Revisiting the Effect of Rib Roughness on the Performance of Solar Air Heater

. The energy collected from various renewable resources, such as sunlight, geothermal warmth, wind, and water, is referred to as renewable power. The sun is the ultimate source of vitality. Solar radiation vitality can be utilized in many functions, such as heating buildings and dusty foliage crops, dying chicken, wood taste, and treating modern elements. All the energy patterns in nature asking them are the origin of the sun. The solar air heater (SAH) is very common along with commonly applied sun-oriented heating apparatus. Perhaps, SAH is utilized for a wide range of applications, from residential to commercial. Improving the SAH efficiency is done by applying rib elements on the bottom side of the roughness element ribs, grooves, fins, baffles, twisted tapes, deflectors, etc., and improved Thermo-hydraulic performance (THP). Various investigators have prepared several practices in their research work to obtain a greater transfer of thermal energy between these solar collector heaters by applying various rib elements to the absorbent surface. The objective of that study is obliged to describe and conclude tests on the impact of modest rib element height and face projection upon absorber plate along duct surface as artificial rib elements of different shapes on heat transfer along friction factor. The research on artificially roughened SAH ducting is thoroughly analyzed in this paper. The purpose of this paper is to summarize several studies on the thermal and hydraulic performance of synthetically roughened SAH ducting. For the analyzed range of parameters, it was discovered that the usage of arc-shaped-shaped rib geometry and metal grit ribs has the maximum THP parameters in comparison to often roughness geometry. For the tested range of parameters, the use of broken arc ribs has the highest Nu compared to the plain arc-shaped rib roughness. Arc configuration of roughness element exhibits fewer ranges pressure diminishes than the V form design because the produced secondary flow has a curved structure and is rougher.


Introduction
Conventional energy sources have a limited supply of available resources.Therefore, more attention has to be paid to maximizing and applying renewable energy assets.The sun is the most powerful energy source.Such a gadget is a SAH, which transforms sun energy into heat energy.Figure 2 and presented types of flat plat solar collector and flat plate SAH respectively.SAHs have various applications, including building heating, crop and fruit drying, chicken brooding, timber seasoning, and industrial product curing.It's worth noting that all energy on Earth has a solar origin.Solar energy has distinct advantages over other forms of energy due to its cleanliness and its ability to provide energy without any negative environmental impact [1].Conventional SAHs can heat air more effectively by adding roughness to the underside of the absorber plate in many ways.The effectiveness of a SAH can be enhanced by a passive transfer of heat technique called artificial ribs.Incoming solar radiation is absorbed by SAH and converted into heat energy on the surface of the absorber plate.When air flows over an absorber plate, laminar and turbulent layers are formed over the plate's surface.Within these layers, close to the plate's surface, a laminar sub-layer is formed due to the presence of the observer, which slows down heat transfer to the flowing air and affects the thermal performance of the SAH.Artificially roughened absorber plates are the most suited solution to achieve a better heat transfer coefficient and solve this issue.As a result, the heat transfer coefficient was artificially increased to break up the laminar sub-layer and lower thermal resistance.In order to minimize friction loss, it is therefore preferable to induce a disturbance in the area immediately next to the surface of heat transfer, i.e., in the sub-layer of laminar alone [2].
Figure 1.Flat plate solar collector [3] , 01 (2023) E3S Web of Conferences ICMPC 2023 https://doi.org/10.1051/e3sconf/202343001264264 430 Figure 2. Flat plate SAH [2] Artificial roughened SAHs are usually subjected to a lot of experimentation and timeconsuming development.Due to the advent of computational fluid dynamics the design and optimization of these air heaters has been greatly simplified.The computational method is an efficient method of tackling the complicated problem of designing and optimizing of roughened SAHs that involves a wide range of complex and wide-ranging parameters.This technology has seen a significant uptick in adoption rates over the past few years in the design and optimization of SAHs.The results of these simulations show that the use of this tool is very effective in predicting the performance and behaviours of the air heater.In-depth evaluations on the SAH were presented in excellent review papers that took an experimental approach [4][5][6][7].The performance of SAH have been thoroughly analysed in a number of excellent review studies that take a computational approach [8][9][10][11].

