Performance Of Solar Air Collector Research Articles

Enhancing thermo-hydraulic performance of solar air collectors through three-dimensional airflow using novel artificial roughness designs

BackgroundThe solar air collectors involve exploring their design, efficiency, and performance attributes. Common challenges include addressing issues such as small convective heat transfer coefficients between the air and the absorber, which can result to higher absorber plate temperatures and heightened thermal losses. Through the incorporation of artificial roughness onto the collector plate with a suitable design, it is possible to disrupt the shear layer and improve the convective coefficient. MethodsThis study focuses on hydrodynamic and thermal analyses to identify optimal chicane shapes and arrangements, such as CTPrism, CRRec, and CR, planted on the bottom wall of a solar air collector. Thermo-hydraulic performances are investigated using comprehensive CFD simulations, validated by experimental data and comparing them to smooth ducts. Significant findingsIn this work, a novel hydrodynamic and thermal analysis is introduced, demonstrating that the utilization of (CTPrism) shapes arranged in a staggered configuration leads to a significant enhancement of 68 % in heat transfer and 95 % in turbulent intensity. Consequently, there is an improvement in thermo-hydraulic performance, reaching up to 2.39, while still maintaining moderate friction losses.

Enhancing solar air collector performance through optimized entrance flue design: A comparative study

The current study examines the effect of entrance flue conditions on the performance of solar air collectors (SAC) with a single pass channel, focusing on two configurations: a front entrance solar air collector (FESAC) and a side entrance solar air collector (SESAC). The FESAC, introduced to optimise air distribution across the absorber plate, demonstrated higher performance, with higher outlet and lower absorber plate temperatures than the SESAC across various mass flow rates. The absorber plate temperatures for FESAC are 86 °C, 82.9 °C, and 75.1 °C, and for SESAC, 90.4 °C, 85.9 °C, and 79.1 °C for tested air flowrate 0.01118 (Case A), 0.01231 (Case B), and 0.01469 kg/s (Case C) respectively. Additionally, the maximum outlet temperatures for FESAC were 45.2 °C, 42.9 °C, and 39.5 °C for Case A, B, and C, respectively, while for SESAC, they were 43.1 °C, 41.4 °C, and 37.8 °C for the same cases. The study also emphasises a proportional relationship between airflow rate and collector efficiency. The observed daily efficiencies of the FESAC were 37.2 %, 40.4 %, and 44.4 % for the corresponding airflow rates mentioned above, while for the SESAC, they were 39.9 %, 43.4 %, and 47.5 % at these same rates. Additionally, the daily efficiency of the FESAC exhibited an enhancement of 3.1 % to 3.7 % relative to the SESAC, highlighting the effectiveness of entrance flue design in optimising SAC performance. These findings indicate the FESAC's enhanced capability in heat removal from the absorber plate and position the FESAC design as a promising avenue for boosting thermal efficiency in SACs. This study highlights the potential of modifying entrance flue configurations as a complementary approach to existing performance enhancement techniques for solar air collectors.

Investigation of solar air collectors with concave air duct

In this article study attempts to study the thermal performance of solar air collectors with submersible air ducts and pipes. This study is conducting numerical analysis of the solar collector with pin wings and turbulators to study the effects on the Nusselt number. The paper begins with a numerical analysis of conventional air collectors and compares them with theoretical results. Reynolds numbers range from 2000 to 2500. Next, after the solar collector's performance is evaluated with the bath air with channels, the effects of turbulators of different heights on the Nusselt number are analyzed, followed by the combined effects of pin wings and turbulators. The results are comparable to conventional solar collectors, and suggest that the combined effects of pin wings and turbulators can significantly improve the thermal performance of solar air collectors. The results of this study may contribute to the development of renewable energy-based air conditioning, ventilation and heating systems.

Multi-objective optimization design of solar air collector with a frustum-shaped protrusion

The artificial convex is arranged on the absorber plate of a solar air collector can significantly improve the solar utilization efficiency. The heat transfer efficiency is determined by the geometric types of protrusion and its arrangement in the heating channel. In this study, four parameters, the height and gap of the protrusion structure, the arrangement spacing of the V-shaped structure, and the airflow attack angle are considered to reflect the effect of protrusion on fluid flow and heat transfer characteristics in the solar air collector. Considering the interactive coupling relationship among various structure and location parameters, taking the maximum average Nusselt number, minimum friction coefficient, and maximum comprehensive heat transfer coefficient (THPP) as the objective functions, the Response Surface Method (RSM) is adopted to comprehensively analyze the impact of multiple factors on the thermal efficiency of solar air collector, and thus obtains the optimal design parameters of solar air collector with the optimal comprehensive performance. Comparing with the univariate method, the THPP value of the optimized structure by RSM is 3.6% higher than that by the univariate method. The value of thermal efficient of the optimized structure by RSM is 26% higher than that of the smooth plate solar air collector. When the Reynolds number is higher than 10000, the value of thermal efficient of the optimized structure by RSM is much higher than those of the published references. In addition, the contribution of different influencing factors to improving the comprehensive performance of solar air collector was obtained, which is meaningful for providing theoretical basis for engineering optimization design.

