Performance Of Solar Air Heater Research Articles

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.

Effect of jet-impingement and surface roughness on performance of solar air heater: Experimental study and its optimization

The performance of solar air heaters can be improved by either active or passive techniques. In this research manuscript, both active and passive technique is used to enhance the thermal characteristics of the solar air heater. The proposed solar air heater consists of an innovative approach in which an impinging air stream and wired ribs (arranged in the multiple V-pattern over the absorber plate) are used for performance improvement. The impinging air stream is synchronized in such a way that it strikes the ribs to promote local turbulence. The investigation has been performed considering various design parameters like relative width ratio, relative roughness height/pitch, the angle of attack, the stream-wise jet pitch, the span-wise jet-wise pitch, and the jet diameter ratio. The results have shown that the presence of the ribs opposite to the impinging air stream promotes local turbulence over the ribbed surface which ultimately enhances the thermal characteristics of the solar air heater. The proposed design is also been optimized using the surface response methodology and the significance of the various roughness parameters on the thermal characteristics has also been predicted. Additionally, the best performance observed is 3.12 at a relative width ratio of 5, relative roughness height/pitch of 0.043/10, angle of attack of 60˚, stream-wise jet pitch of 0.4, span-wise jet-wise pitch of 0.84, and jet diameter ratio of 0.064.

Energy storage concentrates on solar air heaters with artificial S-shaped irregularity on the absorber plate

This study utilizes the friction factor as a means to evaluate the impact of the roughness parameter on both heat transfer and pressure drop. This work involves doing an experimental and numerical investigation on the utilization of artificial roughness in solar air heaters situated in outdoor settings. The study examines the effects of using a rectangular S-shaped arrangement of artificial roughness, both in an inline and staggered configuration. The objective of this study is to validate the enhanced thermo-hydraulic performance of solar air heaters using various arrangements of artificial roughness shapes. The parameters considered include the length of the relative roughness (d/H = 1.33), the height of the relative roughness (e/H = 0.271), and the constant distance between S (b/H = 0.667). The Reynolds number is varied within the range of 3000 to 10,000, while the pitch range (p/H) is set to (1.667, 3.33, 5, 6.667) for in-line arrangements and (l/H) is set to (0.8335, 1.666, 2.5, and 3.335) for staggered arrangements. The results show that enhancing heat transfer using an artificial roughness staggered arrangement is the best. The maximum Nusselt number was observed at a dimensionless pitch-to-height ratio of 3.33 for both inline and staggered arrangements, with values of 4.87 and 4.2 times higher than that of the smooth duct, respectively.

A case study on thermal performance of solar air heater with down apex position of open trapezoidal ribs with gaps

This study aims to experimentally explore the impact of multiple open trapezoidal ribs with gaps (MOTRG) on the thermal efficiency of a rectangular duct in a solar air heater (SAH). The designed parameters of ribs i.e. relative limb length (L/w), relative pitch ratio (p/e), relative gap ratio (g/e) and relative rib height (e/Dh) are varied as 0.2–1.0, 6–12, 1–5 and 0.023–0.056, respectively. The experiments have been conducted for Reynolds number (Re) span of 2000–16000. Since then, open trapezoidal rib designs have made significant improvements to SAH performance. A highest value of 78.86% of thermal efficiency has been observed corresponding to α = 60°, g/e = 1, L/w = 0.8, p/e = 10, W/w = 6, and e/Dh = 0.043. The global best values of enhancement factors of 3.032, 2.726 and 2.496 have been found for insolation values of 1000 W/m2, 800 W/m2 and 600 W/m2. The findings demonstrate that, when compared to other roughened SAH ducts, the MOTRG roughened duct provides superior thermal performance.

Effect of jet angle and jet pitch on the Thermo-Hydraulic performance of solar air heater having absorber plate with jet impingement

This numerical investigation focuses on enhancing the heat transfer characteristics and thermo-hydraulic performance of a solar air heater by employing jet impingement over the absorber plate. The study explores the influence of two geometrical parameters, namely jet pitch ratio (P/Dh) and jet angle ratio (α/90), on the heat transfer, frictional losses, and overall performance of the solar air heater with jet impingement (SAHJI) under various flow conditions, represented by Reynolds numbers (Re) ranging from 3500 to 17500. The simulations are conducted using the RNG k-ɛ model with second-order upwind discretization. A comparative analysis is performed between the SAHJI system and a conventional smooth solar air heater (SPSAH) configuration, revealing a significant enhancement in thermal–hydraulic performance with the use of jet impingement. The investigation identifies the maximum thermo-hydraulic performance parameter, reaching a value of 4.12. This peak performance is achieved at specific values of jet pitch ratio (P/Dh) of 1.30 and jet angle ratio (α/90) of 0.094, respectively, at a Reynolds number of 7500. These findings demonstrate the potential of jet impingement as a heat transfer enhancement technique in solar air heaters, contributing to improved overall system efficiency.

Comprehensive review of key parameters for improving the performance of Solar Air Heaters

Due to declining supplies of once-affordable fossil fuels, research into renewable energy sources is being prioritized. Using solar energy for passive cooling and heating can significantly reduce the demand for primary energy sources. In this survey, we look at how changing a few variables might affect how well a solar air heater functions. It helps researchers learn more about these systems’ development, properties, and potential uses. This research analyses the current literature to emphasize the value of thermal properties. Focusing on laminar sublayer creation and increasing the heat transfer coefficient, it explores ways to increase the efficiency of solar air heaters. After reviewing several articles, it has been determined that rib roughness elements and their geometric characteristics play a significant role in enhancing the thermal performance of solar air heaters. The relative roughness height, pitch, angle of attack, and width are all important factors to consider.