Study of the effect of the position and metal of the receiver tube on the performance of a parabolic trough solar collector

In this study, the optical behavior of a parabolic trough collector solar collector has been traced, as the effect of the position and metal of the receiver tube on the optical efficiency and the average local concentration ratio of the heat flux on the receiver tube has been studied. A modeling was performed to simplify the operation of the studied system, where the codes (SOLTRACE and MATLAB) were used. In the first stage, the distribution of heat flux density on the receiver tube's surface was studied using SOLTRACE code based on the Monte-Carlo (Ray Tracing) method. Here the average heat flux on the wall of the receiver tube was obtained after Direct Normal Irradiance was reflected by the reflective mirror. This average will be used as boundary conditions in the MATLAB code, which will allow calculating the optical efficiency of the studied solar collector and the average local concentration ratio on the circumference of the receiver tube. In the second stage of the study, the effect of the metal type of the receiver tube on the optical efficiency and the average local concentration ratio of the heat flow on the receiver tube will be studied, as three metal types were taken for the receiver tubes, the first metal is Copper Black Coated, the second is Aluminum Black Coated and the third is G. Iron Black Coated. The model validation results show good agreement with the literature, with a difference of ±3.29% compared to previous numerical studies. In addition, one of the most important observations that have been reached through this study is that by moving the receiver tube downwards, the concentration area of the heat flux widens but the maximum value of the flux decreases, and the opposite is completely true. The black-coated copper receiver tube gave the best optical efficiency (89.38%) when the focal distance value was 1.88 m, while it was estimated at 75.77% with a focal distance of 1.84 m. The obtained results are very encouraging towards the necessity of carrying out experimental work in this field in order to clarify the physical concept of the behavior of the solar collector studied from the three angles numerically, modeling and experimentally.