Exploring the photo-thermal conversion behavior and extinction coefficient of activated carbon nanofluids for direct absorption solar collector applications

Thermal performance analysis of a flat-plate solar heater with zigzag-shaped pipe using fly ash-Cu hybrid nanofluid: CFD approach

Regarding the detrimental impacts of using non-renewable energy resources on the environment and the importance of increasing heat transfer in heat exchangers, this research is aimed to increase the heat transfer surface of the collector pipe in contact with the absorber plate at the flat-plate solar collector by designing the pipe in a zigzag shape instead of conventional straight pipe. The 3D coupled investigation of fly ash-Cu/water hybrid nanofluids and analyzing the thermal performance of the proposed solar collector comprising zigzag pipe are the innovation of this research. Also, the effect of variations in mass flow rate, fluid inlet temperature, the volume fraction of nanoparticles on thermal efficiency, Nusselt number, pressure drop, Rayleigh number, and rate of heat transfer coefficient in three irradiations with two types of working fluids have been investigated. Results indicate that due to the enhancement in heat transfer surface in the case where the fluid path is zigzag, the thermal efficiency has improved compared to the straight pipe. In addition, with enhancing mass flow rate, temperature, and irradiation, the average Nusselt number increased. The heat transfer coefficient and pressure drop have the highest value by utilizing 0.5% and 3.5% nanoparticle concentration up to 10.84% and 7.603%, respectively, at a mass flow rate of 0.0089 kg/s, and irradiation of 800 W/m2. Finally, by calculating the efficiency index of the proposed flat-plate solar collector, the proper volume concentration for using copper-fly ash/water hybrid nanofluid is obtained at fraction of 0.5% and a mass flow rate of 0.0045 kg/s.

A MATLAB simulation-based analytical study of energy, exergy, and cost benefits in jet-impinged protrusion-roughened double pass solar air collector

This study analyzes the performance and cost-effectiveness of a protrusion-roughened jet-impinged double-pass solar air collector (PRJDPSAC) within a Reynolds number (Re) range of 2500 to 22,500. Examining jet slot parameters, i.e., the jet height ratio (Hjp/Dhd = 0.11-0.44), stream-wise pitch ratio (Xjp/Dhd = 0.44-1.32), and span-wise pitch ratio (Yjp/Dhd = 0.44-1.32), the model demonstrates enhanced energy conversion, minimizes losses, improves efficiency, and brings positive economic impact, making it a promising solution for diverse applications including drying processes, livestock facilities, remote accommodations, and HVAC system pre-heating. The examination incorporates advanced MATLAB simulations to assess energy-exergy performance and cost viability. At lower Re values, both energy ([Formula: see text]) and exergy ([Formula: see text]) efficiencies increase uniformly; however, stabilization and decline occur at higher Re values. The maximum [Formula: see text] for the PRJDPSAC is 4.38% under a temperature rise parameter of 60 × 10-3 Km2/W for obtaining optimum values of Xjp/Dhd = 1.32, Hjp/Dhd = 0.22, and Yjp/Dhd = 1.32, which is 31% higher than that of the smooth double-pass solar air collector (DPSAC). Economic benefits are significant for PRJDPSAC within mair (0.01-0.07 kg/s), but above 0.07 kg/s, the DPSAC becomes more cost-effective. Integrating simulation and experimental data, the study highlights MATLAB's effectiveness for solar energy system analysis and optimization, reinforcing the practicality of the proposed collector design.

Challenges, limitations, and applications of nanofluids in solar thermal collectors-a comprehensive review

The daily increase in the demand for energy consumption is partly caused by the global population explosion and advancements in technology. Humanity relies on energy to fulfil its daily routines, such as electricity for lighting, heating, cooling, and running electronic devices. There are continuous attempts by researchers and industry experts to optimize and enhance the efficiency of various sustainable energy generation devices. Solar collectors play a critical role in the renewable energy sector, which is vital in helping the world achieve a clean, green, and sustainable environment. Over the last two decades, researchers have made significant efforts to explore various techniques for enhancing the effectiveness of solar thermal collectors. Their effort has been centered around improving the fluid thermal properties, which act as the heat transfer medium in solar collectors. The discovery of nanofluids will help resolve some of the challenges associated with conventional fluid used in solar collectors. Enhancement through nanofluids is influenced by several factors, which include nanoparticle types, nanoparticle concentration, base fluid, and the purpose of its application. This review provides a technical summary of the application of nanofluids in the two main types of collectors: non-concentrating and concentrated thermal collectors. Findings from this study showed that TiO2 + Cu hybrid nanofluids with a mass fraction of 0.03 augment heat transfer coefficient by 21% in parabolic trough collectors. The merits of employing nanofluids as heat transfer fluids in solar collectors are examined, while also outlining the obstacles and areas where further research is needed.