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Research dedicated to renewable energies aims at reducing the negative impact of fossil fuels on the ecosystem and particularly to solar applications so to make it more competitive with conventional systems. In this paper, attention is paid to flat plate solar air collector due to their simplicity and immediate use in converting solar energy, and operating at low temperature. A modification has been brought to one of its components to further improve its performance. To meet the needs of thermal energy demand for a given use (heating, drying, etc.), an installation of a field of collectors (solar air collector, solar water heater, etc.) is required to ensure the demanded thermal power. The modification consists in integrating, on the back of the solar air collector, a water tank supplied by solar water collectors, which serves as a heat storage tank for any other use. A simulation is performed using Fluent CFD code, in order to follow the evolution of the heat transfer fluid flow considering the implantation site meteorological data at Bouzaréah (Algeria). Different flow rates were considered for the two heat transfer fluids. A primary heat transfer fluid was represented by air and the second one represented by water. Simulation results show that thermal efficiency of the modified solar air collector is improved compared to the one of the typical solar air heater when we use forced flow. For the different used flow rates, higher efficiency is obtained when the flow rate of the primary heat transfer fluid (air) is increased.

The investment of solar energy in life applications has become mandatory to maintain a clean environment and reduce the use of fossil fuels. This work aimed to improve the performance of solar air heater (SAH) by using evacuated tube solar collectors ETSC integrated with nano-enhancer phase change material (NE-PCM). To achieve this purpose, a system consisting of 5 linked collecting panels was designed, fabricated, and experimentally investigated. Each panel included a glass-evacuated tube with two concentric aluminum pipes installed inside. NE-PCM was placed between the inlet and outlet air paths inside the evacuated tube to enhance the heat transfer rate. The performance was investigated with and without NE-PCM at five mass flow rates (0.006, 0.008, 0.01, 0.03, and 0.05 kg/s). Experimental results revealed that the highest temperature was 116, 108, 102, 95, and 93 °C, respectively, for the above mass flow rates without adding NE-PCM. The outlet temperature was decreased by 6–15 °C when using NE-PCM. The SAH efficiency was increased by 29.62% compared to the system without NE-PCM at 0.05 kg/s. The maximum thermal efficiency for the system with NE-PCM was 62.66% at 0.05 kg/s, and the pressure drop was 6.79 kPa under the same conditions. As well known, the hot air is used for a variety of purposes including space heating, food processing, drying of fruit, vegetables, dairy, and solar cooking.

Solar water heaters are a type of renewable energy technology that converts solar energy into heat to warm water. Solar water heaters are becoming increasingly popular due to their eco-friendliness, cost-effectiveness, and low maintenance requirements. In this study, low-cost solar collectors were developed using date palm waste (dried leaves) as thermal insulation. Date palm waste is a readily available and abundant resource in many regions, and using it in solar collectors can help reduce waste and promote sustainability. Two solar collectors were fabricated using crushed date palm waste, with one collector using the waste alone and the other mixed with starch. Tests were conducted in accordance with the European standard EN 12975–2-2006 and modeled the thermal behavior of the collectors. The results obtained showed that the prototypes of solar collectors performed well and exhibited behavior comparable to that of a commercial solar collector, with a production cost up to three times less. The use of date palm waste as thermal insulation in solar collectors is an innovative approach that aligns with the principles of sustainability and environmental friendliness. Furthermore, it was found that the leveled heating cost ( LCOH ) and the simple payback period ( SPP ) were 0.952 US$ kWh −1 and 2.472 years for the prototype without starch and 0.926 US$ kWh −1 and 2.397 years for the prototype with starch.

The objective of this research article is to present a comprehensive review of the work carried out to improve the thermal as well exergetic performance of the conventional smooth absorber plate solar air heater (SAH) duct by the use of the various configurations and arrangements of extended surfaces (fins) for the forced convection. In the SAH duct, these extended surfaces are attached along the air-flow path on the top absorber, on the bottom plate, or on the both plate surfaces. It enhances the performance of the conventional SAH by increasing the surface area and makes flow turbulent by their presence. Several experimental, theoretical, and simulation works, which have been performed by the researchers by utilizing the extended surfaces to improve the thermal efficiency based on first law of thermodynamics, exergy, and entropy generation analysis on the basis of the second law of thermodynamics for SAH ducts, have been included in the present article. Subsequently, an effort has been made to calculate the Nusselt number and friction factor by using the correlations reported by the researchers for comparing the performance of different configurations of fin SAHs. This comprehensive review article will be useful for the investigators and researchers who are working in the area of extended surface SAHs.

The thermal efficiency of conventional solar air heater is very low. This research article concentrates on incorporating V-shaped staggered twisted ribs over absorber surface of solar air heater. Various roughness parameters were tested to determine their effect on the Nusselt number, friction factor, thermo-hydraulic performance index, and thermal efficiency. During experiment, the Reynolds number is varied from 3000 to 21,000; while relative roughness length varied for 4.39 to 10.26 and relative staggered distance for 2 to 6. However, relative roughness pitch, twist length, and angle of attack were kept constant. The Nusselt number and friction factor of the roughened collector enhances to 3.41 and 2.56 times that of the smooth collector, respectively. The thermal efficiency of the roughened solar air heater increases to 73.64% of the roughened plate as it was noticed 42.63% for smooth surface due to breakage of the laminar sublayer. The correlations for Nusselt number and friction factor as function of Reynolds number and roughness parameters are also developed. The maximum thermohydraulic performance gained at the optimum parameters of d / e of 4 and S / e of 6.15 is 2.69. The percentage deviation between the developed correlations and the experimental findings shows very satisfactory outcomes. Therefore, it can be concluded that inclusion of twisted V staggered ribs enhances the thermal performance of solar air heater with the lowest frictional penalty.

