C.A. Pérez-Rábago

High-heat-flux sensor calibration using calorimetry

This paper demonstrates a calorimetric procedure for calibrating high-heat-flux sensors. The results are in agreement with calibrations obtained using black-body radiation. However, the proposed method has the potential of being more accurate than traditional approaches. This new procedure calibrates sensors to measure correctly under conditions of concentrated solar radiation. At present, the thermal balance calibration technique in the laboratory is limited to solar irradiances of approximately 100 kW m−2. The next step is to demonstrate this methodology to higher irradiances under non-laboratory conditions in the CIEMAT solar furnace at Plataforma Solar de Almeria.

Assessment of a polymeric reflective coating for high concentration point focus applications

A methodology for the evaluation of the specularity error of a polymeric film optical coating is presented. The methodology is based on the comparison of images from the sun produced by two high quality spherical mirrors, one covered with a highly specular evaporated aluminum film, and the second one with the polymeric film under study. This film is a commercial product known as Reflectech®. To determine the specularity error, both images are reproduced by means of ray tracing optical simulations. Those simulations use the angular brightness distribution from the sun as input, which were recorded by means of a specially developed solar scope. Significant differences are obtained between images of the sun generated by both mirrors. However, the specularity error of the coating under consideration is found to be just 0.71 mrad. This error is quite small making the polymeric coating highly appropriate for point focus concentration systems. This is illustrated by calculations for a parabolic dish concentrator.

Numerical approach to the flux distribution effect on a solar rotary kiln performance

New investigations on solar thermochemical storage and other high temperature process are starting at the University of Antofagasta. A small cavity-type solar rotary reactor will be constructed to develop gas-solid reactions. For this reactor concept, is expected that the most part of the solid reactants will remain in the central sector of the drum. Thus, high temperatures at this area will benefit the process performance. Since the radiation profile feeding the solar reactor could have a significant effect on the temperature distribution, in this work it is presented a numerical model to analyze how the use of different concentrators affects the cavity walls temperature. First, a reference case was simulated with flat profile radiation. Then, a solar simulator composed of an elliptical mirror and a high power lamp and a multi-faceted concentrator were considered for the analysis. Their radiation profiles were obtained by ray tracing simulations and integrated in a CFD model that predicts the cavity temp...

Experiments with Cavical in the Solar Furnace of the PSA

This paper presents the experimental results on the thermal characterization of a special conical cavity calorimeter named CAVICAL. The experiments were done on the Solar Furnace (SF) at Almeria Solar Platform in Spain (PSA). The CAVICAL was previously used to measure the thermal power of a point focus solar concentration system named DEFRAC and developed at the Center of Energy Research of the National University of Mexico. The detailed theoretical heat transfer study on that instrument was done using the FLUENT code. The heat transfer mechanisms that were taken into account in the theoretical analysis were the radiative energy absorbed by the inner wall cavity, the energy transfer from the wall cavity to the air by natural convection, the energy transferred by conduction through the metallic wall of the calorimeter and by forced convection through the fluid in the cooling system. The calorimetric information allowed determining the thermal power that the concentrator is able to capture. Now, the purposes of the experiments, which results are presented in this paper, were to validate the theoretical model and to determine the relationship between the wall’s temperature distribution in the calorimeter cavity and the radiative incident flux on the conical calorimeter.