Introducing two scenarios to enhance the vacuum U-tube solar collector efficiency by considering economic criterion

Background: Solar domestic hot water systems heat water by receiving sun's radiant energy using solar thermal collectors. Solar collectors absorb the sun's rays and convert them to heat. This heat is then absorbed by the working fluid, which passes through the collector and may be stored or used directly. Since solar collectors are the most important part of solar water heating systems, this study offers some techniques to improve their efficiency. Method: In this experimental study, the thermal efficiency of a vacuum tube solar collector was improved using three types of absorber tubes. Nanofluid of silica/water-ethylene glycol was incorporated inside the absorber tubes. Experimental data including instantaneous inlet and outlet temperatures, ambient temperature and solar radiation were measured. Comparisons were performed between the thermal performance of spiral-tube as well as helical-coil and U-tube. Findings: Experimental results revealed that the use of both spiral and helical-coil tubes improved the efficiency significantly, in which the helical-coil tubes performed much better. In addition, in the absence of nano-additives, economic calculations revealed that using spiral and helical-coil tubes increased the cost by 60% and 72%. In the case of nanofluid, the use of nanofluids in the helical coil intensified the cost by 3.4 times. (c) 2021 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Automated summary

This experimental study focuses on improving the thermal efficiency of vacuum tube solar collectors by using different types of absorber tubes and incorporating nanofluid technology. The results showed that spiral and helical-coil tubes significantly enhanced efficiency, with helical-coil tubes performing better. However, the cost increased when using nanofluids in the helical coil.