THEORETICAL EXPERIMENTAL METHODOLOGY FOR EVALUATION OF PERFORMANCE OPTICAL COLLECTORS CONCENTRATORS PARABOLIC CYLINDER TYPE
DOI:
https://doi.org/10.59627/cbens.2012.2239Keywords:
Linear collectors, Optical efficiencyAbstract
This paper presents a simple methodology that allows evaluating indirectly the optical performance, and other variables, of parabolic cylinder collectors. The methodology calculates the optical performance considering the set of properties and parameters that affect the same, not requiring knowledge of their individual values (e.g., reflectivity and absortivity of the mirror surface; transmissivity of the tube receptor; and the intercept factor) that are difficult to measure experimentally. The material properties reported by the manufacturers do not represent reality, because during the life time of the collector there is possibility of degradation of these materials due to their exposure to the weather. Also the reflective surfaces are susceptible to deformation and bulging due to problems of expansion and action of climatic factors such as heavy rain and hail, wind drag with abrasive material, etc. The methodology, based on material available in (Duffie & Beckman, 2006), developed an algorithm that was implemented on the platform EES (Engineering Equation Solver). The input variables are the inlet and outlet temperatures of the working fluid, the volume flow rate of the fluid, the direct solar radiation, the ambient air temperature and the wind speed. The required parameters are dimensional data of the collector (e.g, concentration ratio, tube diameters and length). Among the output variables the most important are the optical efficiency, the absorbed radiation, and the thermal of the collector. For this work we used experimental data from tests performed in the facility's solar concentrators CEFET-MG. The results indicate a maximum optical efficiency of 50%. The model also shows the dependency of the optical performance with the angle of incidence of radiation.
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