Akademik Veri Yönetim Sistemi
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, cilt.239, ss.1-20, 2025 (SCI-Expanded)
In this study, a systematic, detailed thermodynamic analysis model that considers all forms of heat transfer, entropy and exergy in a direct absorption solar collector (DASC) is proposed. In this model, heat conduction, heat convection and collimated irradiation are considered, and the entropy generation rate (EGR) due to collimated radiation and the exergy balance equation are derived. Based on numerical calculations representing a large number of cases, the correlation equation between the spectral properties and the exergy efficiency of a DASC is established. Materials with different spectral distributions can be evaluated directly, without the need for a numerical solution to the radiative transfer equation (RTE), using the relationship defined here. The numerical results show that at low values of the optical thickness (τ = 0.1 and τ = 1.0), the radiative heat transfer in the medium dominates the heat transfer phenomena, whereas at high values of the optical thickness (τ = 10.0 and τ = 100.0), the absorption and scattering in the medium predominate. The EGR due to scattering reaches close to 40 %, and is significantly higher compared to systems without collimated irradiation. The scattering property of the participating medium should be taken into account when analysing DASCs. The concentration of nanoparticles has an important effect on the exergy efficiency of DASC, which increases by 380.5 % when the concentration increased from 0.2 ppm to 1.0 ppm. Based on the numerical results, the impact coefficients of the spectral properties of the absorbing boundary, reflecting boundary and the participating medium in the correlation equation are found to be 2.6699, 0.0012 and −1.1678, respectively, and the radiative property of the absorbing boundary is shown to have the most significant effect.