Extended Surfaces Research Articles

Simulation for charging of phase change material in existence of nanomaterial within solar energy storage system

Regarding possible solutions for thermal management of the storage unit, probably the main remedy might be to equip the system with an extended surface made from metallic materials which have high conductivity. In this study, by changing the number (n) and thickness (t1) of plates, four arrangements of the system have been suggested and solid matrix were made of three materials namely: Silicon Carbide (SiC), Aluminum (Al) and Stainless Steel (SS). Moreover, the heat absorption of phase change material (PCM) has been improved with loading of alumina nanoparticles. Increasing the number of radial plates and decreasing their thickness makes the heating penetration to increase. When the structure of geometry for SiC plates changes from (n = 5, t1 = 4 mm) to (n = 40, t1 = 0.5 mm), the melting time declines around 63.87 %. With changing the material from SS to SiC, the period of melting decreases about 66.33 % when n = 5, t1 = 4 mm. The worst case among scrutinized cases in view of speed of melting happens when n = 5, t1 = 4 mm involving Al. The best case occurs when n = 40, t1 = 0.5 mm involving SiC material and its melting time is 87.84 % lower than that of the worst case.

(Invited) Extended Thin Film Platinum Group Metal Electrocatalysts with Different Mesoscale Morphologies

The lack of sufficiently active oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts is a bottleneck to the proliferation of PEM fuel cells and water electrolyzers. Commercially available PGM electrocatalysts fail to attain DOE technical targets due to instabilities and activity losses incurred at low loadings. Morphology control of PGM nanostructures is an enticing route towards activity and stability enhancements of electrocatalysts, but not much is known about the structure-property relationships between PGM mesoscale geometry (5 to 100 nm) and their activity and stability.This talk presents our work on model Pt extended surface electrocatalysts of tunable feature sizes and morphologies prepared from self-assembled block copolymer templates. The morphology, either perpendicular lamellae, cylinders, or perforated cylinders, of the extended surface electrocatalyst was controlled by the block copolymer volume fraction. The periodic lateral feature sizes (10 to 40 nm in this work) were controlled by the block copolymer degree of polymerization. The self-assembled block copolymers were transformed into extended surfaces using sequential infiltration synthesis to prepare aluminum oxide followed by reactive ion etching to remove the block copolymer template. Pt was sputtered onto the aluminum oxide supports. ORR data in a RDE with the new extended nanostructured thin films of Pt showed mass activity values of 0.35 A mgPt-1 to 0.46 A mgPt -1 at 0.9 V vs. RHE. The measured electro-chemically active surface area (ECSA) values obtained from hydrogen underpotential deposition were 64 to 70 m2 gPt -1. The lower values hailed from lamellae morphology while the larger values corresponded to a cylindrical morphology. The measured mass activity values, which have no cobalt or nickel additives and are unoptimized and display competitive mass activity values for ORR. We envision that the block copolymer templated extended surfaces could be an alternative to 3M’s state-of-the-art nanostructured thin film technology.

Investigating heat transfer enhancement for PCM melting in a novel multi-tube heat exchanger with external fins

The low thermal conductivity coefficient is the limiting parameter of phase change materials (PCMs) for using in thermal energy storage systems. Various heat transfer enhancement methods such as utilizing extended surfaces techniques which include finned tubes and multi-tubes are studied. In this paper the melting of a PCM is investigated in a novel multi-tube heat exchanger (MTHX). RT35 and water are used in the outer and inner tube as the PCM and the heat transfer fluid (HTF), in turn. The main purpose of this study is to peruse the effect of installing external longitudinal fins on the inner tube (tubes) during the charging process. Two, three, and four tubes are engaged to check the effect of inner tubes number on the melting process with a constant amount of PCM and the HTF mass flow rate. A two-dimensional finite volume method based on the enthalpy–porosity technique has been developed using FLUENT software. A comparison between MTHX without fins and with external fins shows that adding of fins improves the heat transfer rate, more uniform temperature distribution, and reduced melting time. The PCM melting time was reduced by 27.84 %, 33.8 %, 29.84 %, and 29.55 % in cases A, B, C, and D, respectively, by installing external fins on the MTHX.

