Performance Of Solar Air Heater Research Articles

Effect of Chamfered Turbulators on Performance of Solar Air Heater - Numerical Study

This paper presents a numerical analysis of the thermal performance improvement in a flat plate solar air heater equipped with chamfered turbulators attached below the absorber plate for evaluating performance for Reynolds numbers ranging from 3,000 to 21,000. According to the research, chamfered turbulators caused the flow to become highly turbulent. This flow behaviour with flow separation around the turbulators positively affects performance. This paper attempts to explain the complex flow behaviour found during the analysis. The turbulator diameter varies in 1 mm increments from 3 to 7 mm at a constant longitudinal pitch of 200 mm. The number of turbulator rows in the transverse direction is kept constant at three. The chamfer is represented by the flow attack angle, which can be 30°, 45°, or 60° facing the direction of flow and opposing the direction of flow. The results showed that a 7mm diameter turbulator with a 30° chamfer angle placed against the flow of air yielded a considerably more significant thermal enhancement factor of 1.15 over the spectrum of flow Reynolds number studied

Effect of Chamfered Turbulators on Performance of Solar Air Heater - Numerical Study

This paper presents a numerical analysis of the thermal performance improvement in a flat plate solar air heater equipped with chamfered turbulators attached below the absorber plate for evaluating performance for Reynolds numbers ranging from 3,000 to 21,000. According to the research, chamfered turbulators caused the flow to become highly turbulent. This flow behaviour with flow separation around the turbulators positively affects performance. This paper attempts to explain the complex flow behaviour found during the analysis. The turbulator diameter varies in 1 mm increments from 3 to 7 mm at a constant longitudinal pitch of 200 mm. The number of turbulator rows in the transverse direction is kept constant at three. The chamfer is represented by the flow attack angle, which can be 30°, 45°, or 60° facing the direction of flow and opposing the direction of flow. The results showed that a 7mm diameter turbulator with a 30° chamfer angle placed against the flow of air yielded a considerably more significant thermal enhancement factor of 1.15 over the spectrum of flow Reynolds number studied

Effect of Channel Depth Ratio and Absorber Plate Configuration on Performance of a Solar Air Heater

An experimental evaluation of the effect of channel depth ratio and absorber plate configuration on the performance of a baffled counter flow double-pass solar air heater (BCDSAH) is main objective of current work. The BCDSAH was constructed so as to permit adjustments of channel depth ratio (CDR) to 2, 3 and 4. During experimentation, the lower channel depth was kept at 50 mm while the upper channel depth was adjusted to 100 mm, 150 mm and 200 mm, yielding various channel depth ratios. The assessments were conducted for three configurations of absorber plate: (i) flat absorber plate, (ii) baffled absorber plate and (iii) baffled absorber plate with phase change material (PCM). The performance of the BCDSAH was evaluated at an air mass flow rate of 0.07 kg/s for temperature rise, useful heat gain (UHG), energy efficiency, and exergy efficiency. For CDR = 2 and a baffled absorber plate with PCM, the obtained average values of temperature rise, UHG, energy efficiency and exergy efficiency were 15.3 oC, 1075.2 W, 76.2% and 2.7% respectively. For the baffled absorber plate with PCM, increases of 8.5%, 9.4%, 10.1% and 10.9% were obtained in temperature rise, UHG, energy efficiency and exergy efficiency respectively for CDR = 2 compared to CDR = 4. Finally, a value of CDR = 2 and a baffled absorber plate with PCM are suitable for applications like drying of agricultural products and space heating.