To investigate the solar air heater’s (SAH) effectiveness, experiments are conducted using flat plate and artificially roughened plate in terms of inclined and winglet baffles over the collector surface. This proposed system collector plate is made up of inclined and winglet ribs and serves as an artificial roughness generator. Air stream of 0.01, 0.02, and 0.03 kg/s are used in the experiment. To determine the improvement in the proposed work, these experimental results are compared with flat plate SAH. This proposed work offers a greater efficiency, useful energy gain, and lower top heat loss than a conventional SAH. At 0.03 kg/s system efficiency and useful energy gain reach their peak. Experimental day’s average efficiency of a SAH with inclined and winglet baffles is 30.8%, 52.7%, and 72.9%, respectively, for the examined cases, and it is 11%, 13.8%, and 22.2% more effective than a flat surface SAH. For the investigated air flow rates, the proposed system gains 36.2%, 24.2%, and 28.9% more energy than flat plate SAH. Substantial reductions in top losses of up to 8.48%, 7.28%, and 7.27% have been reported at the specified flow rates, respectively. Energy metrics and economic study performed show the payback time, production factor, life cycle conversion efficiency, and economic values of the proposed SAH are optimum.

A solar collector is a simple and cheap device that converts solar radiation into valuable heat energy. The thermal performance of the solar collectors can be enhanced significantly with the suspension of nanoparticles in the base fluid. A novel design for a solar-assisted water heater (SWH) is proposed in the current study, and the effect of nanofluid has been investigated on the thermal efficiency of the SWH. The use of nanofluid is one of the prominent methods in comparison to other techniques for improving the performance of solar collectors. Therefore, the base working fluid, i.e., water is mixed with the alumina nanoparticles of average particle size of 30 nm, and they are assumed to be spherical. The flow and thermal characteristics of nanofluid through the solar water heater are simulated numerically with the help of the Eulerian–Eulerian two-phase model using the finite volume method (FVM). The commercial package ANSYS Fluent, is used for modeling the problem under transient conditions with a pressure-based solver. In comparison to a conventional flat plate collector, the proposed solar water heater consists of a corrugated absorber-plate and the effect of the radius of curvature has been investigated on the heat transfer and collector efficiency. With the proposed design, the heat transfer area available with the riser tubes increases remarkably and it leads to a 43% and 14% increase in heat transfer augmentation and collector efficiency, in comparison to the conventional solar water heater.

Solar air heaters (SAH) convert solar energy to thermal energy for food processing industries and commercial space heating applications, as solar energy is cost-free. In this experimental study, the thermal performance of the solar air heater has been successively improved using different roughness elements over the absorber. The triangle-shaped wedges in three structures (inline, serpentine, and clustered structure) are investigated in this work. Thermal performance comparison is made with a SAH with a plain absorber. A maximum air temperature rise of 19 °C is observed for the SAH with wedges in a clustered structure. The absorber surface temperature for clustered structured roughness elements is 76.8 °C with an average heat loss coefficient of 4.43 W/m 2 ·K. The useful heat absorption using clustered structure wedges is 33%, 17.9%, and 6.6% higher than the SAH with plain, inline, and serpentine structured wedges. SAH’s maximum thermal and exergy efficiency with clustered structured elements is 70.4% and 1.64%. The average thermal efficiency of inline, serpentine, and clustered arrangement is 13.3%, 25.3%, and 35.6% higher than the SAH with a plain absorber. The proposed SAH design shows a sustainability index 1.01, and lower payback periods show economic and environmental viability.

Solar air heater is widely used for drying and industrial processing application. Different artificial roughened surfaces and coatings over the absorber plates are used to improve their performance of solar air heater by increasing absorption and heat transfer. In this proposed work, the graphene-based nanopaint is prepared by wet chemical and ball milling method and the prepared graphene nanopaint is characterized using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The prepared graphene-based nanopaint is coated on the absorber plate by conventional coating method. The thermal performance of the solar air heater coated with traditional black paint and graphene nanopaint is evaluated and compared. The day’s maximum energy gain by the graphene-coated solar air heater is 972.84 W, whereas traditional black paint is only 808.02 W. The average energy gain of graphene nanopaint is 655.85 W, which is 12.9% higher than the traditional black paint. The maximum thermal efficiency for solar air heater coated with graphene nanopaint is 81%. Also the average thermal efficiency of graphene-coated solar air heater is 72.5%, which has a 13.24% higher average thermal efficiency when compared to conventional black paint-coated solar air heater. The average top heat loss for solar air heater coated with graphene nanopaint is 8.48% lower than solar air heater with traditional black paint.

The current article unleashes an experimental research in context to a solar air heater in which jet impingement technique has been simultaneously used with array of fins. An earnest attempt has been made to depict the significance of important geometrical parameters, namely fin spacing ratio, jet diameter ratio, and stream-wise pitch ratio, on the heat transfer of this new duct. The experiments were conducted for a range of mass flow rate, m˙ = 0.056–0.112 kg/s, and Reynolds number (Re) = 5700–11,700. It is observed that heat transfer rate is certainly enhanced by this excellent idea which substantiates the novelty of this research. The experimental results are validated with reference to the smooth (conventional type) solar air heater. The distribution of enhancement factor with Reynolds number as a function of above-mentioned geometrical parameters has been presented. A substantial enhancement in heat transfer of the order 2.5 times has been reported in comparison with the simple flat-plate (conventional type) duct at the higher values of Reynolds number. The experimental data collected are accessed to derive a correlation for the Nusselt number as a function of relevant geometrical and operational parameters of the duct.