집광형 태양열 발전 시스템에서의 태양열유속 분포의 변화에 따른 열전달 수치해석 연구

초록

Concentrating solar power system (CSP) is one of the renewable energies which accumulates solar energy concentrated by condensing mirrors and reflectors in solar absorbers. Boiled water then operates steam turbines to generate electricity. So far, many studies have been conducted for optimization design of CSP which are mostly focused on comparing the materials and dimensions of the absorber to increase thermal efficiency. In this study, we tried to compare heat transfer in solar receiver from different heat flux distributions considering daily change of the azimuthal angle of the solar radiation. A Numerical study was performed using ANSYS FLUENT and appropriate temperature boundary condition was enforced at the receiver inlet using User-Defined- Function. Energy balance was modeled at the receiver inlet considering convectional and radiational loss to the surrounding. The amount of heat transfer to the receiver and heat loss to the surrounding from several characteristic heat flux distributions are compared. In addition, effects from the convective heat transfer coefficient, thermal conductivity, and porosity of the solar absorber are investigated. It has been found that eccentric distribution of the solar heat flux deteriorates thermal efficiency considerably. It is also found that heat transfer becomes larger with small convective heat transfer coefficient and large thermal conductivity. With lowering the porosity, the amount of heat transfer generally increases. But the gain is rather small at very low value with significantly high pressure drop.

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