Enhancing performance in solar air channels: A numerical analysis of turbulent flow and heat transfer with novel shaped baffles

Solar air heaters are emerging as a promising solution for sustainable heating, as they harness abundant solar energy to provide heat for a variety of applications. However, their optimum efficiency remains a major challenge. Deflectors have significant potential to improve the performance of solar air heaters by redirecting airflow and optimizing heat transfer, making them more efficient and more suitable for large-scale adoption. This article examines the performance of a new baffle design aimed at improving heat transfer in the channel by increasing the exchange surface between fluid and solid surface. It consists of a “≠” -shaped baffle mounted on the top and bottom walls of the channel. An in-depth analysis of the spacing between these baffles was carried out to assess their impact on the thermal and aerodynamic properties of the solar air channel. Computational Fluid Dynamics (CFD) was used to perform the calculations, using the Finite Volume Method (FVM) in conjunction with the SIMPLE algorithm. All studies are carried out using the CFD code Fluent. Crucial steps in this research include studying the influence of these new baffles at different Reynolds numbers, ranging from 15000 to 35000, as well as varying the separation distance between the two baffles, chosen periodically (DBaffle/2, 3DBaffle/4, DBaffle, 5DBaffle/4 and 3DBaffle/2). Some of the numerical results were validated with the available experimental data and showed satisfactory agreement. The study identified an optimal case for the new baffles, by reducing the distance between the baffles, an improvement in system performance was observed, by increasing the flow strength and widening the recycling cells, which has an impact on dynamic behavior and heat transfer. The presence of this new baffle design, with minimal separation distance between them, demonstrated a significant thermal improvement, with a thermal improvement factor increasing by 44% compared to the simple channel without baffles, thus highlighting the effectiveness of the new solar air channel with “≠” -shaped baffles.

Effect of the baffle's type on thermal performance of solar air heaters

To determine the optimal baffle's type (longitudinal and transverse baffles) and the number of baffles, two computational fluid dynamics (CFD) models for solar air heaters (SAHs) were developed by using "ANSYS Fluent" software. The computational results closely aligned with the experimental data. As the width of the air channel in SAHs with transverse baffles was narrower than in those with longitudinal baffles under the same number of baffles, the heat transfer coefficient of SAHs with transverse baffles was greater than those with longitudinal baffles. Thus, for the airflow rate (m˙) range of 0.013 kg s−1 to 0.078 kg s−1, SAHs with transverse baffles exhibited 2.34 %–6.97 % higher collection efficiency compared to those with longitudinal baffles. An analysis of the impact of the number of transverse baffles (N) on the flow and heat transfer characteristics in SAHs revealed that both the size and intensity of the vortex zones increased with an increase in N, thereby influencing the heat transfer between the air and the absorber plate. Specifically, among the studied values of N (2, 4, 6, and 8), at = 0.026 kg s−1, N = 4 achieved the peak effective efficiency at 54.32 %. Conversely, for m˙ = 0.039 kg s−1, 0.052 kg s−1, 0.065 kg s−1, and 0.078 kg s−1, the highest effective efficiency was observed at N = 6, with values of 60.03 %, 63.78 %, 64.39 %, and 64.38 %, respectively.

Optimizing of a metal foam-assisted solar air heater performance: a thermo-hydraulic analysis of porous insert placement.

A numerical assessment of the heat transfer efficacy of a solar air heater (SAH) was carried out. The SAH is supplied with a porous metal foam layer to improve thermal mixing. Both the local thermal non-equilibrium (LTNE) and Darcy-extended Forchheimer (DEF) models were employed to forecast fluid and thermal transport within the partly filled SAH channel. The analysis was performed for various values of dimensionless foam layer lengths ( ), pore densities ( ), and Reynolds numbers ( ) at a fixed value of layer thickness ( ). Based on the position of the porous layer, three distinct arrangements, marked as Case 1, Case 2, and Case 3, were explored. Regarding the parameters examined, the findings indicate a definite improvement in the average Nusselt number ( ), but unfortunately, the friction factor also increases unfavorably. By reducing the length of the porous layer, a reasonable reduction in heat transfer rate and a significant decrease in pressure drop were noticed. The results showed about 26.64%, 48.73%, and 70.74% reductions in pressure drop by reducing the dimensionless foam length from 1 to 0.25, 0.5, and 0.75 respectively for at . On the other side, there are only about 11.05%, 23.11%, and 40.78% reductions in . The exhaustive analysis of the thermal performance of SAH was conducted using the thermal performance factor (TPF), which considers the trade-off between the SAH channel's potential for improved heat transmission and its cost for pressure loss. The TPF may reach a maximum of 2.82 compared to the empty channel when the metal foam layer is inserted with , for , and .