Employing a fan to improve the wintery heating performance of solar air collectors with phase-change material: An experimental comparison

Solar Air Collectors integrated with Phase-Change Material (SAC-PCM) were widely used for wintery heating with the superiority of overcoming the mismatch shortcoming between supply and demand time from solar heating. However, the traditional SAC-PCM had the low-efficiency heat output due to the low air flow of natural convection. Based on this, a fan was proposed to enhance air flow and thereby, increase the heat output from SAC, so an experiment was built to compare the thermal performance between SAC-PCM and SAC-PCM with a fan (SAC-PCM-F). The experimental result showed that the fan enhanced the outlet wind speed from 0.8 m/s-1.55 m/s to 2.15 m/s-2.3 m/s and by employing the fan, the heat output was easier from SAC-PCM and the average temperatures of outlet air were increased 4.18 °C in all day with the average temperature difference of outlet and inlet air increased by 1.17 °C. Employing the fan could improve indoor average temperature by 1.17 °C, while the daily heat output was increased by 146.02% by employing the fan and the heat collecting efficiency was increased from 24.92% to 61.32%

Investigation of Solar Air Collectors with Carbon-Nanotube-Based Turbulators and Pin Fin Arrangements

This research attempts to investigate the thermal performance of solar air collectors with pin fins and turbulators. Incorporating carbon-nanotube-based fins and turbulators in solar collectors can enhance their performance due to their high thermal conductivity, low weight, and high aspect ratio. In the present study, numerical analyses of a solar collector with pin fins and turbulators are carried out to investigate its effect on the Nusselt number. The paper begins with the numerical analysis of conventional air collectors and compares them with theoretical results. This is followed by numerical analyses, which are carried out to examine different configurations of the absorber plate with pin fins of varying diameters (10 mm, 20 mm, and 30 mm) and turbulators of varying heights (20 mm, 40 mm, and 60 mm) in the base plate. The analyses include variations in the Reynolds number ranging from 3000 to 15,000. Subsequently, after the performance of the solar collector with pin fins is evaluated, the effect of turbulators of varying heights on the Nusselt number is analyzed, followed by the analysis of the combined effect of pin fins and turbulators. The results are compared with traditional solar collectors and show that the combined effect of pin fins and turbulators can significantly improve the thermal performance of solar air collectors. The findings of this study can contribute to the development of renewable energy-based air conditioning, ventilation, and heating systems.

Experimental investigation of thermal performance of single pass solar collector using high porosity metal foams

The previous literature showed that there have been many studies focusing on some specific aspects of single-pass solar air collectors, such as the effects of the number of passes, the shape of fins, and their effects on thermal performance. Also, the effect of thermal efficiency accompanied by the existence of these fins has been the interest of many studies. A few research types are dealing with using porous materials (Metal foam) to improve thermal performance. Therefore, an experimental apparatus was designed and fabricated to study the effect of Metal Foam (MF) on the performance of solar air collectors. The experiments were held in Iraq, Al Ramadi climate conditions. A comparison of three configurations of absorber plates of solar air heaters with and without MF is presented and evaluated. The results showed that by including MF fins in the absorber plate, the absorber plate's surface area was increased, increasing heat transmission compared to a flat plate (without MF). Moreover, utilizing MF at the tilted angle of 45° (MFθ=45o) increased turbulence intensity, which improved the mixing of cold and hot air. The MFθ=45o layout had the best thermal efficiency of the three employed configurations (94.8%), followed by the MFθ=0o configuration (62.6%) and the flat plate configuration (33.8%), all with the same mass flow rate. Finally, when using MF fins with a tilted angle of 45°, the air temperature differential is bigger compared to MF fins with a tilted angle of 0° or a flat plate collector.

