension and high equipment costs. Sample size limitation is very critical in the case of non-homogeneous building products. A so-called temperature step method is being studied as an alternative approach for quick and cheap measurements of the heat capacity for building materials. Principle used in such measurements is a rapid temperature increase in a closed large-sized insulated chamber with the dynamic analysis of generated thermal information considering the thermal mass of the plates. In general, this method is based on measuring the heat amount required to heat a sample with known mass from one quasi-stationary temperature equilibrium state to another in an insulated chamber with calibrated heat losses. This approach has been tested on several heterogeneous building materials, including samples with phase change materials with subsequent calculations of latent heat, showing good accuracy compared to the DSC method, as well as reducing the required measurement time. The use of this approach will make it easier and cheaper to determine the unknown or assumed only theoretically heat capacity property of building materials.