Numerical assessment of solar air heater performance having a broken arc and broken S-shaped ribs as roughness

This research article aims to provide a detailed numerical study of the multifaceted impact of S-shaped and broken arc roughness on solar air heaters. Therefore, a strong comparison was made between the modified heaters and smooth heaters for Reynolds numbers ranging from 2 00022 000. Also, the impact of two parameters, i.e. pitch and gap was analyzed to optimize the performance of the heater. The gap varies from 0.3 mm to 0.9 mm in both types of ribs with a step size of 0.2 mm. Afterwards, the pitch distance between both types of roughness was varied from 15 mm to 25 mm in the step size of 5 mm. Notably, it has been observed that among all the considered configurations, the gap length of 0.9 mm and pitch length of 25 mm have shown significant improvements in heat transfer characteristics. The specific combination of the gap of 0.9 mm and pitch of 25 mm has demonstrated better heat transfer capabilities at the expense of an increased friction factor. Lastly, the thermal performance factor of the systems was analyzed and reported. It was reported that the pitch length of 25 mm and gap length of 0.9 mm have shown a maximum thermal performance factor value from 2.9 to 3.3, while the pitch length of 25 mm and gap length of 0.3 mm have depicted the lowest thermal performance factor value. In terms of the overall performance, i.e. the thermal performance factor, the combination with a gap of 0.9 mm and pitch of 25 mm has shown the best performance, while a gap of 0.3 mm and pitch of 25 mm has yielded the worst performance.

Experimental and meta-heuristic optimization for the highest thermo-hydraulic performance of a solar air heater with a V-notch pattern of hemispherical protrusions on absorber surfaces

Thermo-hydraulic performances of a new solar air heater with single V-notch patterns of hemispherical protrusions on the absorber plate are investigated experimentally for different relative protrusion heights (hp/Dh = 0.027–0.069), relative pitch (pp/hp = 6–14), attack angle (αap = 15°-75°), and Reynolds number (Re =3600–21,700). Three meta-heuristic algorithms, i.e., Ant colony optimization (ACO), Whale optimization algorithm (WOA), and Grass-hopper optimization algorithm (GOA), were used for single and multi-objective optimizations. Experimental results provide the maximum Nusselt number (Nu) as 127.07 at hp/Dh = 0.050, pp/hp = 10, αap = 600, and Re =21,700, whereas the minimum friction factor (f) becomes 0.0165 at hp/Dh = 0.027, pp/hp = 10, αap = 450, and Re =21,700. The highest normalized Nusselt number (Nu/Nus) is found to be 2.56 for hp/Dh = 0.050, pp/hp = 10, αap = 600, and Re =7200, and the maximum normalized friction factor (f/fs) is observed as 4.30 at hp/Dh = 0.050, pp/hp = 10, αap = 450, and Re =7200. The highest thermo-hydraulic performance parameter (THPP) was to be 1.60 at pp/hp = 10, hp/Dh = 0.050, αap = 600, and Re =7200. Empirical correlations were developed. In single objective optimization for Nu, WOA provided the best results. For f, WOA gives a minimum value. The WOA metaheuristic algorithm outperformed the other algorithms.

Thermo-hydraulic performance of solar air heater with built-in one-eighth sphere vortex generators

The primary objective of optimizing solar air heaters is to enhance their thermal efficiency, and the incorporation of perturbing elements into the absorber plate has proven to be an effective approach. The present study employed an electric heating plate to simulate solar heating and proposed a novel one-eighth sphere vortex generator to create strong longitudinal vortices and weak transverse vortices, thereby achieving enhanced overall performance. The experimental investigation focused on examining the impact of parameters, including deflection angle (α), relative transverse pitch (S/H), relative longitudinal pitch (L/H), relative height (e/H), and Reynolds number (Re), on both heat transfer and flow characteristics. The results show that new vortex generator performs best at deflection angles of 180°. The maximum thermo-hydraulic performance parameter of 2.03 was observed in this study. Additionally, it was found that the maximum Nusselt number (Nu) and friction factor (f) were 2.45 and 1.96 times higher than those obtained for a smooth duct, respectively. New correlations of Nusselt number (Nu) and friction factor (f) were developed to predict the heat transfer and flow resistance characteristics of solar air heater with built-in one-eighth sphere vortex generators. This study proposes a new idea to enhance the performance of solar air heaters.

