A NEW MODEL FOR THE ANALYSIS OF PERFORMANCE IN EVACUATED TUBE SOLAR COLLECTORS

摘要

This paper describes a new model for the performance analysis of evacuated tube solar collectors. The analyzed collector is equipped with truncated compound parabolic reflectors, but the analysis is also extended to the case of collectors without reflectors. An original software is developed under MATLAB environment for the simulation purpose. A novel numerical procedure is implemented to obtain the solution for the nonlinear set of equations representing the mathematical model. In the model, the variation of important parameters is considered in the circumferential, longitudinal and radial directions. The length of the tube, where the heat transfer fluid flows, can be divided into a specified number of segments and the energy analysis is performed for each segment along the tube length in order to obtain the variation of different parameters in the longitudinal direction. The model analyzes separately the optics and the heat transfer in the evacuated tubes and this approach allows to extend the analysis to new configurations. The model can simulate the efficiency curve under steady-state conditions, according to the standard EN 12975-2 (EN 12975-2. Thermal solar systems and components - solar collectors - part 2: test methods. Brussels: CEN; 2006). A comparison with experimental data shows the accuracy of the present model.