Artificial roughness fundamentals
A passive heat transfer augmentation technology called artificial roughness can improve the THP of a SAH.Artificial roughness has substantially improved forced convective heat transfer, which also requires turbulent flow at the heat-transferring surface.However, the energy to create such turbulence must come from the fan or blower, and a tremendous amount of power is required to drive air through the duct.It is preferred for the turbulence to only arise in the region that is extremely close to the heat-transfer surface in order to minimize power consumption.By keeping a low roughness element height with the duct size, this can be accomplished.It has been shown that a more W/H rectangular channel that is symmetrically heated and is designed after SAH Channel considerably enhances the heat transfer coefficient along least amount for pressure loss penalty by adding rib elements to the surface of heat transfer [12].
This review paper's goal is to provide an overview of the work done to improve SAH performance by using artificial roughness/turbulators in a variety of configurations.To determine the ideal rib configuration, a laboratory inspection of different rib element geometry is also provided.The viewers of that inspection who are involved in improving heat transfer will find it useful.The idea of artificial roughness and its accompanying effect is covered in the subsection that follows.Also covered in detail is the performance of SAH with simulated roughness.Lau, McMillin and Han [13] examined the produced flow of air on a square duct along discrete turbulators in view of heat transfer coefficient (h) and friction factor (f).The e/Dh and p/e were both 0.0625 and 10, respectively.Re is 10,000 -80,000.The outcomes reflected that mean Stanton number (St) in 90o unique rib instances was around 10-15% more compared to 90o roughness element of transverse form cases. Zhang, Gu and Han [14] investigated the effect of compound turbulators on SAH.The rib-groove roughened wall incurred a 6 times greater pressure drop penalty and increased heat transmission by 3.4 times, compared to the rib-roughened wall, which had similar rib height and rib spacing and increased heat transfer by 2.4 times.Karwa [15] investigated the effect of different shape ribs in SAH.Due to an increase in the Nu, this study demonstrated a significant improvement in ηth10-40% = over SAH with plain absorber panels (50-120 percent).Absorber face of SAH's channel, Bopche and Tandale [16] tested h and f of specially designed inverted U-shaped turbulators.Re of 3800-18000, e/Dh between 0.0186 and 0.03986, and p/e between 6.67 and 57.14 were covered by the trials.Throughout the entire trial, the flow on turbulators was targeted at an angle of 90o.In comparison to the plain channel, the turbulator-roughened duct increases Nu and f by 2.82 and 3.72 times, respectively.Correlations between the averaged Nu and f for the turbulator-roughened duct were obtained.When using the parameters W/H of 8, e/Dh of 0.0168-0.0338,p/e of 10, Re of 3000-15000, and α of 30-75o, Kumar, Bhagoria and Sarviya [17] evaluated THP of SAH along discrete W form ribs on the absorber face plate.Additionally, correlations for the Nu and f were computed using the range of values selected.They found that for e/Dh=0.0338and α=60o, the friction factor is 2.75 and the increase in Nu is 2.16 in contrast to a plain SAH.In a test, Lanjewar, Bhagoria and Sarviya [18] looked at Nu along friction properties of a rectangular channel single broad fence that was roughened on the bottom by W-shaped ribs that were positioned perpendicular to the flow direction.The range of variables used was W/H of 8, p/e of 10, e/Dh of 0.018-0.03375,Re of 14000, and α of 30-75o.The greatest enhancement of Nu and f over a smooth channel for an α of 60o was found to be 2.36 and 2.01, respectively.Based on a turbulent flow via a SAH roughened duct, Yadav and Bhagoria [19] used CFD to model and simulate turbulent flows across SAH along square-cut form transverse roughness elements.Three different p and e values have been taken into consideration, with p/e = 14.29 being one of them.Re, varies between 3800 and 18,000.There is a range of 0.021 to 0.06 in e/Dh.According to the CFD predictions, e/Dh has a significant impact on the average Nu, average f, and THPP.For the range of parameters examined, a maximum value of the THPP of 1.8 has been discovered.Yadav and Bhagoria [20] conducted an evaluation of the application of CFD in the development of SAH.Outcomes of computations seem to show that for 2-D flow via conventional SAH, the RNG model yields the best results.Yadav and Bhagoria [21] explored 2-D incompressible Navier-Stokes flow through the purposefully roughened SAH pertinent Re ranges between 3800 and 18,000 in numerical research.Twelve unique equilateral triangular sectioned rib configurations (p/e of 7.14-35.71and e/Dh of 0.021-0.042)have been employed as roughness elements.A numerical technique based on finite volumes is used.ANSYS FLUENT simulates the turbulent airflow through a synthetically roughened SAH.A SAH that has been purpose fully roughened is evaluated to determine the appropriate roughness element design.Lanjewar, Bhagoria and Agrawal [22] designed evolution for many rib geometries used to create artificial roughness.There are offered the connections between f and Nu discovered by different academics.It is proven that the performance evaluation for various double arc rib roughness orientations.Gawande, Dhoble, Zodpe and Chamoli [23] to simulate 20o angled ribs and analyse mathematical modelling and simulation methods for thermal performance optimization, a MATLAB approach was employed.Gawande, Dhoble, Zodpe and Chamoli [24] performed experimental and CFD studies using reverse L-shaped ribs with Re of 3800-18000, e/Dh of 0.042, p/e of 7.14-17.86,and heat flow of 1000W/m2 have been used to evaluate the THP of a SAH.Using the RNG k-e turbulence model and the CFD code, ANSYS FLUENT, a 2D CFD simulation is carried out.

