Specific heat capacity
The specific heat capacity indicates the ability of a substance to store heat. This substance size corresponds to the amount of heat needed to heat a certain amount of a substance by one Kelvin. It is characteristic of each substance and can be used to identify materials. The unit of measure of specific heat capacity is kilojoules per kilogram times Kelvin [kJ/(kg * K)].
In principle, a distinction is made between the specific heat capacity for the temperature change under constant pressure (cp) and under constant volume (cv). The heat supply under constant pressure simultaneously causes an increase in volume, for which a part of the energy is used up. The distinction is of importance only in the consideration of gases and vapors.
The specific heat capacity of solids is used primarily in the construction industry for the assessment of the behavior of building material. In summer, fabrics with high heat capacity keep the rooms cool for a long time. In winter, they keep the heat in the buildings longer. The heat storage capacity is also the basis for the selection of materials in furnace and heating construction.
The specific heat capacity was initially measured by immersing a heated sample of material in water. After the temperature compensation, the specific heat of the sample was calculated on the basis of the temperature difference between the beginning and the end of the experiment. Since in the formula, the heat capacity of the experimental arrangement had to be considered, the process was somewhat cumbersome.
Linseis’ state-of-the-art meters are based on Differential Scanning Calorimetry (DSC) and Differential Thermal Analysis (DTA). These methods provide highly accurate measurement results in a short time. The measurements can be carried out in wide temperature ranges. As a result, it is additionally possible to determine the temperature dependence of the specific heat capacity.
Applications measuring Cp
Application: Specific Heat of Polyethylene
The Picture shows a Polyethylene standard material in a Heat-Cool-Heat Experiment. There are differents in the first and the second heating curve due to change of crystallinity of the sample.
Application: Graphite polycrystalline
Graphite is an excellent material for checking the performance of a Laser/Xenon Flash Thermal Analyzer. The analyzed material shows a maximum thermal diffusivity around room temperature. The specific heat of the material which can be analyzed by comparative method or by using a DSC / High Temperature DSC shows a significant increase at higher temperatures.