Outdoor performance investigation of a thermoelectric cooler-integrated solar air heating collector

Solar air heating systems are continuously being improved by combining them with other energy conversion technologies. In this paper, outdoor tests were carried out on a thermoelectric heat-pumping solar air heater (TE-SAH), with four (04) TECs (TEC1–12706) attached to the backside of the absorber plate, and powered by a 40Wp mono-Si PV module to pump heat from the absorber plate into the heated air. The thermal energy production, energy efficiency, heat loss coefficients, and heat removal factor were evaluated and compared with a reference system without TECs. The heat collection and energy efficiency of the solar air heater were improved by 7.14 % and 66.71 %, respectively, with the integration of TECs. Heat losses also decreased by 0.46 MJ. Furthermore, the estimated heat removal factor for the TE-SAH was 0.55, higher than 0.49 obtained for the reference SAH. These results showed that PV-TE heat-pumping is a viable means of improving the thermal performance of solar air heaters.

Assessing the effects of different finned absorbers with swirl flow on the performance of solar air heater

ABSTRACT In this study, the effects of various absorber configurations of a tubular solar air heater are investigated. The models such as direct flow with a standard absorber (DF-SA), swirl flow with a standard absorber (SF-SA), swirl flow with perforated longitudinal fins (SF-PLF), swirl flow with radial fins (SF-RF), swirl flow with perforated radial fins (SF-PRF) are studied. Investigation parameters including Nusselt number, exergy efficiency, PEC, and friction factor are examined with Reynolds numbers ranging from 8488 to 25,464. The findings reveal an enhancement in Nusselt number, PEC, and exergy efficiency corresponding to an increase in Reynolds numbers, while the friction factor decreases. Models employing air-swirl flow entrances demonstrate superior effects in improving the performance compared to direct flow inlets. Notably, the SF-PRF shape records the maximum Nu ratio of (102.5–108%). This model has the maximum values of PEC enhancement ratio of (103.9–106.2%) compared to DF-SA, indicating the enhancement obtained by using swirl flow with perforated ring fins. Analysis of streamlines and distributions of temperature, pressure, and velocity elucidates the effects of perforated radial fins on vortex generation and secondary flow, particularly when incorporating air swirl inlets.

Enhancing solar air heater performance through pin–fin absorber plates and tailored MWCNT coatings: a comprehensive comparative analysis

Enhancing solar air heater performance through pin–fin absorber plates and tailored MWCNT coatings: a comprehensive comparative analysis

Numerical investigation of heat transfer and thermo-hydraulic performance of solar air heater with different ribs and their machine learning-based prediction

Numerical investigation of heat transfer and thermo-hydraulic performance of solar air heater with different ribs and their machine learning-based prediction

EFFECTIVE EFFICIENCY ANALYSIS OF ARTIFICIALLY ROUGHED SOLAR AIR HEATER BY DIAGONALLY CHAMFERED CUBOID ARRAY

The solar air heater (SAH) is a very simple and economical device, but its thermal performance is quite poor. Boosting the heat transfer between absorber plates and the airflow can improve the thermal performance of a solar air heater. Applying artificial roughness to the absorber plate is a unique method for improving the thermal performance of solar air heaters compared to other methods. In this study, diagonally chamfered cuboids were utilized as roughness elements to investigate the enhancement of the performance of a solar air heater. This roughness is achieved by attaching diagonally chamfered cuboids to the absorber surface. A thorough experimental investigation was carried out to examine how this roughness affects the performance of solar air heaters. The study considered several parameters, such as relative roughness pitch (RRP) (5 to 8), arm length of cuboid (ALC) (4 to 10 mm), and relative roughness height (RRH) (0.44 to 0.077). To ensure turbulent flow during the experiment, the Reynolds number was kept within the range of 4250 to 18,000, which is considered ideal for solar air heaters operating with a constant heat flux of 1000 W/m<sup>2</sup> on the absorber plate. An overall performance assessment of the artificially roughened solar air heater was conducted, which included analyzing the Nusselt number and friction factor for both roughened and smooth absorber surfaces operating under similar flow conditions. The maximum Nusselt number achieved was 3.68 times higher than that of the smooth absorber plate at Re = 4250, with roughness parameters RRP = 5, RRH = 0.077, and ALC = 10. The analysis also reveals a 2.48-fold improvement in the overall performance of the roughened configuration.