Enhancement of heat transfer through artificial rib elements in SAH
SAHs often use artificially rough surfaces to boost the heat transfer up to the laminar sub-layer.Adding ribs to the heated surface can further boost heat transfer by disturbing the viscous sub-layer and generating flow turbulence, separation, and reattachment, which can result in a higher heat transfer coefficient.The ribs are located exclusively on the heated wall, while the remaining all walls are flat and insulated.This setup is frequently observed in SAHs that feature absorber plates with artificial roughness.[25].

Performance analysis of SAH
In order to develop an effective system of this kind, it is necessary to conduct study on the thermal and hydraulic performance of a SAH: Thermal performance: Using the Hottel-Whillier-Bliss equation, it is possible to compute the thermal performance of a SAH reported by Rate of valuable energy gain is given by 1.3.3.Thermo-hydraulic Performance: Thermo-hydraulic performance (THP) can be calculated as follows The design of a solar collector should be desirable and take into account both the THP features of SAH in view to incremented energy of heat and transfer to the flowing fluid with the least amount of fan energy consumption [26,27].

Factors affecting the flow patterns of rib geometry
Roughness can be characterized by the following key dimensionless geometrical parameters: 1.4.1 Rib Height (e): It produces the following influence on the roughness element: a.If e < δ There will be no roughness influence.b.If e > δ There will be more roughness influence upon f as a contrast to Nu. c.If e >δ There will be an enhancement in Nu and moderate f could be dealt.

Channel aspect ratio (W/H):
That component is also highly important for finding THP.Table 1 shows the range of W/H for the enhanced rate of heat transfer:  2 displays the e/Dh value for maximal heat transfer rate.

Arc Angle (α).
Through relation to the direction of air movement in the duct, this is how inclined the ribs are.By angling the rib with regard to the flow, counter-rotating secondary flow is generated along the length, which changes the h length-wise.Table 2 displayed α for the highest rate of heat transfer.
1.4.7 The shape of the roughness element.Ribs might be transverse or inclined, continuous or broken, with or without gaps, V-shaped, or they can be three-dimensional isolated elements.Additionally, the roughness elements may have intricate rib grooves, dimples, or wired arcs.The most common shape for ribs is square, although THP has also been studied with circular, semi-circular, and chamfered designs.

Transverse continuous rib
With a tiny diameter protrusion wire on the absorber plate, Prasad and Saini [44] experimentally examined the friction factor and heat transfer coefficient of the fully developed turbulent flow in a SAH duct.The kind and direction of the geometry are presented in Figure 3.The comparison revealed that the friction factor mean deviation was 6.3 percent and Nu mean deviation was 10.7 percent.The greatest improvements in heat transfer coefficient and friction factor exceeded those of a smooth duct by 2.38 and 4.25 times, respectively.

Roughness element in transverse broken form
By placing 90o discrete transverse roughness upon an absorber plate, Sahu and Bhagoria [29] reported the impact of SAH on h and ƞth.Presented in Figure 4.With p ranges between 10 and 30 mm, e is 1.5 mm, W/H is 8, and Re is 3000-12000, the roughness geometry.Additionally, it was said that the maximum ƞth and h values achieved were 1.23 to 1.42 more than and 83.5 % higher than those of a plain channel, respectively.

Transverse inclined ribs
According to Kumar, Mittal, Thakur and Kumar [59], the experimental inspection was conducted to improve the h of a SAH that has an air duct that has been artificially roughened with 60o discrete inclined ribs.With such a roughness element, h has been significantly improved.Figure 5 depicts the geometry that was under investigation.In SAH shown in Figure 6, Aharwal, Gandhi and Saini [32] explored the impact of ribs by arranging inclined separated ribs in a rectangular channel.Consider the difference between the position ratio (d/w) and the relative gap width g/e.When compared to a plain channel, increases in Nu and f were 1.48 to 2.59 more than and 2.26 to 2.9 more than, respectively.

