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In this work, the effect of applying nano-enhanced absorber coating on the energetic and exergetic performance of an unglazed vertical solar air heating system has been analyzed numerically and experimentally. In the first step of the research, various configurations of vertical solar air heaters including hollow, baffled and perforated baffled systems have been surveyed by using computational fluid dynamics. According to the numerically obtained findings, the system with perforated baffles gave the best performance metrics. In this regard, two heating systems with perforated baffles have been manufactured. One of the system was painted with a regular matt black paint while CuO nano-embedded black paint applied to the other solar heater. Fabricated heaters have been experimentally surveyed at three different flow rates. Thermal efficiency values for the heaters with and without nanoparticles were found between 58.10-76.22% and 54.96–72.05%, respectively. Applying nano-embedded coating increased the exergy efficiency in the range of 9.25–10.58%. In addition, maximum deviation of numerically and experimentally attained outlet temperature values was calculated as 4.74%. Moreover, general findings of this research showed the successful utilization of nano-enhanced absorber coating. [ABSTRACT FROM AUTHOR]

Photovoltaic-thermal (PVT) collectors can be applied in order to concurrently generation of electrical and thermal energy. In the present study, a vertical hybrid PVT solar dryer has been developed and analyzed by utilizing numerical and experimental approaches. ANSYS Fluent software has been employed to visualize both flow and thermal behavior inside the vertical PVTs. The main aim of using vertical structure of PVT dryer is its space-saving potential. For enhancing heat transfer, fins have been integrated over the absorber plate and PV panel. The obtained experimental findings showed that thermal efficiency values of the finless and finned vertical PVT collectors were in the ranges of 47.46–54.86% and 50.25–58.16%, respectively. Moreover, sustainability index values of finless and finned drying systems were achieved between 2.16-2.75 and 2.38–3.25, respectively. The obtained results showed that applying high air flow rate in finned vertical dryer notably improved the drying performance. In addition, the deviation between numerical and experimental findings obtained in the range of 4.2–8.7%. [ABSTRACT FROM AUTHOR]

Solar air heaters (SAHs) are generally used in different applications because of their simple structure, low setup cost, and also their higher energy conversion efficiency. In this study, a v-groove type SAH (VTPSAH) has been developed, manufactured and compared with parallel-pass SAH (PPSAH) and double-pass SAH (DPSAH) under same climatic conditions. In addition to the experimental analysis, CFD simulation of SAHs has been done to investigate heat and flow behavior inside the systems. The experiments have been performed in 0.015 kg/s, 0.013 kg/s and 0.011 kg/s mass flow rates on February and June to evaluate the performance of SAHs at various climatic conditions. According to the obtained results, annual average thermal efficiency for PPSAH, DPSAH and VTPSAH were obtained as 54–60.29%, 61.86–66.95% and 70.91–78.18%. The maximum instantaneous thermal efficiency was achieved in all tests as 90.65% in highest mass flow rate in VTPSAH in February. Exergy efficiency values for VTPSAH, DPSAH and PPSAH were obtained in the range of 14.62–18.95%, 12.28–15.68% and 6.68–9.74%, respectively. Moreover, Enviro-economic costs were found between 4.22 and 7.66 $/year. Also, the highest deviation between numerical and experimental results is 10%. • Comparative performance analysis of parallel-pass, double-pass and v-groove triple-pass solar air heaters. • Maximum 10% deviation between numerical and experimental results. • Maximum instantaneous thermal efficiency has reached 90.65%. • Exergy efficiency values were obtained in the range of 6.68–18.95%. [ABSTRACT FROM AUTHOR]