Greater transmission capacities and small-world characteristics of bacterial communities in the above- than those in the below- ground niches of a typical submerged macrophyte, Vallisneria natans

Leaves and roots of submerged macrophytes provide extended surfaces and stable internal tissues for distinct microorganisms to rest, but how these microorganisms interact with each other across different niches and ultimately drive the distribution through horizontal and vertical transmissions remains largely undetermined. Knowledge of the mechanisms of assemblage and transmission in aquatic macrophytes-associated microbial communities will help to better understanding their important roles in plant fitness and benefit ecological functions. Here, we conducted a microcosmic experiment based on in situ lake samples to investigate the bacterial community assemblage, transmission, and co-occurrence patterns in different niches of a typical submerged macrophyte, Vallisneria natans (V. natans), including seed endosphere, as well as environmental (water and bulk sediment), epiphytic (phyllosphere and rhizosphere), and endophytic (leaf and root endosphere) microhabitats of both leaves and roots representatives of the above- and below- ground niches (AGNs and BGNs), respectively. We found the bacterial communities colonized in epiphytic niches not only exhibited the highest diversity compared to adjacent environmental and endophytic niches, but also dominated the interactions between those bacterial members of neighboring niches in both AGNs and BGNs. The host plants promoted niche specificity at bacterial community-level, as confirmed by the proportion of bacterial specialists increased with plant proximity, especially in the BGNs. Furthermore, the bacterial taxa colonized in the AGNs exhibited higher horizontal and vertical transmission capacities than those in the BGNs, especially in the vertical transmission from seeds to leaves (41.38 %) than roots (0.42 %). Meanwhile, the bacterial co-occurrence network in AGNs was shown to have stronger small-world characteristics but weaker stability than those in the BGNs. Overall, this study cast new light on the plant microbiome in the aquatic environment, thus better promoting the potential development of strategies for breeding aquatic macrophyte holobiont with enhanced water purification and pollutant removal capabilities in the future.

Polypeptide N-acetylgalactosaminyltransferase (GalNAc-T) isozyme surface charge governs charge substrate preferences to modulate mucin type O-glycosylation.

A large family of polypeptide N-acetylgalactosaminyltransferases (GalNAc-Ts) initiate mucin type O-glycosylation transferring α-GalNAc from a UDP-GalNAc donor to the hydroxyl groups of Ser and Thr residues of peptides and proteins, thereby defining sites of O-glycosylation. Mutations and differential expression of several GalNAc-Ts are associated with many disease states including cancers. The mechanisms by which these isozymes choose their targets and their roles in disease are not fully understood. We previously showed that the GalNAc-Ts possess common and unique specificities for acceptor type, peptide sequence and prior neighboring, and/or remote substrate GalNAc glycosylation. In the present study, the role of flanking charged residues was investigated using a library of charged peptide substrates containing the central -YAVTPGP- acceptor sequence. Eleven human and one bird GalNAc-T were initially characterized revealing a range of preferences for net positive, net negative, or unique combinations of flanking N- and/or C-terminal charge, correlating to each isozyme's different electrostatic surface potential. It was further found that isoforms with high sequence identity (>70%) within a subfamily can possess vastly different charge specificities. Enzyme kinetics, activities obtained at elevated ionic strength, and molecular dynamics simulations confirm that the GalNAc-Ts differently recognize substrate charge outside the common +/-3 residue binding site. These electrostatic interactions impact how charged peptide substrates bind/orient on the transferase surface, thus modulating their activities. In summary, we show the GalNAc-Ts utilize more extended surfaces than initially thought for binding substrates based on electrostatic, and likely other hydrophobic/hydrophilic interactions, furthering our understanding of how these transferases select their target.

Bioconvective gyrotactic microorganisms in third-grade nanofluid flow over a Riga surface with stratification: An approach to entropy minimization

Abstract Interest in the thermal effects of nanofluid (NF) has increased recently due to the use of nanocomposites to magnify the thermal conductivity of conventional liquids and so boost the heat transit phenomena. Based on this fundamental concept, the current study inspects the thermal advanced third-grade fluid flow with nanocomposites with an extended surface and the inclusion of stratification, non-Fourier heat flux, mass flux, and radiation. Buongiorno’s NF model is employed to observe the thermophoresis and Brownian motion properties. The gyrotactic microorganisms, which are connected to the bioconvection phenomenon that intrigues most, are also considered to be present in the nanoparticles. The governing models are composed of partial differential equations; thereafter, the relevant transformations are applied to these equations to convert the structure into an ordinary differential model. These resultant models are solved by implementing the homotopy analysis method. It is explained in detail how the pertinent parameters are affecting the motion, temperature of fluid, nanocomposite volume, dynamic microbe density, skin friction rates, local Nusselt, and local Sherwood numbers. Applications for the flow of nanoparticles carrying gyrotactic microorganisms include enzyme biosensors, microfluidic devices, microbial fuel cells, and biotechnology.