Roughness element in expanded wire mesh fixation
By placing an extended metal mesh shape upon the absorber face of a SAH, as depicted in Figure 7, Saini and Saini and Saini [60] experimentally evaluated the impact on the h and f.The maximum Nu and f for fully generated zig-zag flow between rectangular channels along a high W/H = 11.1 were noticed to be 46.87,71.87, and 25, 15 respectively.These values correspond to the relative L/e and S/e.The smooth absorber plate recorded the highest increase in Nu and f values of about 4 and 5 times, respectively.

Wedge roughness element
In a SAH rectangular channel that was roughened with a wedge form transverse integral roughness element and shown in Figure 10, Bhagoria, Saini and Solanki [48] conducted an experimental investigation to determine influences for different parameters.Wedge angle (ϕ) ranged from 8 to 15o, p/e ranged from 60.17 to 12.12, e/Dh ranged from 0.015 to 0.033, and Re ranged from 3000 to 18000.It has been shown that a p/e of roughly 7.57 results in the most heat transmission.Pitch increased as relative roughness dropped and f increased.At a wedge angle of roughly 10o, heat transmission is enhanced most.According to the author, compared to a smooth duct, the Nu increased by 2.4 and 5.3 more, respectively.

Regular W-ribs
Experimental research has been demonstrated by Lanjewar, Bhagoria and Sarviya [34] using the theory of a growing number of secondary cells in a w-shaped rib.The parameter's range was 0.018-0.03375for e/Dh, 10 for p/e, and 30-75o for α.The highest enhancement of Nu along f was 2.36 along 2.01, respectively was found at α of 60o.

W roughness element in discrete form
In order to investigate the h expansion in a SAH with that absorber panel non-smooth along separated w from roughness, Kumar, Bhagoria and Sarviya [61] performed a laboratory investigation.e = 0.75 mm-1 mm, e/Dh = 0.016-0.0224,p/e = 10, Re = 3000-15,000, and α of 45 o were all included in the experiment.Beneath equal flow criterion, THP of nonsmooth and smooth SAH were compared, and it was found that the roughened channel had THP that has been 1.2 to1.7 times greater for the range of criteria examined.Figure 12 illustrates the geometry that was examined.

Roughness element in an arc pattern
Saini and Saini [31] used an arc-shaped parallel wire shown in Figure 16, upon the absorber panel of a SAH to explore the influence of e/Dh and α/90 on h and f.With Re =2000-17000, e/Dh of 0.021-0.0422,and α/90 = 0.33-0.67 for a constant p/e = 10, the following specifications are used: The largest Nu enhancement was 3.80 times, which corresponds to an α/90 of 0.3333 at an e/Dh of 0.0422.However, it was discovered that the increase in f for these settings was just 1.75 times.

Discrete type
Muluwork, Saini and Solanki [64] compared the THP of staggered separated v-apex up and v-down roughness element along equivalent separated roughness disproved the validity of V-shaped ribs.The researchers discovered that the Stanton number was greater for V-down discrete ribs than for the corresponding V-up and transverse discrete ribs.According to parameters research indicated in Figure 24, the St reported enhancement was 1.32-2.47.

Roughness in multiple continuous forms
Using the theory of a rising number of secondary flow units, Hans, Saini and Saini [51] examined multiple continuous V-ribs.e/Dh of 0.019 to 0.043, p/e of 6 to 12, α of 30 to 75o, and W/w of 1 to 10, all of which were factors in the experiment.While f reached its maximum value for W/w of 10, the highest heat transmission occurred for W/w of 6.Both Nu along f , 01 (2023) E3S Web of Conferences ICMPC 2023 https://doi.org/10.1051/e3sconf/202343001264264 430 are 6.5 and 5.5 times higher than that eater plain duct of the parameter under investigation, respectively.Figure 28 depicts the geometry of roughness.