Review on different techniques used to enhance the thermal performance of solar air heater

Energy is the key driver of life. It is required for the growth, exaltation, modernization, and financial development of any country. The world is turning away from fossil fuels in favor of renewable energy sources in order to meet the rising demand for energy and protect the environment from pollution. Solar energy is becoming a significant source of energy among these new energy sources. The primary solar energy-using appliances are solar air heaters. However, the creation of a laminar sub-layer on the absorbing plate is the cause of its poor thermal efficiency, which is a cause for concern. This paper describes various techniques through which the efficiency of solar air heaters (SAH) is enhanced by disturbing the laminar sub-layer. This study is concentrated on four techniques artificial roughness, jet impingement, piezo-electric fan, and phase change material (PCM), which are explained in four sections. The first section gives a detailed description of artificial rib roughness, turbulators, and protrusions. The second section reviews the use of jet impingement in SAH. The third section introduces a new technique; a piezo-electric fan and describes its mechanism, working parameters, and possibilities for its use in SAH through the previous studies. The fourth section reviews the use of PCM material in SAH by the previous studies. The maximum thermal hydraulic performance factor (THPP) for non-circular ribs, ribs with a rectangular cross section, ribs with an equilateral cross section, and jet impinged SAH, respectively, has been observed to be 1.44–1.29, 2.19, 2.11, and 3.66.

Employment of roughened absorber palate and jet nozzles with different hole shapes for performance boost of solar-air-heaters

In this study, roughened absorber plate and jet nozzle are simultaneously employed to enhance the efficiency of a solar based air heater. The impact of jet nozzle hole shape is comprehensively investigated for the mentioned system which have not been investigated before. Three-dimensional steady-state simulations of incompressible turbulent fluid flow and heat transfer are performed using the Reynolds-Averaged Navier-Stokes (RANS) equations to model the jet solar air heater (JSAH). Five different jet hole shapes (circular, triangular, square, hexagonal, and rectangular) are examined and results are compared with conventional structure. The thermal and hydraulic performance of the JSAH is assessed using a variety of geometric and operating parameters, including jet diameter ratio (dj/Dh), jet hole streamwise pitch (Lj/Dh), and Re number (Re). The results show that the ratio of (Nu/Nus) initially increases and then decreases as the hydraulic diameter of the jet holes increases. Circular jet holes consistently outperform other shapes, while rectangular and triangular jet holes perform poorly. The pressure penalty (f/fs) decreases with increasing (dj/Dh), with circular jet holes exhibiting the lowest value. Increasing the Reynolds number enhances heat transfer and pumping power but leads to a decrease in (Nu/Nus) and negatively affects the THPP of the JSAH compared to a conventional smooth solar air heater. The study also reveals that the THPP initially increases with streamwise pitch (Lj/Dh) but then declines, following the trend of (Nu/Nus). The results demonstrate up to 4.5 times higher Nusselt numbers with a jet solar air heater versus a smooth solar heater. A maximum thermal-hydraulic performance parameter of 1.64 indicates the proposed design's efficacy. This research furnishes critical insights into optimizing solar air heater performance by examining jet nozzle hole shape, streamwise pitch, and Reynolds number. It enables enhancing thermal efficiency and thermo-hydraulic performance.

