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Energy systems: integration, distribution and storage
Published in John Twidell, Renewable Energy Resources, 2021
Materials that change phase offer a much larger heat capacity, over a limited temperature range, than systems using sensible heat. For example, Glauber's salt (Na2SO4.10H2O) has been used as a store for room heating. It decomposes at 32°C to a saturated solution of Na2SO4 plus an anhydrous residue of Na2SO4. This reaction is reversible and evolves 250 kJ/kg ∼650 MJ/m3. Since much of the cost of a store for house heating is associated with the construction, such stores may be cheaper overall than simple water tanks of less energy density per unit volume. Nevertheless, this seemingly simple method requires practical difficulties to be overcome. In particular, the solid and liquid phases often eventually separate spatially so that recombination is prevented; consequently, without mixing, the system becomes inefficient after many cycles.
Introduction to Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
Specific heat capacity of a substance is the amount of heat required to raise the temperature of the unit mass of the substance by 1°C. Latent heat is the quantity of heat evolved or absorbed to change the state of a unit mass of a substance without any change in its temperature.
Material Characterizations
Published in Debasish Sarkar, Nanostructured Ceramics, 2018
Heat capacity is the amount of heat required to raise one kelvin temperature of a material, unit is J/K. It is not normalized. Thus, specific heat capacity defines the amount of heat required to raise one kelvin temperature of one gram material, unit is J/g.K, and designated as Cp. Crystalline material has more ordered atomic structure, and, thus, less molecular motion results in lower specific heat compared to amorphous material. This can be quantified from DSC plot, and their change provide information about phase change. As DSC analysis is performing under constant pressure and uniform heating rate, the specific heat capacity and enthalpy can be related as: () Cp≡(∂H∂T)P
2-D FEM thermomechanical coupling in the analysis of a flexible eRoad subjected to thermal and traffic loading
Published in Road Materials and Pavement Design, 2023
Talita De Freitas Alves, Thomas Gabet, Rosângela Motta
Assuming that there is no heat sources and sinks, the net heat fluxes must be equal to the storage rate of thermal energy: Where is the density of the material, in kg/m3; is the specific heat capacity, in J/(kg⋅°C); and is the partial derivative of the temperature with respect to time. The specific heat capacity is defined by the amount of heat required to cause a change in temperature by 1°C of a unit of mass of the material. Finally, the Fourier's partial differential equation is the simple balance of and , that must be satisfied in every point x for every moment :
3D pore structure, thermal and physical properties of metakaolin-black rice husk ash-based alkali-activated cement
Published in Journal of Sustainable Cement-Based Materials, 2021
Watcharapong Wongkeo, Pincha Torkittikul, Thanongsak Nochaiya, Phakkhananan Pakawanit
The thermal properties of AAC both using NaOH alone and also incorporating it with Na2SiO3 are shown in Figure 10. Thermal conductivity is the ability of materials to conduct heat while heat capacity is the ability of materials to store heat. In this study, analysis of thermal properties was conducted under steady conditions. Thermal conductivity and volume heat capacity of AAC using NaOH alone are shown in Figure 10(a). The results showed that thermal conductivity increased significantly relative to an increasing NaOH concentration, whereas the volume heat capacity seemed to slightly increase. Considering the bulk of samples, the thermal conductivity of the material can be expressed using the thermal conductivities of particular components such as solid form and air void (porosity). The main influence on thermal conductivity is the pore structure such as pore connection and pore size distribution [22]. Large pore structure leads to a decrease in thermal conductivity [23]. Figure 11 shows the relationship between total porosity obtained from XTM and thermal conductivity of AAC. In this study, total pore volume decreased with increasing NaOH concentration resulting in increased thermal conductivity as shown in Figure 11(a). AAC using 10 M NaOH showed the highest thermal conductivity due to the denser microstructure and the decreasing pore volume.
Thermophysical behaviour of LULC surfaces and their effect on the urban thermal environment
Published in Journal of Spatial Science, 2019
Mustafa Naem Hamoodi, Robert Corner, Ashraf Dewan
In order to adjust the LST values of corresponding LULC categories, another theoretical approach was applied based on monitoring the thermal variation of some LULC categories from 9 am to 3 pm at 30 min intervals. This approach was conducted in two steps. In the first step, urban LULC categories were classified into discrete categories with similar thermal behaviour. This was based on the standard heat capacity of each material determined from the literature. Heat capacity is defined as the amount of heat required to increase the temperature of a unit mass of a substance by 1°C (Dupont et al. 2014, Hens 2016, Integrated Environmental Solutions 2011, Jayalakshmy and Philip 2010). The second step adjusted LST measurements by determining the percentage change (increasing and decreasing) in the LST each half-hour for one particular material which was selected from each group. These are listed in Table 3.