Roughness in multiple forms with the gap
By creating a gap, Kumar, Saini and Saini [36] made use of the concepts of turbulence and flow acceleration.Re = 2000 -20,000, relative width ratio was 6, Gd/Lv was 0.24 -0.8, g/e was 0.5 to 1.5, and α was 60o.According to their findings, the highest improvement in Nu and f was 6.3 and 6.1more than that of a plain channel, respectively depicted in Figure 29.In a laboratory inspection by Maithani and Saini [42], v-ribs along uniform margins were employed as turbulence promoters to increase the h.e/Dh = 0.044, p/e = 6-12, α = 30-75o, g/e =1-5, and Ng = 1-5 were all factors that were examined.The f enhanced through 3.67 times higher than the plain duct, reaching a maximum enhancement of 3.6 more than that of the plain channel.According to Figure 30.discrete double arc reverse curved roughness elements.He discovered that the smooth plate had maximum values of h and ƞth of 2.8 and 1.3, respectively.Additionally, experimental research has shown that Nu along f is 2.87 and 2.47 times stronger than on a smooth plate.Gawande, Dhoble, Zodpe and Fale [78] also used combined ribs.Table 3, lists the max value of Nu.

Conclusion
This research attempts to present the h and f characteristics of a SAH artificially roughened duct utilizing various rib geometries.The given conclusion is reached in light of the literature review: 1. Roughness elements used in SAH are a useful way to enhance heat movement to fluid moving across channel and it reported maximum transfer of heat compared to the plain surface under the uniform variable criterion.It has been determined that the various roughness geometry types employed in SAH depend on the configurations and positions of the ribs upon the absorber panel.2. When the surface of a SAH is roughened, the-rest noticeable enhancement in h along with an increase in flow friction.However, for each sort of rib geometry used, several researchers find a different number of increments in Nusselt number and friction factor.3.There are many different types of parameters that identify roughness elements, but the repetitive roughness element geometry for SAH is best defined by the dimensionless parameter.Specifically, aspect ratio (W/H), relative roughness pitch (p/e), relative roughness height (e/Dh), and angle of arc (α).Less W/H ranges provide higher THP in SAH along ducting whereas high W/H values have better ƞth. 4. Different industries use SAH in different ways.A certain form of geometry can be chosen depending on the energy needed.In this regard, the reviews in this paper may be helpful.By using artificial roughness, it can be recognized that more friction factor (f) results in higher pumping power needs.It is ideal for the SAH to be designed to transfer the most heat energy to the moving fluid while using the amount of blower energy possible.5.The numerous correlations created for Nusselt number and friction factor depends on the system operating parameters and researchers in their efforts to determine the values of the options.6.For the analyzed range of parameters, it was discovered that the usage of arc-shapedshaped rib geometry and metal grit ribs has the maximum THP parameters in comparison to often roughness geometry.For the tested range of parameters, the use of broken arc ribs has the highest Nu compared to the plain arc-shaped rib roughness.7. The use of a V-type baffle presented a well-known highest total THP that appeared at an analogous baffle thickness compared to arc-shaped with different configurations and v-type discrete shaped.8.The THP over the continuous ribs has significantly improved since gaps were made in them.The increase in pumping force is required because of the improvement in Nusselt number (Nu) caused by the gaps formed upon the gap from roughness elements against 1.0 to 1.4 assets.9.The highest THPP values are observed for an S pattern roughness, several V patterns, and arc pattern roughness in separated forms.10.Arc configuration of roughness element exhibits fewer ranges pressure diminishes than the V form design because the produced secondary flow has a curved structure and is rougher.
Finally, this article discusses the concept of artificial roughness used in the design of SAHs.It will provide useful information for researchers to carry out the necessary studies to find out the optimal design of the system.This article, according to the authors, will have given researchers a better understanding of artificial roughness.

5 ) 1 . 3 . 2 .
) Nusselt number (Nu) can be measured by Nu = ℎl/k (4) In addition, the following equation can be used to express the thermal efficiency of a SAH η tℎ = q u I = F R [ (τα) e − U L (T i − T a )/I ] (Hydraulic performance: According to the following equation, the pressure drop can be calculated as follows ΔP /doi.org/10.1051/e3sconf/202343001264264 430

Figure 4
Figure 4 Transverse broken ribs [29]In an experimental study, Varun, Saini and Singal[33]  discovered that the SAH had thermal perforation with a roughness element combined type inclined and transverse roughness element, along Re =2000-14000, p/e = 3-8, and e/Dh = 0.030.The value for p/e at 8 was found to produce the best thermal performance.

