A comprehensive review on the application of nanofluids and PCMs in solar thermal collectors: Energy, exergy, economic, and environmental analyses

Background: Solar energy is broadly utilized in various applications, including solar thermal collectors (STCs), heating, desalination, etc. The SCs are employed to convert solar energy into thermal one. Utilizing nanofluids (NFs) and phase change materials (PCMs) can improve the performance of STCs by enhancing the rate of heat transfer. Methods: The present review paper describes NFs and PCMs, explains STCs, and provides different advances in these subjects. The influences of NFs and PCMs on the performance of STCs are examined. In addition, energy, exergy, economic, and environmental considerations are evaluated, and finally, current challenges and future directions are discussed. Significant findings: It was observed that the use of NF and PCM leads to a significant improvement of the energy and exergy functions of STCs. Also, Also, it was found that a limited number of studies have been done on the performance of NF-based STCs from an economic and environmental point of views, and all of them have reported the positive effect of NFs on the performance of these systems. Moreover, it was revealed that the employment of NFs in the STCs depends on their long-term stability and preparation costs. Therefore, more laboratory investigations are required to characterize thermophysical properties of NFs

The mechanical properties and corrosion behavior of quaternary Mg-6Zn-0.8Mn-xCa alloys

In present study, the influence of calcium content on the microstructure, mechanical properties and corrosion behavior of quaternary Mg-6Zn-0.8Mn-xCa alloys, where x = 1, 1.5, 3 or 4.5 wt.% Ca, was examined. The grain structure of this quaternary alloy system became more refined with increasing additions of Ca. In addition to a-Mg, the Ca2Mg6Zn3 phase was found to be present in Mg-6Zn-0.8Mn-1Ca and Mg-6Zn-0.8Mn-1.5Ca according to microstructural and thermal analysis (TA). In addition to the a-Mg and Ca2Mg6Zn3 phases, the Mg2Ca phase was found to be present in the Mg-6Zn-0.8Mn-3Ca and Mg-6Zn-0.8Mn-4.5Ca alloys. Alloys with 1 or 1.5 wt.% Ca led to increases in the tensile strength of Mg-6Zn-0.8Mn, although further Ca additions had a deleterious effect. The TA of Mg-6Zn-0.8Mn-xCa during its solidification indicates that the fraction of liquid phase increases with increasing Ca content at the dendrite coherency point, leading to an increase in secondary phases and increased corrosion rate of Mg-6Zn-0.8Mn-xCa alloys