Solar thermal systems like solar water and solar air collectors (SCs) are generally used because of their simple structure and high thermal efficiency. Solar air collectors could be utilized in drying applications because they are easy applicable and economical. In this study, a novel parallel-pass SC with double baffles (PPSCDB), parallel-pass SC with baffles (PPSCB) and parallel-pass SC (PPSC) without baffle have been designed and tested for drying application. Baffles have been manufactured in plus-shaped and perforated to achieve high thermal performance. The performance of solar collectors has been analyzed numerically and experimentally. In addition, a drying chamber has been coupled with solar air collectors. Celery (Apium Graveolens L.) root has been dried as a product and dried samples' quality has been analyzed experimentally. The experiments have been conducted at 0.009 kg/s and 0.011 kg/s air mass flow rates. According to the experimental findings, average thermal efficiencies of PPSC, PPSCB and PPSCDB are in the range of 62.10–66.32%, 65.72–69.62% and 71.12–75.11%, respectively. The highest instantaneous efficiency was obtained as 84.30% in higher mass flow rate in PPSCDB. Also, maximum deviation between experimental and numerical results was 9.5%. • Effect of integrating plus-shaped perforated baffles to solar air collector. • Comparing of different configuration of baffles in solar dryers. • The highest instantaneous efficiency was obtained as 84.30% with single air channel. • Validation of numerical simulation by experimental analysis. • Antioxidant, color, phenolic and flavonoid content analysis of celery root. [ABSTRACT FROM AUTHOR]

In this study, the impact of combined usage of infrared heater and nano-improved absorber coating in the triple-flow solar dryer (TFSD) has been analyzed. In the first stage of the study, a newly developed baffle configuration in the triple-flow solar air collector (SAC) has been numerically analyzed utilizing computational fluid dynamics. The new configuration was compared numerically with the conventional collector. Considering the numerical results, a triple-flow SAC with perforated baffles was manufactured and coupled with a drying room. In the experimental part, a conventional TFSD, an infrared-assisted TFSD and an infrared-assisted TFSD with iron (Fe) nano-embedded absorber coating (industrial matt black paint) have been examined. According to the experimentally obtained findings, combined usage of infrared heater and nano-improved paint decreased the drying period by 40% compared to the conventional TFSD. Thermal and exergetic efficiencies of the triple-flow collector were upgraded in the ranges of 14.62–16.94% and 31.19–37.72%, respectively using nano-coating. The mean specific energy consumption values were gained in the range of 4.18–4.53 kWh/kg. Moreover, energy efficiency values of the dryer were attained between 32.18 and 40.84% for the tested three configurations. It must be stated that the mean difference between experimental and numerical outlet air temperatures of the SAC was found as 6.2%. [ABSTRACT FROM AUTHOR]

Over the past years, there has been a huge growth in the solar energy research, development and progress, due to being a renewable, economical and non-polluting energy source. In this research, different design and placement of turbulators inside a cost-effective tube-type solar air heater (TSAH) has been analyzed to upgrade thermal performance. Both experimental and CFD analysis have been performed in order to survey the performance of solar heating systems. Numerical method has been done by utilizing Fluent program in order to simulate real models and also verified with experimental results. It is proposed to improve the thermal efficiency of TSAH by integrating turbulators in different modifications. According to the experimental outcomes maximum instantaneous heater efficiency was reached to 72.41%. Also, experimental and numerical average temperature difference values in TSAHs varied in the range of 9.16–14.54 °C and 9.50–14.95 °C, respectively. The experimental and numerical simulation results exhibited successful design of this simple and inexpensive alternative hot air generation system. Manufactured simple-structured TSAHs in the present work have acceptable thermal performance in comparison to more complex solar heaters in the literature. This type of solar heater could be used in different applications such as; drying, greenhouse heating, space heating and air preheating. • Investigation of integrating turbulators to tube-type solar air heater. • Numerical analysis and experimental validation for various solar air heaters. • Hollow, half-finned and full-finned heaters have been analyzed. • Thermal efficiency of cost-effective tube-type heater was reached 72.41%. [ABSTRACT FROM AUTHOR]