Figure 5
Figure 5 Transverse inclined continuous rib [59] An equilateral triangle SAH ducts Nu and f properties were examined experimentally by Bharadwaj, Kaushal and Goel [38] employing roughness element uniform in inclined shaped upon absorber face.Re of 5600 -28000, e/Dh of 0.021 -0.043, p/e of 8 -16, W/H of 1.15, and α =30-60o were the values employed.At a p/e of 12, the Nu reached its greatest value, on the other side at a p/e = 8, f reached its highest value.The THP metric reached its greatest value with a p/e = 12 and an α = 60o.In SAH shown in Figure6, Aharwal, Gandhi and Saini [32] explored the impact of ribs by arranging inclined separated ribs in a rectangular channel.Consider the difference between the position ratio (d/w) and the relative gap width g/e.When compared to a plain channel, increases in Nu and f were 1.48 to 2.59 more than and 2.26 to 2.9 more than, respectively.

Figure 6
Figure 6 Transverse inclined ribs with gap [32]Experimental studies on pressure drop, ∆p, and heat transmission properties of an artificially roughened SAH channel with inclined wires were conducted by Gupta, Solanki and Saini[45].They found that the f peaked at a 70 o angle of attack, whereas the h peaked at a 60 o angle.

Figure 13
Figure 13 depicts the geometry of roughness.

Figure 23 V
Figure 23 V shaped ribs continuous type [47]

Figure 31 V
Figure 31 V Type Baffle [40] Kumar, Prajapati and Samir [43] performed experimental analysis of Nu and f and their correlations development for SAH duct that was S roughness element with W/H of 12, p/e = 4-16, e/Dh = 0.021-0.053,W/w = 1-4, and Re of 2400-20000.According to experiment findings, the highest enhancement of Nusselt number along friction factor have been discovered at W/w of 3, p/e of 8, e/Dh of 0.043, and α of 60o, as depicted in Figure 32.

Figure 32 S
Figure 32 S Type Rib [43] Sharma and Kalamkar [54] used computational and experimental techniques to evaluate the effects of different rib topologies on the functionality of this SAH.Along the span of pitch, two combined truncated and transverse roughness elements have been applied.The investigations were e/H of 0.1, e/Dh of 0.055, α of 90o, Re of 4000-16,000, and p/e of 10.The positioning of the ribs inside a roughened duct significantly influenced the performance of the SAH.Kumar, Kumar Goel [65] discovered triangular duct section.The highest THPP, 2.75, is found in a rectangular roughness pattern with forwarding chamfering.Prakash and Saini [55] investigated different roughness in combined forms to determine how it affected the THP of a SAH.The laboratory parameters included 15 to 30 p/e, 2000 to 20,000 Re, 14 g/e, 0.04 e/Dh, and α = 60o.The maximum THPP range has been 3.66 at p/e = 25.In an experiment, performance of the SAH in respect to the effect of arc roughness in separated forms was examined by Kumar, Goel, Singh, Saxena, Kashyap and Rai [66].The criterion of the study ranged from 0.3 to 0.9 in d/x, 1-3 in the number of gaps, and 0.5 to 1.5 in g/e.The THPP obtained its highest value of 3.85 by W/w of 1, d/x of 0.6, and Ng = 3.Using numerical and experimental techniques, Singh Patel and Lanjewar [56] examined the influences of innovative V form roughness upon the functionality of SAH.The range of the research parameter was p/e = 6 to 14, while other parameters, such as p'/p of 4, r/e of 4, g/e of 4, α of 60o, e/Dh of 0.043, and Ng of 3, had Re ranging from 4000 -14,500.The highest improvement occurred in Nu of 1.55-2.26and f of 2.63 -3.40 at p/e of 10 and 8, respectively, compared to a plain face.The maximum range of THPP of 1.59 has been reached at p/e of 10 and Re of 12,364.Correlations were also available for artificially roughened SAHs [39, 65, 67-73].Alam, Kumar and Balam [57] quantitatively inspected the impact of protrusion roughness in the conical form on THP about SAH.The study's parameters were e/Dh of 0.02 -0.044 and p/e of 6 -12.Protrusions roughnesses in conical form have a significant influence on how well SAH works.Agrawal and Bhagoria [58] explained practical inspection upon influences of a particular kind of ribs without a gap on the THP of the SAH used a doublereverse arc pattern.The experimental parameters used were p/e = 8.33 and = 30 o -75 o , followed by p/e = 6.67 to 11.67 and α = 60 o .The f was 0.0342 at e/Dh = 0.027, Re = 3010, and = 60 o .Tanda and Satta [74] examined the effectiveness of a rectangular duct in relation to the effects of intersecting and 45 o angled rib roughness.The flow was parallel to the ribs that connected them.The junction of the ribs boosted the duct's THP by increasing turbulence.Enhancement in Nusselt number (Nu) has been somewhat more when dual crossing roughness have been employed in place one of them crossing rib.The effects of a reverse roughness in double arc manner with uniform spacing upon SAH's performance were subject for experimental investigation by Agrawal, Bhagoria and Pagey [75].Ranges of changed criterions were 10, 30, and 3000 to 14000 for p/e and Re, respectively.The smooth surface showed the biggest increases in friction factor and Nusselt number, which have been 2.4 and 2.8 much more than respectively.Maximum ranges of THPP, 2.41, has been found when p/e of 10 along e/Dh of 0.0270.In the course of their outdoor experimental operation, Agrawal, Bhagoria and Pagey [76], [77] discussed how to improve thermal efficiency for /doi.org/10.1051/e3sconf/202343001264264 430 Yadav A S and Bhagoria J L 2015 Numerical investigation of flow through an artificially roughened solar air heater International Journal of Ambient Energy 36 87-100 81.Gawande V B, Dhoble A S, Zodpe D B and Chamoli S 2015 Experimental and CFDbased thermal performance prediction of solar air heater provided with right-angle triangular rib as artificial roughness Journal of the Brazilian 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95.Prasad R, Yadav A S, Singh N K and Johari D 2019 Advances in Fluid and Thermal Engineering, Lecture Notes in Mechanical Engineering, ed P Saha, et al. (Singapore: Springer) pp 613-26 96.Yadav A S, Shrivastava V, Chouksey V K, Sharma A, Sharma S K and Dwivedi M K 2021 Enhanced solar thermal air heater: A numerical investigation Materials Today: Proceedings 47 2777-83 97.Singh I and Singh S 2018 CFD analysis of solar air heater duct having square wave profiled transverse ribs as roughness elements Solar Energy 162 442-53

