Heat losses from the absorber of a parabolic trough medium-enthalpy collector

Abstract

 The global heat loss coefficient of solar thermal systems is a critical parameter for assessing the efficiency of these systems. This coefficient represents the heat losses from the system to the environment through mechanisms such as conduction, convection, and ra­diation. Its determination is essential for performing energy balances and characterizing different solar technologies. For concentrating solar systems, both experimental and numerical methods are performed for its calculation. This work presents a custom-designed parabolic trough absorber as a case study, being the infrared thermography technique is employed to quantify the global heat loss coefficient. It was determined that the absorber has a thermal global loss coefficient of 50 W/m²°C, considering only the sections with glass covering. The predominant loss mechanism is convective, reaching up to 700 W of total thermal losses, while radiative losses reach 350 W of thermal losses. The results of this study would make possible the optimization of the absorber design and the improvement of the solar thermal system efficiency.