Review of methods for improving the thermal performance of solar air collectors with flat plates

The latest research on improving the thermal efficiency of flat solar air collectors is carried out on the modification of the absorber surface, the organization of multiple air flow, the use of porous absorbers, the transfer of air flow to the absorber surface by impact, the integration of the absorber surface with heat accumulating materials. The formation of a laminar viscous layer on the surface of the absorber leads to the deterioration of heat transfer to the air stream. The main factor for increasing the heat transfer in flat solar air collectors is to increase the heat transfer surface and the air residence time in the collector, which is achieved by using fins, barriers, turbulizers and baffles. When installing turbulizers of different shapes on the surface of the absorber, the thermal efficiency of the collector increases from 71.4% to 93%. When the absorber surface is integrated with heat-accumulating materials and ribs, the daily thermal efficiency of the collector increases to an average of 0.4-4%. This review article presents an analysis of the scientific research conducted in the last decade on improving the thermal efficiency of flat solar air collectors.

The effect of closed cycle of air flow circulation on the thermal performance of solar air collector

The effect of closed cycle of air flow circulation on the thermal performance of solar air collector

Thermal Performance Analysis of a Double-Pass Solar Air Collector: A CFD Approach

Solar air heaters can reduce climate change by replacing conventional fossil fuel-burning technologies in drying and space heating applications. Concentrating solar technologies, such as compound parabolic concentrators, allow air temperatures up to 120 °C; however, it is desirable to improve their heat transfer to reduce the space requirements for their installation. In this work, a parabolic concentrator composed of a flat receiver designed to recover heat from the cover–receiver–reflectors cavity is analyzed, operating it as a U-shape double pass solar heater. With this operation, first, the air flows through the cavity, and then it is incorporated into the duct, where the dominant heat gain occurs due to the capture of solar radiation. Thus, four input–output configurations in the cavity were modeled through dynamic simulations to determine the influence of the inlet and outlet air flow positions on the solar concentrator outlet temperature. Therefore, the incorporation of the first pass has a contribution of between 36% and 45% in useful energy gain, showing that this appropriate and relatively simple strategy can be implemented to improve the thermal performance of solar air collectors, resulting in instantaneous efficiencies higher than 75%. However, the simulation results demonstrate that the position of the inlets and outlets does not significantly impact the efficiency and outlet temperature.

Design a low-cost, medium-scale, flat plate solar air heater: An experimental and simulation study

The most efficient solar air heater is expensive, and attempts to reduce costs lead to reduced efficiency. The current study presents a low-cost, medium-scale, flat plate solar air heater's design, simulation, and experimental thermal analysis. Carbon steel, thermocol, window glass, and aerosol spray paint were utilized for fabrication to decrease manufacturing costs. Initially, a mathematical model was developed, and experimental tests on this system were carried out with different absorber plates and glass covers in various weather conditions. The air mass flow rate of the collector is set at 0.073 kg/s. According to the experimental results, the solar air collector with a finned steel absorption plate, black paint, and double-glazing exhibit optimal performance. Under average solar radiation and ambient temperature of 910 W/m2 and 29.44 °C, respectively, the maximum thermal efficiency is 60.81 %, the average thermal efficiency is 56.01 %, and the average air temperature difference between the inlet and outlet is 40 °C. Whereas, for the solar air collector with plain steel absorber plate and single glazing, the least desirable performance was observed with a maximum collector efficiency of 45.76 %, an average thermal efficiency of 39.22 %, and an average air temperature difference of 20.14 °C between inlet and outlet under average solar radiation and ambient temperature of 810 W/m2 and 29.98 °C, respectively. Compared to the results, the thermal performance of solar air collectors with a finned steel absorption plate, black paint, and double-glazing was improved by 14 % to 20 % under different conditions. In addition, the solar air heater was designed, and a simulation study was performed in COMSOL Multiphysics software to find the temperature distribution of the glass cover and absorber plate. The experimental findings demonstrated that this convenient and cost-effective solar air collector was designed successfully and can be utilized in heating applications.