Table 1
Ranges of W/H for an enhanced rate of heat transfer.Relative roughness height (e/Dh).It is defined as the ratio of the roughness element height to the equivalent air passage diameter.Nu and f both rise as e/Dh does.Table

Table 2 :
Researchers, roughness pattern, Reynolds number and optimum performance parameter values of roughness elements.
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Lanjewar A M, Bhagoria J L and Agrawal M K 2015 Review of development of artificial roughness in solar air heater and performance evaluation of different orientations for double arc rib roughness Renewable and Sustainable Energy Reviews 43 1214-23 23.Gawande V B, Dhoble A S, Zodpe D B and Chamoli S 2016 Analytical approach for evaluation of thermo hydraulic performance of roughened solar air heater Case Studies in Thermal Engineering 8 19-31 24.Gawande V B, Dhoble A S, Zodpe D B and Chamoli S 2016 Experimental and CFD investigation of convection heat transfer in solar air heater with reverse L-shaped ribs Solar Energy 131 275-95 25.Joule J P 1861 VIII.On the surface-condensation of steam Philosophical transactions of the Royal Society of London 133-60 26.Prasad K and Mullick S C 1983 Heat transfer characteristics of a solar air heater used for drying purposes Applied Energy 13 83-93 27.Prasad B N 2013 Thermal performance of artificially roughened solar air heaters Solar Saini R P and Saini J S 2012 Experimental investigation on heat transfer and fluid flow characteristics of air flow in a rectangular duct with Multi v-shaped rib with gap roughness on the heated plate Solar Energy 86 1733-49 37. Yadav A S and Bhagoria J L 2013 A CFD (computational fluid dynamics) based heat transfer and fluid flow analysis of a solar air heater provided with circular transverse wire rib roughness on the absorber plate Energy 55 1127-42 38.Bharadwaj G, Kaushal M and Goel V 2013 Heat transfer and friction characteristics of an equilateral triangular solar air heater duct using inclined continuous ribs as roughness element on the absorber plate International Journal of Sustainable Energy 32 515-30 39.Singh A P, Varun and Siddhartha 2014 Heat transfer and friction factor correlations for multiple arc shape roughness elements on the absorber plate used in solar air heaters Experimental Thermal and Fluid Science 54 117-26 40.Kumar R, Kumar A, Chauhan R and Sethi M 2016 Heat transfer enhancement in solar air channel with broken multiple V-type baffle Case Studies in Thermal Engineering 8 187-97 41.Deo N S, Chander S and Saini J S 2016 Performance analysis of solar air heater duct roughened with multigap V-down ribs combined with staggered ribs Renewable Energy 91 484-500 42.Maithani R and Saini J S 2016 Heat transfer and friction factor correlations for a solar air heater duct roughened artificially with V-ribs with symmetrical gaps Experimental Thermal and Fluid Science 70 220-7 43.Kumar K, Prajapati D R and Samir S 2017 Heat transfer and friction factor correlations development for solar air heater duct artificially roughened with 'S' shape ribs Varun and Thakur N S 2012 Correlations for solar air heater duct with dimpled shape roughness elements on absorber plate Solar Energy 86 2852-61 53.Pandey N K, Bajpai V K and Varun 2016 Experimental investigation of heat transfer augmentation using multiple arcs with gap on absorber plate of solar air heater Solar Energy 134 314-26 54.Sharma S K and Kalamkar V R 2017 Experimental and numerical investigation of forced convective heat transfer