Active cooling of high concentrator panels with multi-junction modules by confined liquid impingement over the extended surfaces

The use of an efficient and reliable method to cool multi-junction cells in a high concentrator photovoltaic/thermal system leads to higher net output power in addition to improving the service life of the cells. The present study numerically investigates the cooling effect of a liquid-confined submerged jet impinged over the extended heat transfer surfaces in the back of the solar cells. The method is considered for the four high concentrator photovoltaic/thermal system designs. All systems include panels with two symmetry lines and four symmetric multi-junction modules under a concentration ratio of 1000 suns and a laminar flow of coolant. Extended heat transfer surfaces were designed as arrangements of rectangular fins inside a heat sink. According to the results, the hybrid cooling designs exhibited better cooling performance than confined jet impingement cooling. The temperature of the solar cells in one of the proposed designs at an inlet mass flow rate of 200g/min was 58.7 °C, which was smaller than the corresponding temperature of 70.4 °C in a similar finless design. For the proposed design, the electrical efficiency of the cells improved from 38.16 % to 38.71 % at the same inlet mass flow rate. This cooling scheme also reduced the temperature non-uniformity across the cells to 3 °C in some of the proposed designs.

An Overview of the Nano-Enhanced Phase Change Materials for Energy Harvesting and Conversion.

This review offers a critical survey of the published studies concerning nano-enhanced phase change materials to be applied in energy harvesting and conversion. Also, the main thermophysical characteristics of nano-enhanced phase change materials are discussed in detail. In addition, we carried out an analysis of the thermophysical properties of these types of materials as well as of some specific characteristics like the phase change duration and the phase change temperature. Moreover, the fundamental improving techniques for the phase change materials for solar thermal applications are described in detail, including the use of nano-enhanced phase change materials, foam skeleton-reinforced phase change materials, phase change materials with extended surfaces, and the inclusion of high-thermal-conductivity nanoparticles in nano-enhanced phase change materials, among others. Those improvement techniques can increase the thermal conductivity of the systems by up to 100%. Furthermore, it is also reported that the exploration of phase change materials enhances the overall efficiency of solar thermal energy storage systems and photovoltaic-nano-enhanced phase change materials systems. Finally, the main limitations and guidelines for future research in the field of nano-enhanced phase change materials are summarized.

Evaluation of Heat Transfer Coefficient for Plane and Perforated with Circular Perforations

This study focuses on the analysis of extended surfaces, which are commonly employed in various engineering applications to enhance convection heat transfer. The objective is to effectively increase the heat transfer rate by introducing perforations into the lateral surface of the fins. By determining the optimal perforation design and shape for these fins, this research aids in selecting the most suitable configuration. In preparation for the examination, aluminum and copper fins are specifically selected because of their elevated thermal conductivities and extensive use in heat transfer applications. The choice is based on their respective thermal conductivities: aluminum has a thermal conductivity of 210W/mK, while copper boasts a higher thermal conductivity of 410W/mK. KEY WORDS: Heat Transfer (HT), Heat Transfer Coefficient (HTC), Fins, Temperature and Perforations.

Transient thermal management characteristics of a porous fin with radially outwards fluid flow

Thermal management and energy storage problems often utilize extended surfaces, also known as fins for enhanced heat transfer. While thermal conduction is usually the dominant mode of heat transfer in a solid fin, the use of porous fins that include advective thermal transport due to porous fluid flow has also been investigated. In particular, the steady state thermal performance of a porous fin with pressure-driven radially outwards flow has been studied. While such results are helpful for studying problems that are inherently steady state in nature, such results do not readily apply to problems where heat removal or energy storage occurs only over a short period of time. This work presents transient thermal analysis of a porous fin with radial porous fluid flow driven by a pressure gradient. It is shown that the transient temperature field in the fin is governed by a transient convection-diffusion-reaction (CDR) equation, the solution for which is derived in the form of Bessel functions. Based on this solution, the evolution of fin performance with time is examined. Comparison of heat removed by the porous fin with a baseline case without any fin is carried out. The time taken to reach steady state is calculated. Key non-dimensional parameters appearing in this problem are identified and their impact on fin performance over time is investigated. Since fin porosity improves advective thermal transport but suppresses diffusive transport at different rates at different times, therefore, it is shown that for a given operating time, there may exist an optimal porosity that maximizes the rate of heat removal. It is shown that the operating time period of the fin plays a key role in determining whether fin porosity strongly impacts heat removal rate or not. Consequently, it is shown that it is important to consider transient effects in determining whether the use of a porous fin is beneficial at all, and, if so, what is the optimal fin porosity to use. This work contributes towards porous fin theory, and offers practical design guidelines for improving and optimizing the transient performance of porous fins.