Thermal performance enhancement of solar air heater using louvered fins collector

Solar air heater is one of the important device for heating the air which is mainly used for space heating, timber seasoning, crop/vegetable drying, etc.. To improve the performance of solar air collectors, the fin plays an important role to increases the performances. Due to this reason in the present work, a novel type of solar air heater has been constructed with louvered fins and performed experiments to evaluate its thermal performance. The louvered fins have been attached to the bottom of the absorber plate to steer the flowing air and increase the heat transfer rate. To achieve this aim, the solar collector has been designed with the value of louvered angle, louvered length, louvered pitch & height taken to be 20°, 2.5 cm, 2.5 cm, and 3.5 cm, respectively, and conducted experiments with mass flow rate 0.007 kg/s to 0.0158 kg/s. The variations of insolation and fin spacing on the thermal efficiency and temperature rise have been also studied in the present experimental study. The results indicate that thermal efficiency increase with increasing flow rate, for a mass flow rate of 0.0158 kg/s and 0.007 kg/s, thermal efficiency and outlet temperature obtained a maximum of 70% and 58.66 °C respectively for spacing of 2 cm. further, observed that the thermal efficiency of louvered fin spacing 2 cm and 5 cm is higher as compared to plane solar air heater which is 106.7% and 59.45% respectively. The thermal performance of the louvered fins solar air heater is significantly enhanced as compared to that of the plane solar air heater.

Exploration of the effect of two-axis PLC solar tracking system on the thermal performance of solar air collector

In the present study, the effects of a solar tracking system on the thermal performance of the solar air collector (SAC) were investigated in detail. Two SACs of equal size were designed to reveal the effect of the solar tracking system. One of the SACs was fixed at 38° South-East; on the other SAC, two-axis PLC solar tracking system was integrated. Thermal efficiency analyses were carried out for both SACs at three different airflow rates under the same environmental conditions. While the highest energy efficiency value was calculated as 86% for the movable SAC, the lowest energy efficiency value was calculated for the fixed SAC as 14%. It was determined that the average exergy efficiency value of the movable SAC is 2.8 times higher than the exergy efficiency value of the fixed SAC. In addition, it was shown that the average SAC input-output temperature difference was increased by two times with the help of the solar tracking system. Also, according to the economic analysis, it has been observed that the movable SAC was two times more environmentally friendly than the fixed SAC. Additionally, it was revealed that the movable SAC has 2.13 times more heat transfer value than the fixed SAC. In addition to all these, Nu values obtained for three different mass flow values in SAC were compared with different Nu correlations in the literature, and it was shown that the experimental Nu values were compatible with these correlations. According to the experimental data, it was clearly stated that the solar tracking system significantly improves the thermal performance of the SAC.

Experimental and Numerical investigation of implementing a novel vortex generator: A Perforated Delta Wing Vortex Generator (PDWVG) on the performance of Solar Air Collector

Experiments were carried out for the numerical investigation of heat transfer enhancement in a solar air collector using different types of baffles and vortex generators. In this study, the vortex generator was implemented to increase the efficiency of the solar air collector. The variations in Nusselt number, pressure drop, friction coefficient, thermal and exergy efficiency in four collectors with different baffles arrangement (type A, B, C, D) were investigated. Type A was chosen as the optimum collector for implementing the vortex generator on the absorber surface. In the solar air collector the effects of using a novel vortex generator - the Perforated Delta Wing Vortex Generator (PDWVG), in comparison with a flat one - the Flat Delta Wing Vortex Generator (FDWVG), were considered. In order to determine the maximum efficiency of the solar air collector, four different pitch ratios of vortex generators were studied. The Nusselt number and pressure drop increased with Reynolds number but the friction coefficient decreased with Reynolds; the experimental and numerical results revealed that the thermal and exergy efficiency decreased from a specific range. The comparison of PDWVG and FDWVG showed that presence of holes on the novel vortex generator, led to reduced pressure drop and increased the heat transfer between the air flow and the absorber surface. Increasing the number of vortex generator rows had a slight effect on increasing the studied parameters. The results showed that collector type A with ep=0.55 of PDWVG improves the energy and exergy efficiency 4.43% and 5.29% respectively.

Experimental analysis and exergetic assessment of the solar air collector with delta winglet vortex generators and baffles

To increase the efficiency of solar air collectors (SACs), the combined effects of baffles and delta winglet vortex generator (DWLVG) on the performance of SAC have been investigated. An experimental setup has been made, and numerical simulation is carried out in Ansys Fluent. The numerical investigation is validated by the experimental study and focused on the number of baffles as well as the number and the height of DWLVG. The results show that the SAC with no baffles and DWLVG has the lowest efficiency with the maximum value of 13%, while for SAC with six baffles and three pairs of DWLVG, the efficiency reaches up to 20%. The exergy analysis of three cases, SAC without baffles and DWLVG, SAC with six baffles without DWLVG, and SAC with six baffles and three pairs of DWLVG, shows that the maximum exergy efficiency of the SAC is 30.44% and occurs when the height ratio and the number of DWLVG pairs are 0.5 and 3. The results show that for SAC with six baffles and three pairs of DWLVG, the energy and exergy efficiency improve 7.4% and 12% on an average basis compared to the typical flat plate SAC, respectively. This improvement in thermal and exergy efficiency is due to the implementation of DWLVG which produces more turbulence and eliminates the vortices generated at the corners of SAC.

