Mathematical Model of a Sun-Tracked Parabolic Trough Collector and Its Verification

Abstract

The paper presents a one-dimensional distributed parameter model for simulating the transient-state operation of a parabolic trough collector (PTC). The analyzed solar collector has a module design and is equipped with a two-axis sun-tracking system to increase the solar energy yield. The single module is composed of an evacuated tube and a set of parabolic mirrors acting as reflectors. In each of the collector tubes, two aluminum U-tubes are installed, enabling heat intake by the solar fluid. The collector is intended for household applications, as well as other medium thermal energy demand uses. During the numerical model development, appropriate energy balance differential equations are formulated for the collector individual components. The equations are solved using different schemes. As a result, a time- and space-dependent temperature series for each of the collector components and the working fluid are obtained. To select an appropriate time and spatial steps for the developed model and to verify the reliability of the results received, the collector model is also implemented in ANSYS Fluent. The results of the one-dimensional model calculations and comparisons carried out in ANSYS demonstrate considerable agreement. In particular, the values of the fluid temperature at the collector outlet, calculated using the model developed, show high consistency with the ANSYS Fluent results. Furthermore, a preliminary experimental verification of the proposed model is carried out on a test stand currently under construction. The computed and measured temperature course of the fluid at the collector outlet is compared. In this case, the results are also satisfactory.