Myeloprotection with activated carbon in doxorubicin-treated rats

Chemotherapy can often cause a variety of side effects including bone marrow (BM) suppression, termed as myelosuppression. Accordingly, facile and effective management of chemotherapy-induced myelosuppression is currently a pivotal task for experimental pathologists and oncologists. Here, we chose to use activated carbon (AC) with an extensive surface area for studying its possible protective effectiveness with respect to BM in doxorubicin (DOX)-treated rats. Spherical AC with an extended surface area up to 4490 m2/g was prepared for per os (p/o) delivery, whereas for intraperitoneal (i/p) delivery we used the powdered form of AC that was derived from the aforementioned spherical AC. During the monthly treatment of animals with AC and DOX these two components were delivered alternately (not in the same day). After treatment, BM cells were isolated from femurs of sacrificed animals, stained with acridine orange (AO) and analyzed by flow cytometry. Regardless of the route of AC delivery (p/o or i/p), apparent myeloprotection with a possible regenerative effect was observed in animals that received DOX, as evidenced by recovery of the populations of total nucleated cells (TNC) and polychromatic (immature) erythrocytes accompanied by a considerable reduction of the number of apoptotic/dead cells among TNC (≤2.0%). Moreover, as a result of AC administrations, there was a significant increase of AO green and far-red fluorescence intensities in the population of TNC, which is suggestive of the ongoing quantitative and conformational changes in DNA and RNA associated with cell recovery and proliferation. Thus, AC preparations under the present experimental conditions can effectively tackle DOX-induced myelosuppression via mechanisms not necessarily associated with adsorptive detoxification.

Comparative study of hybrid nanofluid flows over a bidirectional stretched surface with the impact of Hall current and ion slip

Hybrid nanofluids generally exhibit better thermal efficiency than traditional nanofluids due to the synergistic effects of different types of nanoparticles. The combination of these nanoparticles can improve stability, thermal conductivity, and heat transfer performance. This study aims to investigate the effects of Hall current and ion slip on a three-dimensional, steady flow of hybrid nanofluid induced by a bidirectional extending surface while considering the presence of Zinc oxide (ZnO) and Gold (Au) nanoparticles dispersed in Kerosene oil and water to establish two different hybrid nanofluids. Additionally, a heat transfer analysis is conducted in the presence of Cattaneo-Christov (C-C) heat flux and variable heat source/sink. The characteristics of fluid flow are elaborated using the Tiwari and Das model, and a comparison between the two hybrid nanofluid models is presented in detail. The novelty of the envisioned model lies in the heat transfer comparison of two assumed hybrid nanofluid flows in the presence of Hall current and the ion slip over a bidirectional extended surface. The other assumed factors also boost the uniqueness of the model under consideration. To convert the flow model of partial differential equations into ordinary differential equations, relevant transformations are implemented, which are then numerically handled using the bvp4c scheme. The consequences of dimensionless quantities on flow and temperature distributions are highlighted using graphs, and the surface drag coefficients and surface heat transfer rates are also assessed and summarized. The study shows that ZnO-Au/water combination leads to higher heat transfer rates compared to ZnO-Au/Kerosene Oil. Additionally, the proposed model is validated in this research work.

Struvite Got by a Modified Technology as the Basis of an Environmentally Friendly Controlled-release MgNP-fertilizer

The results of a quantitative analysis of nutrients based on samples of struvite as a controlled release nitrogen-phosphorus fertilizer, obtained using two technology options, were presented. It was shown that the use of traditional struvite deposition technology leads to the formation of a coarse-grained product (average crystal size 578 μm). It was confirmed that the modified technology allows to obtain highly dispersed struvite (average crystal size 19 μm) with a more extended particle surface and an ammonium content of 98–99% of the theoretical value with a higher nutrient release rates compared to struvite got by conventional technology. Struvite synthesized by the modified technology was found to show improved performance as a controlled release MgNP fertilizer.