in solar air heater with thin ribs Solar Energy 147 277-91 55.Prakash C and Saini R P 2019 Heat transfer and friction in rectangular solar air heater duct having spherical and inclined rib protrusions as roughness on absorber plate Experimental Heat Transfer 32 469-87 56.Singh Patel S and Lanjewar A 2019 Experimental and numerical investigation of solar air heater with novel V-rib geometry Journal of Energy Storage 21 750-64 57.Alam T, Kumar A and Balam N B 2020 Thermo-Hydraulic Performance of Solar Air Heater Duct Provided with Conical Protrusion Rib Roughnesses.In: Advances in Energy Research, Vol. 2, ed S Singh and V Ramadesigan (Singapore: Springer Singapore) pp 159-68 58.Agrawal Y and Bhagoria J L 2021 Experimental investigation for pitch and angle of arc effect of discrete artificial roughness on Nusselt number and fluid flow characteristics of a solar air heater Materials Today: Proceedings 46 5506-11 59.Kumar S T, Mittal V, Thakur N S and Kumar A 2011 Heat transfer and friction factor correlations for rectangular solar air heater duct having 60 inclined continuous discrete rib arrangement Br J Appl Sci Technol 3 67-93 60.Saini R P and Saini J S 1997 Heat transfer and friction factor correlations for artificially roughened ducts with expanded metal mesh as roughness element International Journal of Heat and Mass Transfer 40 973-86 61.Kumar A, Bhagoria J L and Sarviya R M Heat transfer enhancement in channel of solar air collector by using discrete w-shaped artificial roughened absorber.62. Bhushan B and Singh R 2011 Nusselt number and friction factor correlations for solar air heater duct having artificially roughened absorber plate Solar Energy 85 1109-18 63.Yadav S, Kaushal M, Varun and Siddhartha 2013 Nusselt number and friction factor correlations for solar air heater duct having protrusions as roughness elements on absorber plate Experimental Thermal and Fluid Science 44 34-41 64.Muluwork K B, Saini J S and Solanki S C 1998 Studies on discrete rib roughened solar Shrivastava V, Ravi Kiran T and Dwivedi M K 2021 Recent Advances in Mechanical Engineering, Lecture Notes in Mechanical Engineering, ed A Kumar, et al. (Singapore: Springer) pp 217-26 69.Yadav A S, Shrivastava V, Sharma A and Dwivedi M K 2021 Numerical simulation and CFD-based correlations for artificially roughened solar air heater Materials Today: Proceedings 47 2685-93 70.Kumar V 2019 Nusselt number and friction factor correlations of three sides concave dimple roughened solar air heater Renewable Energy 135 355-77 71.Yadav A S, Dwivedi M K, Sharma A and Chouksey V K 2022 CFD based heat transfer correlation for ribbed solar air heater Materials Today: Proceedings 62 1402-7 72.Kumar R, Chauhan R, Sethi M and Kumar A 2017 Experimental study and correlation development for Nusselt number and friction factor for discretized broken V-pattern baffle solar air channel Experimental Thermal and Fluid Science 81 56-75 73.Kumar A and Layek A 2019 Nusselt number and friction factor correlation of solar air heater having twisted-rib roughness on absorber plate Renewable Energy 130 687-99 74.Tanda G and Satta F 2021 Heat transfer and friction in a high aspect ratio rectangular channel with angled and intersecting ribs International Journal of Heat and Mass ://doi.org/10.1051/e3sconf/202343001264264 430 98. Yadav A S and Sharma S K 2021 Advances in Fluid and Thermal Engineering, Lecture Notes in Mechanical Engineering, ed B S Sikarwar, et al. 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