Thermo-Hydraulic Performance of Solar Air Collectors with Artificially Roughened Absorbers: A Comparative Review of Semi-Empirical Models

Due to the poor thermal characteristics of the air, the absorber roughness of solar air collectors is commonly artificially increased in order to enhance the heat transfer to the air stream. However, this is also accompanied by an undesirable increase in the pumping power due to increased friction losses. As a result, several authors have experimentally investigated several ways of maximizing the heat transfer while minimizing the friction losses of different absorbers, resulting in the development of semi-empirical functions relating the Nusselt number (a measure of heat transfer) and the friction factor (a measure of friction losses) to the Reynolds number and the roughness parameters considered for each absorber. The present paper reviews, considering the publications from the last ten years, these semi-empirical functions. Moreover, the optimum roughness parameters and operating conditions of the absorbers were estimated by finding the maximum values of two performance parameters (the thermo-hydraulic efficiency and effectiveness), calculated using the semi-empirical functions, in order to classify the absorbers in terms of their energy characteristics. This approach proves to be a rather effective way of optimizing the roughness characteristics of solar air collector absorbers. It is also concluded that, considering the range of absorbers analyzed here, generally, multiple V-shaped ribs with gaps provide the most effective roughness geometry.

Experimental and Numerical Study of a New Corrugated and Packing Solar Collector

The thermal performance of a new solar air collector with corrugated packing is studied in this work. A new innovate shape was suggested in this paper to improve the thermal performance of the solar air collector. Mathematical models are developed to investigate the thermal performance of the collector and the results are verified by experiments. Effects of the operating parameters, solar radiation intensity and inlet air velocity are studied to optimize the thermal performance of the collector. Comparisons are conducted between the experimental and numerical results and good agreement was found. The new innovate shape shows better performance than other corrugated shapes and the absorber and air gained higher temperatures. The maximum temperature of air inside duct at the exit point was 69.1 C° at solar heat flow of 725 W/m2 and inlet velocity 1.0 m/s. The new shape shows better performance than other corrugated absorber.

Vacuum Effect on the Performance of Solar Air Collector with Micro-Channel Absorber Plate

Vacuum Effect on the Performance of Solar Air Collector with Micro-Channel Absorber Plate

Exergy analysis of single‐flow solar air collectors with different configurations of absorber plates

AbstractIn the current study, an experimental analysis of exergy performance for different absorber plates is done. Three types of absorber plates are supplied with different fin arrangements with a variable air mass flow rate. The exergy analysis to evaluate the exergy performance of the solar air heaters uses experimental data for conventional and finned solar air collectors with different arrangements of fins. The main aim of the current study is to compare the exergy performance of the conventional solar air collector with those equipped with fins. The introducing of the fins in different arrangements enhances the absorber surface area, which leads to increased heat transfer. Also, fins induce air turbulence in the flow field, which improves the exergy performance of solar air collector. It is found that the exergy reduces and exergy efficiency enhances with increasing the airflow rate. The traditional flat absorber plate has undesirable exergy loss and exergy efficiency for all ranges of airflow rates. Thus, the flat plate collector presents the most substantial irreversibility, for which the exergy efficiency is the least. However, the results show that the exergy efficiency of inclined staggered turbulators is higher than that of in‐line and staggered turbulators. The optimal value of exergy efficiency is recorded at nearly 77% for the solar air collectors equipped with inclined staggered turbulators compared with other types of configurations.

Investigative study of the thermal performance of a trial solar air heater

Solar collectors need to be inclined at the optimum angle to maximize the receiving energy. The evaluation of the thermal performance of solar air collectors is important for the proper design and sizing of the collector for a given application. In our experimental/theoretical study, which consists of a thermal performance investigation, we have sought to optimize the efficiency–temperature rise couple of the designed solar air heater by considering the appropriate assembling materials regarding the absorber, the glazing and the insulation. Obviously, efficiency is dependent on the orientation of solar collectors and the measured parameters climate conditions such as wind speed, solar radiation and ambient temperature. In order to achieve possible performance optimization of the receiver plane using a low number of variables and equations, the calculations were carried out considering four values of azimuth angle, γ = 0°, 22.5°, 45° and 67.5°, and by varying the tilt angle β by 5 degrees from 15° to 70°.