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SUMMARY The numerical simulation and experimental validation of a compound parabolic concentrator (CPC) are presented. The solar device had an aperture area of 1.33 m2, a real concentration ratio of 3.5, an acceptance half angle of 15°, and a carbon steel (or aluminum) tubular receiver with an outer diameter of 0.0603 m and coated with a commercial selective surface. Experimental tests were performed using water as working fluid at solar noon; the inlet temperatures used varied from 30 °C to 70 °C and the mass flow rates from 0.05 kg/s to 0.25 kg/s. A comparison of the experimental results with the numerical model developed was carried out. The results of the thermal efficiency, outlet temperature, and pressure drop were compared and found to be in close agreement with the experimental data. Therefore, the model is a reliable tool for the design and optimization of compound parabolic concentrators. Because the numerical model is based on the application of physical laws, it is possible to extrapolate its use with confidence to other fluids, mixtures, and operating conditions. Copyright © 2011 John Wiley & Sons, Ltd.

A solar concentrator was designed using a detailed one-dimensional numerical model previously developed to describe the heat and fluid-dynamic behavior inside a compound parabolic concentrator (CPC). The governing equations (continuity, momentum and energy) inside the CPC absorber tube, together with the energy equation in the tube wall and the thermal analysis in the solar concentrator were solved. Two CPC geometries were proposed based on numerical simulation and commercial availability of materials; one of this is tested in this work. A ray tracing analysis was made for this configuration to quantify optical energy losses due to truncation. Then, a module with aperture area of 2.1 m 2 was constructed. The module has 12 CPCs, each one with real concentration ratio of 1.8, acceptance angle of 30°, and a tubular receiver covered by a selective surface. An experimental setup was designed and built to test different operational conditions for the module; for example mass flow rate and inlet temperature. The experimental setup has the following elements: The CPC, two water storage tanks, a recirculation pump, and a support structure that allows positioning the CPC at different angles. Experimental results obtained using the Mexican standard NMX-ES-001- NORMEX-2005 show that this technology could be able to supply stable temperatures for industrial processes. However, a new prototype is going to be developed and constructed in order to improve some manufacturing errors detected in these experimental tests. NomenclatureA Cross section area [m 2 ] e Specific energy (h+v 2 /2+gz sin ) [J/kg] g Acceleration due to gravity force [m/s 2 ] h Enthalpy [J/kg] I Solar irradiance [W/m 2 ] m Mass [kg] . m Mass flow rate [kg/s] p Perimeter [m] P Pressure [Pa] I. Santos-González et al. / Energy Procedia 57 ( 2014 ) 2956 -2965 2957 . q Heat flow per unit area [W/m 2 ] Q Heat energy [W] t Time [s] T Temperature [°C] v Velocity [m . s -1 ] x g Vapour quality [dimensionless] Greek letters P Pressure drop [Pa] T Temperature difference [°C] z Axial discretization step [m] Efficiency [dimensionless] Inclination angle of absorber tube [degree] Density [kg/m 3 ] w