Thermal performance model and parametric studies of a trapezoidal Fresnel solar receiver

Abstract:

Amongst the current technologies to profit the solar resource by concentration, Linear Fresnel Collector (LFC) is the most relevant to achieve significant improvements. In general, for solar concentrated technologies, the receiver is a key element to be improved. Moreover, in not industrialized countries, such as Ecuador, the development of these technologies should be made with the local capacities to avoid external dependence. In this work a simplified thermal model has been developed using the thermal resistance concept. This model is capable to pbkp_redict the thermal behavior of a trapezoidal LFC receiver. The model was validated by comparison with a similar model in a CFD program. The model was used to study the thermal performance of a 100 m LFC receiver. The temperatures and heat transfer rates on all surfaces and air cavity were computed. Results showed that the radiation heat transfer is predominant in such a receiver. Moreover, with the increase of temperature the increase of radiation is important, while convection remains almost constant. Efficiencies close to 89% were reached under the imposed conditions. Additionally, some parametric studies were carried out to understand the influence of using selective coating on the absorber and of varying the mass flow rate. Differences of more than 3% were found when a selective coating is used over the absorber. This difference increases as the temperature increases. It permits to conclude the importance of using selective coating in this kind of receivers. Regarding the influence of the mass flow rate, the energy efficiency increases as the mass flow rate increases. However, since the outlet HTF temperature decreases in the same proportion, it is necessary more receiver length to achieve the same outlet HTF conditions. Results suggest that a 2 kg/s mass flow rate is the better option for the imposed conditions.

Año de publicación:

2018

Keywords:

Fuente:

scopus