Bifurcated divergent microchannel heat sinks for enhanced micro-electronic cooling

The thermal performance of microchannel heat sinks (MHSs) can be enhanced by utilizing extended surfaces such as pin fins, ribs, and bifurcation plates. Extended surfaces, however, adversely affect the hydraulic performance of the MHSs. Divergent microchannels, on the other hand, offer higher hydraulic performances but lower thermal performances than parallel microchannels. Here, bifurcated divergent MHSs are studied to examine the opposing effects of bifurcation and divergence on the thermo-hydraulic performance. Bifurcation plates with constant cross-section, variable width, and variable height are considered. Results showed that the pressure drop penalty and average heat transfer coefficient of bifurcated divergent MHSs are lower than the parallel MHSs. Considering the performance index (PI) defined as the ratio of heat transfer coefficient to pressure drop penalty, the bifurcated divergent microchannels outperform the parallel MHSs. Results also revealed that increasing the width of the bifurcation plate in the flow direction decreases the overall performance of the bifurcated divergent microchannels. The divergent bifurcation microchannels with a variable height bifurcation plate outperform the ones with a constant cross-section bifurcation plate. This study confirms the advantage of bifurcated divergent microchannels for increasing the cooling performance of the MHSs.

Efficiency improvement of the solar chimneys by insertion of hanging metallic tubes in the collector: Experiment and computational fluid dynamics simulation

The solar chimney power plant (SCPP) is a straightforward and clean technique to generate electricity from solar radiation. However, this technology still faces major challenges, such as low efficiency, which has hindered its industrialization. This study experimentally develops a novel collector design to improve the solar chimney collector's efficiency. The new design includes metallic tubes as solar radiation absorbers hung from the canopy of the collector. The metallic tubes are open at the top and sealed with transparent sheets at the bottom to decrease the solar radiation reflected into the ambient air. Experimental and 3-D computational fluid dynamics (CFD) analyses are performed to validate the new design. The effects of hanging metallic tubes on temperature and velocity distribution are explored. The temperature increased by about 5 K at the chimney inlet, causing a roughly 8% rise in collector efficiency due to the fact that metallic tubes operate as an extended surface. The impact of various tube geometries on solar chimneys' efficiency is examined. The CFD findings reveal that the metallic tube geometry variation has considerably impacted the collector's efficiency. Thus, the collector efficiency is increased by changing tube diameter by around 33.7%, similar to changing tube length by 30%.

Computational fluid dynamics investigations over conventional and modified Savonius wind turbines

Wind turbines are devices that convert the kinetic energy present in the wind into clean, sustainable, and effectively renewable energy that could be used to generate electricity. A Savonius wind turbine is a drag-based vertical axis wind turbine (VAWT) that is known to have low noise levels and good starting characteristics even at low wind speeds. Its disadvantage lies in its low efficiency or low coefficient of performance. Exploring ways to increase the coefficient of performance, numerical investigations were carried out on different modified Savonius VAWT configurations, having different curvatures, different overlap percentages, added mini blades, and fitted out with extended surfaces. These investigations were computationally executed on Ansys Fluent™ using the sliding mesh technique. Two-dimensional simulations, on a Bach blade curvature with zero overlap as well as a half-circle and a polynomial curvature with overlap, showed that for a wind speed of 5 m/s and a tip speed ratio of 0.8, the half-circle blade curvature having an overlap of 20% performs best, yielding the highest net (average) coefficient of moment, equal to 0.3065. Results also show that the addition of mini blades to this optimal configuration produces a slight improvement in the coefficient of moment. However, the addition of extended surfaces onto the blades caused the minimum coefficient of moment to be a substantial negative value and thus resulting in a much lower value for the turbine's average coefficient of moment.