• Analyzing the effect of using nano-coating and infrared heater on the performance. • CFD analysis of three vertical solar heater (VSH) configurations. • Using ZnO nano-coating improved mean thermal efficiency of VSH between 21.13 and 21.62%. • Using infrared heater and nano-black paint reduced the drying time as 43.75%. In the present study, it is aimed to improve the performance of a solar drying system (SDS) utilizing ZnO nano-enhanced absorber coating and infrared heating system. In the first stage of this work, different geometrical configurations of the main heating system of the SDS which is a vertical solar air heater (VSH) have been numerically analyzed. According to the numerical findings, VSH with perforated type baffles gave the best performance results. Then, the determined configuration has been manufactured and combined with a drying chamber. Moreover, two other modifications have been applied to the system including an infrared heater and nano-enhanced black paint. In other words, the experimental part of this research contains three SDS types including a conventional SDS, a SDS with infrared heater and a SDS with infrared heater and ZnO nano-enhanced absorber coating (combined usage of two modifications). The mean thermal and exergetic efficiencies of the VSH analyzed within the scope of this work were attained between 53.54–65.12% and 9.94–14.32%, respectively. Moreover, combined use of infrared heater and nano-enhanced absorber coating material in the VSH decreased the drying time period as 43.75% when compared to the unmodified SDS. [ABSTRACT FROM AUTHOR]

• Numerical and experimental analysis of adding mesh modification to the absorber plate. • Iron mesh modification of absorber plate increased collector efficiency up to 10%. • Effect of mesh modification on the performance of double-pass indirect solar dryer. • Determination and comparison of quality characteristics as TPC, TFC and ABTS. In the present work, double-pass indirect solar dryer (DPISD) and double-pass indirect solar dryer with mesh absorber modification (DPISDMA) have been designed, analyzed, manufactured and tested. The main aim of this study is improving the thermal efficiency of double-pass solar air collector by integrating iron meshes. Pepino fruit (Solanum muricatum L.) samples in two thicknesses have been used in the experimental study. Also, CFD analysis of both solar air collectors and drying chamber and quality metrics such as phenolic, total flavonoid contents and antioxidant activity have been conducted. Numerical simulation and experimental results showed that using mesh modification has positive influence on the performance of the collector. The highest value of the average efficiency of the dryer was obtained in DPISDMA for the thin sample thickness as 23.08%. According to quality analyses, the experiments which done in DPISDMA gave the best results with highest values of TPC, TFC and antioxidant activity values (p < 0.05). Drying data of the pepino fruit for different experiments were modelled according to 8 different most used mathematical models. Accordingly, the best fitted kinetics model was determined as Logarithmic model for all experiments which gave the most accurate statistical values. [ABSTRACT FROM AUTHOR]

Solar water collectors are widely utilized for providing hot water to be used in different applications. In this work, a solar water collector with a helically coiled absorber has been designed, fabricated, and examined at different test conditions to specify its overall performance. One of the major goals of using a tube-type absorber is to upgrade the thermal efficiency of the collector by providing a perpendicular angle between the absorber and incident solar rays. Also, using a helically-coiled structure make it possible to increase the absorber surface in a relatively small volume in comparison to conventional solar water collectors. In the first step of this research, the designed helically-coiled solar collector has been simulated using a solar radiation model. In the next step, the manufactured helically-coiled solar collector has been experimentally tested at three different inclination angles and various water flow rates. According to the experimental results, mean thermal efficiencies of horizontal, vertical, and angular helically-coiled collectors were obtained in the ranges of 29.48–48.23%, 27.17–47.03%, and 32.50–52.71%, respectively. In addition, sustainability index values for horizontal, vertical and angular helically-coiled collectors were achieved between the ranges of 1.0041–1.0091, 1.0039–1.0087, and 1.0043–1.0102, respectively. Moreover, the maximum deviation between numerical and experimental findings was calculated as 14%. [ABSTRACT FROM AUTHOR]