Experimental Analysis of a Solar Air Heater Featuring Multiple Spiral-Shaped Semi-Conical Ribs

Abstract To improve the thermal and hydraulic performance of artificially roughened solar air heaters (SAHs), the current study analyzes the thermal-hydraulic performance or thermal enhancement factor of artificially roughened solar air heaters. In present experimental research on a solar air heater's absorber plate, newly designed spiral-shaped semi-conical ribs have been explored. The spiral-shaped semi-conical ribs have been designed with the aim of reducing the pressure drop across the rib so that thermal performance may be improved with a little increase in pressure drop after integrating the ribs into the SAH mainstream flow. The higher value of thermal-hydraulic performance indicates an increased heat transfer rate with a minimum increase in pumping power. In order to achieve the highest possible thermal enhancement factor, this experimental study intends to analyze the effects of different geometrical parameters on the heat transmission and friction behavior of numerous spiral-shaped semi-conical ribs. Multiple experiments were conducted using different levels of roughness heights to optimize the rib profile parameters. The Reynolds number (Re) ranges from 3358.65 to 18,095.59, the relative roughness height (e/Dh) 0.09 to 0.227, and relative roughness pitch (P/e) 3.7 to 5.5. These multiple spiral-shaped semi-conical ribs give the maximum thermal enhancement factor of 2.85 at (e/Dh) 0.182 and P/e of 4.1 at Reynolds number 18,095.59. It has been found that current rib geometry can increase the thermal performance of solar air heaters with minimum increased pumping power with reference to rib explored by earlier researchers.

A Review on Optimization of Thermal Performance of Solar Air Heater with artificial Surface Roughness

The requirement of energy across the globe is increasing at a distressing rate. The conventional sources of energy may no longer be able to meet the requisite demands. India being the second most populous country in the world having 20% of the total world population has a per capita energy consumption of 400 KWh. Hence, the need of hour is to hunt for the sources of energy which can lost longer and wouldn`t harm any forms of lives on the planet earth. Solar energy originating from sun is evolved by a series of chemical reactions that convert about 65*107 tons of Hy drogen to Helium every second. The energy from sun at a distance of 1.5*108 Km reaches the surfaces of collector plates installed on buildings and structures in beam and diffused forms of electromagnetic radiations. The former is called as direct radiation since they don`t change direction while travelling while as latter are subjected to scattering, absorption, re-radiations and re- reflections in the atmosphere.

Influence of triangular spoilers on the performance of serpentine solar air heaters

In order to improve the efficiency of the conventional serpentine solar air heaters, this article proposed a serpentine solar air heater containing a triangular spoiler. A 3-D verified mathematical model of serpentine solar air heaters with triangular spoilers was established. The results showed that the arranging triangular spoiler had a positive effect on enhancing the thermal performance of solar air heaters. It could be seen from the velocity and temperature contours that the triangular spoiler could reduce the intensity and area of the vortex zones, and hence decrease the temperature dead zone in the flow channel. The collection efficiency reached its peak value when the angle of triangular spoiler was 64°. Compared with the nontriangular spoiler, the collection efficiency was increased by 4.4% ∼6.2%. In general, the optimal angle of triangular spoiler was determined to be 40° by comprehensive analysis of effective efficiency.

Research on thermal performance and pressure loss of a new perforated-folded baffle solar air collector

In order to further improve the heat collection performance of solar air heaters and reduce internal pressure. This study establishes a collector with perforated baffle based on baffled collector. The model was simulated using CFD software. Fit and analyze the efficiency of the collector with the hole-opened rate (the ratio of the opening area to the baffle area). The results show that compared with non-perforated baffle collectors, perforated baffle collectors have lower pressure loss, higher collection efficiency, lower heat dissipation coefficient of about 37.58%, and higher heat transfer coefficient of about 10.51%. When the hole height is 30 mm, the hole diameter is 80 mm, and the hole-opened rate is 0.24, the coupling between heat collection efficiency and pressure loss is the best, which is 64.11% and 4.32 Pa, respectively. The heat collection efficiency decreases with the increase of porosity, and the fitting degree R 2 = 0.98. The deviation of fitting curve (between turbulence intensity and hole-opened rate) is less than 10%. Nusselt number increases gradually with the increase of Reynolds number. Fitting correlation between Nusselt number and Reynolds number, and fitting degree is 0.9985. Perforated-folded baffle collector provides theoretical basis for improving the solar thermal utilization rate.