Chemically reactive magnetized tangent hyperbolic bidirectional nanofluid flow subject to interaction of gyrotactic moment of microorganisms and nanoparticles

The exploration of nanofluids have many applications in oils, microelectronics, compact heat exchangers, cooling of an infinite metallic plate, in power transportation, mineral water, plastic and rubber sheet manufacturing nuclear reactor design, electronics, solar energy, making it an identical influential scientific field. The inspiration of activation energy occurring within a chemical reaction has been extensively useful in manufacturing of oil reservation, biodiesel, geothermal accomplishment, oil, base liquid procedure, food manufacturing, oil amalgamate, sewage systems, along with a significant renewable energy source. We have studied the effect of MHD on steady 3D tangent hyperbolic nano fluidic flows through an extended surface containing gyrotactic microorganisms by considering new mass flux conditions in this research article. With the help of Rossland's approximation, we determine solar radiation and the activation energy describing the chemical reaction. By using suitable transformation, the mathematical modeling of the determinate flow can provide the set of non-linear differential equations. With the help of different parameters, we obtain a graphical interpretation of the motile density, local Nusselt number and Sherwood number. As an outcome of the stretching parameter and Prandtl number the temperature of the tangent hyperbolic liquid declines. By increasing the thermophoresis and magnetic parameter the nano fluid concentration initiates to ascend directly. The microorganism profile is found to be increasing for improving values of power law index parameter, while an opposite behavior can be observed for bio-convective Lewis number.

Effects of extended surfaces on heat transfer in buoyancy-driven flow in a square cavity

The finite element method is implemented to determine solutions for buoyancy-driven flow in a square cavity. We consider cases with no extended surface, only one extended surface, and an extended surface on walls opposite and adjacent to the cold wall. An investigation of the Péclet number provides an estimate for the amount of artificial diffusion to be added to the Boussinesq and heat transfer equations for stable numerical solutions to be obtained. The importance of the characteristic length on the flow in the square cavity is investigated in detail. We show grid convergence by computing the grid convergence index (GCI). The impact of the boundary conditions and extended surfaces on the isotherms, velocity streamlines and flux are plotted and discussed. We find that the case with insulated boundary conditions on the sidewalls gives a 31 and 33 percent decrease in the flux when we have two and three extended surfaces, respectively.

Surface network and drainage network: towards a common data structure

The surface network is an application of the Morse-Smale complex to digital terrain models connecting ridges and thalwegs of the terrain in a planar, undirected graph. Although it provides a topological structure embedding critical elements of the terrain, its application to morphological analysis and hydrology remains limited mainly because the drainage network is the most relevant structure for analysis and it cannot be derived from the surface network. The drainage network is a directed, hierarchical graph formed by streams. Ridges of the surface network are not equivalent to drainage divides, which are not contained in the drainage network, and there is no direct association between thalwegs and streams. Therefore, this paper proposes to extend the surface network into a new structure that also embeds the drainage network. This is done by (1) revising the definition of ridges so that they include drainage divides and (2) assigning a flow direction to each thalweg, taking into account spurious depressions to avoid flow interruption. We show that this extended surface network can be used to compute the flow accumulation and different hydrographic features such as drainage basins and the Strahler order. The drainage network extracted from the extended surface network is compared to drainage networks computed with the traditional D8 approach in three case studies. Differences remain minor and are mainly due to the elevation inaccuracy in flat or slightly convex areas. Hence, the extended surface network provides a richer data structure allowing the use of a common topological data structure in both terrain analysis and hydrology.

Effects of vertical coil springs on the performance of solar air heaters: Experimental study

Using extended surfaces or turbulators on the absorber plate (AP) is one of the great ways to enhance the thermal performance of solar air heaters (SAHs). Although a large number of studies have been conducted in this field, new geometries are still being proposed to improve the tradeoff between heat transfer enhancement and corresponding blowing power penalty. Coil springs are new offerings as turbulators, and the scientific literature currently lacks a parametric study to address the benefits of using such extended surfaces. To cover this gap, an experimental analysis of the AP equipped with vertical coil springs is carried out. The effects of different geometrical factors (coil height, coil pitch, coil diameter, and wire diameter) at three different levels are investigated for Reynolds number ranging from 5867 to 23471. One of the most important findings of this research is that, unlike most other turbulators, the heat transfer enhancement obtained using CSs is often greater than the resulting pressure drop. Therefore, the overall performance index is found to be always higher than unity, reaching a maximum value of 2.98 for the case with a coil diameter of 10 mm at Re = 5867. It is worth mentioning that upon varying the coil height from 3 mm to 9 mm, the highest Nusselt number and best overall performance are achieved at 6 mm. It is found that the overall performance of SAH declines by increasing both the coil pitch and the coil diameter. Comprehensive correlations are developed considering the effects of all geometrical parameters. The results predicted by the correlations match well with the experimental data with average errors within ± 10%.